Generators In Thailand

[genset]

This is quite a lengthy post… so please sit back and relax.

I've taken some time to read a number of threads in the Thai Visa Forums discussing the availability, operation and certain technical aspects of electrical generators in Thailand.

The aim of this post is to collate some of the questions previously posed into a single thread and offer additional information for anybody considering the purchase of a generator. I hope that this thread will also serve as a focal point for future generator related questions or comments for the benefit of all interested readers.

Regardless of size, a comprehensive range of generators are available in Thailand; from cheap and nasty, to the best that money can buy… in the last 12 months I have had meetings with a number of major metropolitan generator distributors and OEM assemblers in an attempt to better understand the generator market in Thailand, with a view to rolling out a comprehensive service in 2011.

Most of the products produced by big name engine and alternator manufacturers are imported and available in Thailand; Caterpillar, Cummins, Lister, Deutz, Perkins, Volvo, Scania and John Deere engines… Leroy Somer, Mecc Alte Spa and Stamford alternators to name a few… they're all available, if you're willing to pay the price; and after import duty, distributor mark up and VAT, they're not cheap.

We all know that the average expatriate in Thailand is a thrifty species; we invariably want European or American quality at a Thai price, but during the occasional sane moment, most of us still realize that we do actually get what we pay for in this life… My NZ neighbour (hi John…) is quite vocal on the locally manufactured items he's purchased, that have gone t*ts up in the last couple of years. He's so anxious to purchase quality items that he resembles a pack horse each time he returns from NZ or AU.

Having trawled extensively through the domestic generator market in an attempt to sort the wheat from the chaff, I will follow this post with examples of a line of generators currently available in Thailand. They represent neither the best, nor the worst generators available in Thailand, I have chosen them because in my opinion, they offer a good combination of quality and reliability at a reasonable and realistic price.

For the purpose of this post and in the interest of clarity; an alternator is the AC power generating portion, of what is commonly referred to as a 'generator'. Engine, refers to the mechanical power source, directly or indirectly driving the alternator, and generator refers to the combination of the two individual component parts.

What follows is an attempt to explain common generator terminology and identify some important aspects of generator operation and control.

Diesel or petrol (gasoline) powered generator engines, what's the difference and which one is the best option…?

• A diesel engine burns less fuel than a petrol engine performing the same work, due to the engine's high efficiency.
• A diesel engine has no high-tension electrical ignition system to attend to, resulting in high reliability and easy adaptation to damp environments.
• A petrol engine uses a spark plug to ignite a fuel/air mixture in the combustion chamber, driving a piston which powers the crankshaft. A diesel engine uses the heat of compression alone to initiate ignition and achieve the same effect.
• The life of a diesel engine is generally about twice as long as that of petrol engines,due to the increased strength of parts used, also because diesel fuel has better lubrication properties than petrol.
• Diesel fuel is considered safer than petrol in many applications. Although diesel fuel will burn in open air using a wick, it will not explode and does not release a large amount of flammable vapour.
• The carbon monoxide content of diesel engine exhaust is minimal as opposed to the high carbon monoxide content of petrol exhaust.
• Petrol driven generators are generally used to drive alternators up to 10Kva in size.
• Increased fuel economy, lower engine speeds and overall reliability make diesel the preferred choice for generator engines driving alternators over 10Kva in size.

What's the difference between direct drive and belt driven generators?

• A direct drive generator has the alternator bolted directly to the flywheel of the engine, in this configuration the alternator is single bearing.
• Direct drive is the most efficient method of driving an alternator.
• A twin bearing alternator with pulley is required if the alternator is to be belt driven. Depending on the available RPM of the engine and whether the alternator is 2 or 4 pole, a gearbox may also be required to achieve the correct RPM to drive the alternator.
• Belt driven alternators may be up to 50% less efficient than direct drive.

Alternators; 2 pole or 4 pole, what does this mean and what's the difference...?

• 'Pole' refers to the permanent or (more commonly) electro magnets mounted on the rotor within the alternator. A 2 pole alternator has 2 magnets, a 4 pole alternator; surprise, surprise… has 4.

Engine RPM, why do some generators operate at 1500rpm, others at 3000rpm (not to mention 1800, 3600rpm and 4500rpm etc…)?

• Single phase utility supply in Thailand is 220v @ 50Hz, the phase to phase voltage of three phase utility supply is 380v @ 50Hz.
• The frequency of a generator supply is dictated by the speed of alternator rotation.
• For a 2 pole alternator 600rpm = 10Hz, for a 4 pole alternator 300rpm = 10Hz.
• Thus a single phase 2 pole alternator must rotate at 3000rpm to generate 220v @ 50Hz (If this generator were in the US, it would rotate at 3600rpm for 60Hz). A three phase 4 pole alternator with twice the number of magnet poles only has to rotate at half the speed of the 2 pole alternator to generate the same voltage and frequency, 1500rpm would generate 220v (phase to neutral) and 380v (phase to phase) @ 50Hz (and again, in the US, it would rotate at 1800rpm for 60Hz).

I've seen some generators rated in Kva and others in Kw… What's the difference?

• Kva (Kilovolt Ampere) relates to 'apparent power' and Kw (Kilowatt) to 'actual power', the difference is related to Power Factor, and is a consideration when part of the load is comprised of AC motors in appliances such as refrigerators, ac units, well pumps etc.
• As most homes contain appliances such as this, typically, we will calculate the maximum Kw rating of a generator by multiplying the Kva value by a power factor of 0.8 to take the motors into account; e.g. 30Kva x 0.8 = 24Kw... this is the maximum available power, on which you should base your load calculation.
• If you are technically minded and would like to read more about the difference between Kva and Kw the following is a good article; http://rep.mgeups.com/edg/edg/technote/kw.pdf

What is an AVR and how does it work?

• Electronic voltage regulation is finding its way into smaller and smaller generator sets these days.
• It is still common for the voltage of small portable generators, to be regulated by a capacitor which will regulate the generator voltage within 5 to 10% of that required. An electronic AVR (automatic voltage regulator) is a far better option and will regulate the voltage within 1 to 2% or better.
• An AVR works by converting a small amount of the generator AC voltage to DC current (once the generator is at full voltage).
• This current is inversely proportional to the generators output voltage (the higher the voltage output of the generator, the less DC current the voltage regulator produces).
• AVRs are normally adjustable allowing voltage to be accurately set when the generator is running at full speed with no load. When a load is added to the generator, the output voltage will drop a little. The AVR instantly compensates by increasing the amount of DC current to the field coils, raising the voltage back to its pre-set level and preventing voltage drop. This is especially useful for motors requiring a surge of power on start up, such as those found in refrigerators and air conditioning units etc.
• With a constant, non variable load on the generator, the voltage regulator produces just enough DC current to keep the generator producing the correct output voltage.

Generator maintenance… do I really need to service this thing…? My mates genny has been running non stop for 5 years and all he does is fill her up every day or two…

• The short answer is yes…! A good quality generator represents a significant capital investment. With regular periodical maintenance, it should give you years of reliable service. As with any type of engine, the longer you ignore maintenance the more serious and costly the inevitable problems will be.
• You (or a diesel engineer) should carry out a full service (change oil, change oil filter, change fuel filter, clean or change air filter, drain and replace engine coolant, check fan belt for wear and tension) annually or every 500 hours, whichever comes first.
• Given the average ambient temperature in Thailand, I would recommend the use of SAE 15W-40 diesel engine oil.
• Always use a 50/50 mix of good quality ethylene glycol or propylene glycol coolant with water, DO NOT use water alone. Glycol based coolants (commonly referred to as anti-freeze, do not only offer low temperature protection (but also improve cooling qualities in high temperature environments. Using water alone may cause scaling, cavitation, iron corrosion and foaming which may in turn affect engine performance, reliability and service life.

Brushes…Brushless…? What does this mean and what's the difference?

• Whether an alternator incorporates brushes or not in its design, relates to the manner by which DC excitation voltage is transferred to the rotor field windings. The rotor field windings are mounted on a shaft (the rotor) which turns inside the stationary outer casing containing the output windings (the stator).
• In the majority of alternators the magnets on the rotor are not permanent magnets, they are electro magnets which are activated when DC voltage (excitation voltage) passes through the windings around them.
• An alternator with brushes transfers DC voltage via stationary carbon brushes to slip rings on the rotor shaft then onto the rotor field windings.
• Some brushless alternators feature an exciter coil which is a mini alternator normally mounted on the rear of the rotor. DC voltage from the AVR is fed into the exciter coil, stimulating the production of AC voltage, this passes through a rotating rectifier arrangement, converting the AC voltage back into DC voltage and on to the rotor field windings.
• Whichever method is used, the DC voltage passes through the rotor field windings and activates the electro magnets. As the electro magnets rotate, they induce AC voltage in the stator windings and power is produced, more information on how an alternator produces AC power can be found here http://www.generatorsolutions.org/#/gen-ac-power/4534128464

My other mate… runs his house on a portable genny… I've seen them for sale in the local hardware store; Sod it, I'm going to buy one of those things…

• A portable generator may indeed be just what you need… but if you want a reliable standby power source for your home or business that will stand the test of time and do the job properly, it is imperative that you size the generator correctly before you jump in and buy one.
• Ideally, your generator should be able to handle the full load of your home or business (or everything you wish to power) at approx 70 to 80% of the alternators maximum load rating.
• So, if (with every electrical appliance you wish to operate turned on), your home/business draws a total of 45amps; a 10Kw (approx 12Kva) generator would be an ideal size.
• Assuming your home/business uses a single phase supply, the figure of 10Kw is calculated as follows; 220v x 45amps x 0.8 power factor/1000 = 7.92 or 8Kw, this is your maximum load in Kw. An 8Kw load is 80% of the maximum load rating of a 10Kw generator, which is thus the optimum size generator for a 45amp load.
• More information on generator sizing can be found here http://www.generatorsolutions.org/#/sizing/4534128467
• This may seem a tad convoluted, but with good reason. Operating your generator at between 70 and 80% of it's maximum load rating will burn less fuel, create less noise, reduce engine wear and increase the engine life, allow for growth in your electrical needs (the purchase of an additional TV, fridge etc) and most importantly, reduce the likelihood of damage to, or catastrophic failure of the alternator.
• As the alternator reaches its maximum rated output, the temperature within the alternator windings will rise dramatically. The thermal insulation of every alternator is rated according to its ability to withstand the heat generated as an alternator begins to overload (this is what happens every time you load any generator to the gills, or continuously operate a generator at close to its maximum rated output).
• If an overload is sustained, the insulation will eventually fail and the alternator will short and burn out (unless the over current trips the generator breaker (if fitted) and saves the alternator), this is normally accompanied by a mass of sparks and black, acrid smoke, pouring out of the alternator air vents.
• Depending on the degree of damage; rewinding the alternator (time consuming and relatively expensive), or simply changing it out for a new alternator (again, an expensive and time consuming exercise) are the only options available.
• Taking the time to calculate the load requirement of your home/business and correctly selecting a generator based on the aforementioned calculation is highly recommended. It is an economic blunder to simply buy a portable generator just because it's cheap… a thoughtful selection process will not only save you time and money, but ensure that you get the best out of your generator investment over the long term.

How do I connect the generator to my distribution board…?

• If you are purchasing a generator as a standby power source for your home, the connection between the generator and your consumer unit/distribution board MUST be made through a manual or automatic transfer switch (I would recommend these connections be made by a qualified electrician). Under no circumstances should you ever attempt to connect the generator directly to your consumer unit/distribution board.
• Connecting the mains and generator supply simultaneously requires a complex synchronization process, but this is an expensive option and not required for general automatic mains failure use.
• More information on how a transfer switch works can be found here http://www.generatorsolutions.org/#/controls/4534128482

All generators fall into one of four distinct categories (ratings) according to use (as defined in ISO 8528-1:2005). Each category is listed below together with examples of generator types for home use and other applications (petrol and diesel driven versions only).

Emergency Standby Power (ESP) – Variable Load - 200 hours per year.

• Light duty, lightweight and portable (tubular frame design or the like).
• Single cylinder, air cooled engine.
• Predominantly petrol driven, although diesel versions are becoming more common (and are slightly more expensive).
• Single phase, 2 pole alternator driven at 3000/4600rpm depending on size, for 50Hz.
• May feature a low oil pressure shutdown switch.
• Recoil hand starter/crank starter or 12v DC electric start.
• Generally feature alternators up to 10Kva/8Kw in size and are designed to produce up to the alternators maximum rated output for 200 hours a year with no overload capacity.
• Capacitor voltage regulation (5 to 10%) or electronic AVR on more expensive models (1 to 2% or better).
• Power is distributed via on board plug sockets. This type of generator is not designed (with one or two notable exceptions) to operate in combination with an automatic transfer switch.
• Common applications; static construction sites/work tool power source, RV standby power, emergency lighting supply, etc.

Limited Time Running Power (LRP) (commonly referred to as Standby Power) – Constant Load - 500 hours per year.

• Heavier duty, mounted on a chassis/skid, permanent installation.
• Multiple cylinder, diesel powered, water cooled engine (intercooler and/or turbo may feature on larger engines).
• Single or three phase, 2 or 4 pole alternator driven at 3000 or 1500rpm respectively for 50Hz (certain types of alternator may be optionally configured as either single or three phase).
• May feature low oil pressure, high temperature and low coolant level shutdown switches.
• 12 or 24v DC electric start (depending on size).
• Generally feature alternators in the 10 to 30Kva/8 to 24kw range depending on the capability of the engine, alternator insulation grade etc, and are designed to produce up to their maximum rated output for 500 hours a year with no sustained overload capacity.
• Alternator overload protection is provided and power is distributed, via a generator mounted circuit breaker.
• Voltage regulation provided by electronic AVR.
• Will normally feature an electronic control panel with additional protections/alarms (low/high frequency, low/high voltage, under/over speed, low oil pressure, high temperature, low coolant level, low fuel level etc).
• May feature a remote start option and be compatible with an Automatic Transfer Switch.
• Common applications; a generator permanently installed as a standby/secondary source of power for a mid sized home or business and rated to operate for the average duration of a utility power outage.

Prime Power (PRP) – Variable Load - Unlimited Hours

• Engine and alternator features are as per the LRP rating; but as reliability and power generating demands increase, the tolerance of manufactured materials and assembly of component parts must increase.
• Unlimited run time; a prime power rated generator may supply up to it's maximum rated output 24hrs a day on a variable load. Typically, a 10% overload is permitted for up to one hour in any 12hr period.
• Common applications; a generator permanently installed as a prime source of power in place of a utility power supply (e.g. a remote location with no utility supply) and rated to produce up to the alternators maximum rated output for an unlimited period of time.

Continuous Power (COP) – Constant Load - Unlimited Hours

• Engine and alternator features as per the PRP rating; but as reliability and power generating demands increase, the tolerance of manufactured materials and assembly of component parts must increase.
• Unlimited run time; a continuous power rated generator may supply its continuous rated output 24hrs a day to a constant (base) load and no overload is permitted.
• Common applications; a generator permanently installed and synchronized to feed power into and support the national grid supply and rated to produce the alternators maximum rated output for an unlimited period of time.

After deciding on a line of generators that I felt offered the best quality/price combination, I contacted the manufacturer and they agreed to allow me to import their machines into Thailand beginning 2011. Although generators up to 375Kva in size are available from the manufacturer, for most people, the first two categories; Emergency Standby Power and Limited Time Running Power, will be of interest and they will therefore be my focus.

That doesn't help much if you're in the market for a decent generator today of course... In an attempt to provide an interim solution to the availability and supply of good quality generators for the expatriate community, I decided to reach out to one of their existing distributors.

There are two existing distributors in Thailand, I have met with both and established a good relationship with one in particular. They have agreed (in lieu of a commission payment to me), to offer these generators to the expatriate community, at a much lower price than their competitor. Lower in fact, than the price they are available to Thai nationals walking in off the street…imagine that..! One stipulation is that to receive the prices posted below, all referrals to the distributor in question should come through my website.

I will not receive any commission or payment in kind for these referrals… It may seem a little crazy for me to promote these generators for no financial gain, but until such time as I begin to import and sell this line of generators myself in 2011; This arrangement will allow me to establish a relationship and network with Thai distributors, raise the profile of these generators in Thailand, raise the profile of my website and hopefully present the expatriate community here, with an opportunity to purchase a quality product at a fair price, a win, win situation for all concerned I hope.

Congratulations if you've managed to read to the end of this post… my eyeballs are ready to leap out of my head and roll for cover at the thought of me typing any more to be honest…

More information on my website @ www.generatorsolutions.org and you can contact me directly @ [email protected]

If you decide to respond to this post, please delete my original post from your reply, or we could spend all day scrolling…

Regards,

Genset

[Artisi]

Excellent post, well put together in a logical, precise and informative manner - trust those in need of a genset take the time to read it carefully.

I think it would be good if the "powers that be" could make this a Forum topic so it is not lost in with the hundreds of other postings.

[tjo o tjim]

Nice write-up; you managed to cover a number of difficult topics in plain language.

On these little gensets, what level of leading power factor can they support? Too many of the electronic AVR systems seem to choke on minor leading power factor (0.97 capacitive PF).

[joncl]

One of the issues facing many people (me included) and maybe Genset might like to explain this to us in more details is;

1. Not all generator sets will power / recharge nor work with a UPS line (AC-AC), where a DC based inverter system, will work due to their configuration (DC-AC).

2. Will your KDE6700TA - Emergency Standby Generator recharge and can it be used with an UPS inline (AC-DC-AC) or does it have to be removed like many other generator sets require you to do?

We use UPS's here on all our system as our first line of defense for brownouts / blackouts. One thing that has annoyed me is the need to isolate the UPS from the generator set when the UPS's fail after 2 hours. Having said that in the last 12 months the generator has only been used for 2 hours as the UPS catch most of the brownouts.

[genset]

Nice write-up; you managed to cover a number of difficult topics in plain language.

On these little gensets, what level of leading power factor can they support? Too many of the electronic AVR systems seem to choke on minor leading power factor (0.97 capacitive PF).

Thank you for your comments.

The answer, in a nutshell, is very little. Regardless of who manufactures a generator AVR, they are all designed around the same principle.

There are others in the forum (Crossy and Elkangorito to name but two), who are better qualified to talk about the reasons why leading power factor can be an issue for electronic AVRs, but I would like to refer you to a white paper, written by Gary Olson, Director, Power Systems Development at Cummins Power Generation.

The first two pages of this document explain very clearly 'the impact of leading power factor on synchronous alternators'.

Genset

Impact_of_leading_power_factor_on_synchronous_alternators.pdf

[genset]

One of the issues facing many people (me included) and maybe Genset might like to explain this to us in more details is;

1. Not all generator sets will power / recharge nor work with a UPS line (AC-AC), where a DC based inverter system, will work due to their configuration (DC-AC).

2. Will your KDE6700TA - Emergency Standby Generator recharge and can it be used with an UPS inline (AC-DC-AC) or does it have to be removed like many other generator sets require you to do?

We use UPS's here on all our system as our first line of defense for brownouts / blackouts. One thing that has annoyed me is the need to isolate the UPS from the generator set when the UPS's fail after 2 hours. Having said that in the last 12 months the generator has only been used for 2 hours as the UPS catch most of the brownouts.

This is again related to the issue of leading power factor raised by Artisi and harmonics/wave form distortion. If you have used other generators to power your UPS backup systems (how many units?) with no succes, the likelihood of the KDE6700TA fairing any better is minimal. As I mentioned in the last post, all AVRs are designed around the same principle. Some UPS sytems operate ok with generators I have installed, and others experience problems.

Page two of the document attached to this post addresses the specific issue of why, under certain conditions, UPS systems fail to operate and/or the generator shuts down. The most common result of a heavy capacitive load is an increase in generator voltage, if fitted, the electronic generator control panel constantly monitors the generator voltage and will carry out an overvoltage shutdown and stop the machine.

Genset

Impact_of_leading_power_factor_on_synchronous_alternators.pdf

Edited October 31, 2009 by genset

[Naam]

KDE16SS – LRP Generator (Standby power 14.5Kva) – PRP Generator (Prime power 12Kva)

* Significant step up in performance and reliability. Static set, in Super Silent canopy, on skids, weighs 790Kg.

* Manufactured to CE standards (EU Machinery Directive 98/37EC and EU Low Voltage Directive 2006/95/ EEC).

* 14.5Kva (11.6Kw) (LRP) or 12Kva (9.6Kw) (PRP), suitable for a wide range of applications. This set will easily power a large home, with AC's, and numerous electronic appliances.

thanks Genset. very informative thread although "large home" is relative. my question is specific for my home which has 19 powerhungry aircons distributed evenly over three phases (only a third of them are running normally). are there no three-phase gensets in the range 15-25Kva available? the alternative would be to selectively wire the most important aircons and rooms as well as the kitchen to a single phase which would be fed by the generator.

i also don't understand why UPSs have to be disconnected when the generator is in use. i installed three different inverter sets (each with 2 batteries totalling 320 Ah) which, in case one or more phases are gone, power our water pumps, my study with various computers, my wife's study with computer and TV as well as my TV-room. besides the electronic equipment and lights two ceiling fans are connected.

is any kind "electrical soul" able to answer my question? Crossy? ElKangorito?

thanks in advance. presently i don't see the need of installing a generator but the time might come when i think it is necesssary and i want to be prepared for this eventuality.

[david96]

KDE16SS – LRP Generator (Standby power 14.5Kva) – PRP Generator (Prime power 12Kva)

* Significant step up in performance and reliability. Static set, in Super Silent canopy, on skids, weighs 790Kg.

* Manufactured to CE standards (EU Machinery Directive 98/37EC and EU Low Voltage Directive 2006/95/ EEC).

* 14.5Kva (11.6Kw) (LRP) or 12Kva (9.6Kw) (PRP), suitable for a wide range of applications. This set will easily power a large home, with AC's, and numerous electronic appliances.

thanks Genset. very informative thread although "large home" is relative. my question is specific for my home which has 19 powerhungry aircons distributed evenly over three phases (only a third of them are running normally). are there no three-phase gensets in the range 15-25Kva available? the alternative would be to selectively wire the most important aircons and rooms as well as the kitchen to a single phase which would be fed by the generator.

i also don't understand why UPSs have to be disconnected when the generator is in use. i installed three different inverter sets (each with 2 batteries totalling 320 Ah) which, in case one or more phases are gone, power our water pumps, my study with various computers, my wife's study with computer and TV as well as my TV-room. besides the electronic equipment and lights two ceiling fans are connected.

is any kind "electrical soul" able to answer my question? Crossy? ElKangorito?

thanks in advance. presently i don't see the need of installing a generator but the time might come when i think it is necesssary and i want to be prepared for this eventuality.

A UPS should not be disconnected when the generator supply is on line.

The purpose of a UPS to to supply power to essential equipment, eg, computers etc in the period when the normal supply fails and the emergency generator connects to the load though an ATS. The period is nomally 5 secs of mains failure then the genset starts and goes on line. Total time about 20secs.

Normally most UPS systems will supply about 6 mins of power. This figure is when they are new, batteries deteriorate with age and after 2 years should be checked and replaced. Larger units are available for specific purposes and have larger battery back up and will supply power for longer.

Switchboards may be connected for essential and non essential power. Essential power is supplied by the mains or generator, non essential power is supplied only by the mains.

[genset]

KDE16SS – LRP Generator (Standby power 14.5Kva) – PRP Generator (Prime power 12Kva)

* Significant step up in performance and reliability. Static set, in Super Silent canopy, on skids, weighs 790Kg.

* Manufactured to CE standards (EU Machinery Directive 98/37EC and EU Low Voltage Directive 2006/95/ EEC).

* 14.5Kva (11.6Kw) (LRP) or 12Kva (9.6Kw) (PRP), suitable for a wide range of applications. This set will easily power a large home, with AC's, and numerous electronic appliances.

thanks Genset. very informative thread although "large home" is relative.

Yes, it is relative, my example of each category was offered as a rough guide only. If you want to be more specific regarding the selection of a suitably sized generator for your own home, I would refer you to the following paragraph from my original post. You will need to first determine your load requirement and then size your generator based on that figure:

My other mate… runs his house on a portable genny… I've seen them for sale in the local hardware store; Sod it, I'm going to buy one of those things…

• A portable generator may indeed be just what you need… but if you want a reliable standby power source for your home or business that will stand the test of time and do the job properly, it is imperative that you size the generator correctly before you jump in and buy one.
  
• Ideally, your generator should be able to handle the full load of your home or business (or everything you wish to power) at approx 70 to 80% of the alternators maximum load rating.
  
• So, if (with every electrical appliance you wish to operate turned on), your home/business draws a total of 45amps; a 10Kw (approx 12Kva) generator would be an ideal size.
  
• Assuming your home/business uses a single phase supply, the figure of 10Kw is calculated as follows; 220v x 45amps x 0.8 power factor/1000 = 7.92 or 8Kw, this is your maximum load in Kw. An 8Kw load is 80% of the maximum load rating of a 10Kw generator, which is thus the optimum size generator for a 45amp load.
  

my question is specific for my home which has 19 powerhungry aircons distributed evenly over three phases (only a third of them are running normally). are there no three-phase gensets in the range 15-25Kva available?

19 aircons... ok... doesnt the hotel you live in have a decent generator already...? Only kidding...there are indeed three phase gensets availabe in the 15-25kva range, but they are more costly as they are heavier duty, slow running (1500rpmk) gensets in the same range as the KDE16SS, the KDE20SS3 is one such model. Once you have determined your load requirement (remember to use starting wattage for your aircons in your calcuation), drop me a line and I will refer you to a specific size and model suitabe for your needs.

the alternative would be to selectively wire the most important aircons and rooms as well as the kitchen to a single phase which would be fed by the generator.

i also don't understand why UPSs have to be disconnected when the generator is in use. i installed three different inverter sets (each with 2 batteries totalling 320 Ah) which, in case one or more phases are gone, power our water pumps, my study with various computers, my wife's study with computer and TV as well as my TV-room. besides the electronic equipment and lights two ceiling fans are connected.

You shouldnt have to disconnect your UPS when the generator is in use, but under certain conditions, the UPS may contribute to the malfunction of the AVR resulting in generator shut down and/or non operation of the UPS system. Please read page two of the attached PDF file regarding UPS use with a synchronous alternator.

is any kind "electrical soul" able to answer my question? Crossy? ElKangorito?

thanks in advance. presently i don't see the need of installing a generator but the time might come when i think it is necesssary and i want to be prepared for this eventuality.

The superior man, when resting in safety, does not forget that danger may come. When in a state of security he does not forget the possibility of ruin. When all is orderly, he does not forget that disorder may come. Thus his person is not endangered, and his States and all their clans are preserved.

Confucius

Chinese philosopher & reformer (551 - 479 BC)

Impact_of_leading_power_factor_on_synchronous_alternators.pdf

Edited October 31, 2009 by genset

[genset]

A UPS should not be disconnected when the generator supply is on line.

I believe Naam is referring to the question posed in post No8. Please read page 2 of the document I posted in answer to that question and for more information about 'leading power factor' and how, under certain conditions, it may affect UPS and generator operation.

The purpose of a UPS to to supply power to essential equipment, eg, computers etc in the period when the normal supply fails and the emergency generator connects to the load though an ATS. The period is nomally 5 secs of mains failure then the genset starts and goes on line. Total time about 20secs.

Normally most UPS systems will supply about 6 mins of power. This figure is when they are new, batteries deteriorate with age and after 2 years should be checked and replaced. Larger units are available for specific purposes and have larger battery back up and will supply power for longer.

Switchboards may be connected for essential and non essential power. Essential power is supplied by the mains or generator, non essential power is supplied only by the mains.

Edited October 31, 2009 by genset

[david96]

A UPS should not be disconnected when the generator supply is on line.

I believe Naam is referring to the question posed in post No8. Please read page 2 of the document I posted in answer to that question for more information about 'leading power factor' and how it affects UPS and generator operation.

The purpose of a UPS to to supply power to essential equipment, eg, computers etc in the period when the normal supply fails and the emergency generator connects to the load though an ATS. The period is nomally 5 secs of mains failure then the genset starts and goes on line. Total time about 20secs.

Normally most UPS systems will supply about 6 mins of power. This figure is when they are new, batteries deteriorate with age and after 2 years should be checked and replaced. Larger units are available for specific purposes and have larger battery back up and will supply power for longer.

Switchboards may be connected for essential and non essential power. Essential power is supplied by the mains or generator, non essential power is supplied only by the mains.

Supply Authority power factor can usually be between 0.6 and .9 lagging. A syncronous motor

can be run at a PF of 1.0. A sychronous motor can be used for PF correction.

Capacitors are normally used for PF correction eg, to improve an existing PF of 0.7 to perhaps

0.9. O.95 is the economical limit.

In my experience you will not come across leading power factor in practice, it will be lagging as most loads are inductive not capacitive.

( Some small generators do have problems with their waveform when used to supply electronic equipment and the manufacturers advice should be obtained.)

[david96]

One of the issues facing many people (me included) and maybe Genset might like to explain this to us in more details is;

1. Not all generator sets will power / recharge nor work with a UPS line (AC-AC), where a DC based inverter system, will work due to their configuration (DC-AC).

2. Will your KDE6700TA - Emergency Standby Generator recharge and can it be used with an UPS inline (AC-DC-AC) or does it have to be removed like many other generator sets require you to do?

We use UPS's here on all our system as our first line of defense for brownouts / blackouts. One thing that has annoyed me is the need to isolate the UPS from the generator set when the UPS's fail after 2 hours. Having said that in the last 12 months the generator has only been used for 2 hours as the UPS catch most of the brownouts.

If your generator supplies the correct voltage, frequency and waveform the UPS should be connected to supply at all times as this is used to supply power to your essential equipment in the case of power supply failure. Normally this would be no more that 1 minute, that is until your standby genset goes on line.

We are looking here at a standard genset, auto start on mains failure and with a run on time of usually 15 minutes after power has been restored.

A typical genset would be 220/380 to 240/415Volts, 50Hz, 4 pole 1500 rpm.

As far as an UPS is concerned there is no difference between the mains supply and the generator supply.

[Gary A]

I was determined to have a generator to power everything except the hot water shower, (5,200 watt), and the air conditioner. I have a 30 HP diesel tractor with a PTO or an 11 HP diesel Kubota to drive a generator. I have since given up on the project. I already have a small gasoline powered generator. I have found that I can make the electric come back on by using the small generator. At least it seems that way. The outages are normally quite brief. By the time I run the extension cords and get the generator running, the power comes back on.

I have now decided that I want to use a battery backup system. Just like a computer UPS but much larger. It would normally use the main to stay charged but in case of a prolonged power failure, a generator could also be used to charge the batteries. Much more expensive but automatic switching is very convenient. A capacity of about 1400 watts for a couple of hours would be enough.

Genset, are you able to put together a system like that?

[genset]

Supply Authority power factor can usually be between 0.6 and .9 lagging. A syncronous motor

can be run at a PF of 1.0. A sychronous motor can be used for PF correction.

Capacitors are normally used for PF correction eg, to improve an existing PF of 0.7 to perhaps

0.9. O.95 is the economical limit.

In my experience you will not come across leading power factor in practice, it will be lagging as most loads are inductive not capacitive.

Agreed, the discussion of leading power factor arose from one of the first questions posed. My experience is that it is not a major issue in general, but the PDF document is an interesting read regardless.

( Some small generators do have problems with their waveform when used to supply electronic equipment and the manufacturers advice should be obtained.)

Edited October 29, 2009 by genset

[genset]

I was determined to have a generator to power everything except the hot water shower, (5,200 watt), and the air conditioner. I have a 30 HP diesel tractor with a PTO or an 11 HP diesel Kubota to drive a generator. I have since given up on the project. I already have a small gasoline powered generator. I have found that I can make the electric come back on by using the small generator. At least it seems that way. The outages are normally quite brief. By the time I run the extension cords and get the generator running, the power comes back on.

I have now decided that I want to use a battery backup system. Just like a computer UPS but much larger. It would normally use the main to stay charged but in case of a prolonged power failure, a generator could also be used to charge the batteries. Much more expensive but automatic switching is very convenient. A capacity of about 1400 watts for a couple of hours would be enough.

Genset, are you able to put together a system like that?

I dont have any experience designing and installing large battery back up systems I'm afraid, but most portable generators such as the IG2000 and KDE6700TA models feature a DC output which may be of use to you.

[Naam]

naam: my question is specific for my home which has 19 powerhungry aircons distributed evenly over three phases (only a third of them are running normally). are there no three-phase gensets in the range 15-25Kva available?

genset: 19 aircons... ok... doesnt the hotel you live in have a decent generator already...? Only kidding...there are indeed three phase gensets availabe in the 15-25kva range, but they are more costly as they are heavier duty, slow running (1500rpmk) gensets in the same range as the KDE16SS, the KDE20SS3 is one such model. Once you have determined your load requirement (remember to use starting wattage for your aircons in your calcuation), drop me a line and I will refer you to a specific size and model suitabe for your needs.

the starting amps of the aircon compressors are indeed a problem. if taken fully into consideration i would have to select overkill kVa capacity. a solution would be to switch off all aircons with the individual brakers, start the generator and then switch on the aircons one by one. slightly tedious but effective.

something similar applies to the obvious much more expensive three-phase sets. wiring the essential consumers including aircons seems to be a simple and extremely cheap solution as in my case each aircon is on a proprietory circuit with an individual breaker.

my load calculation (for a rather comfortable solution) including a safety factor of 20% shows a total of 14 kilowatts, that means 20 kVa should suffice. the "el cheapo" alternative but still feasible solution including a 20% additional factor is ~10 kilowatts and perhaps a 15 kVa unit.

your opinion please Genset.

[Naam]

I was determined to have a generator to power everything except the hot water shower, (5,200 watt), and the air conditioner. I have a 30 HP diesel tractor with a PTO or an 11 HP diesel Kubota to drive a generator. I have since given up on the project. I already have a small gasoline powered generator. I have found that I can make the electric come back on by using the small generator. At least it seems that way. The outages are normally quite brief. By the time I run the extension cords and get the generator running, the power comes back on.

I have now decided that I want to use a battery backup system. Just like a computer UPS but much larger. It would normally use the main to stay charged but in case of a prolonged power failure, a generator could also be used to charge the batteries. Much more expensive but automatic switching is very convenient. A capacity of about 1400 watts for a couple of hours would be enough.

Genset, are you able to put together a system like that?

that's an easy one Gary. i have installed three systems each for continuous output of ~1,500 watts. got the inverters from India (cost each 225 US-dollars) and bought the batteries locally (two per system each 160Ah @ 4,300 Baht). the inverters switch automatically in milliseconds (computers and lights don't wink an eye) and of course have a built-in electronic charger. wiring inverter to batteries is childs play and done in a few minutes. a bigger problem is to connect the output to the locations you want if you own the average thai house with only half a dozen breakers

[Gary A]

I was determined to have a generator to power everything except the hot water shower, (5,200 watt), and the air conditioner. I have a 30 HP diesel tractor with a PTO or an 11 HP diesel Kubota to drive a generator. I have since given up on the project. I already have a small gasoline powered generator. I have found that I can make the electric come back on by using the small generator. At least it seems that way. The outages are normally quite brief. By the time I run the extension cords and get the generator running, the power comes back on.

I have now decided that I want to use a battery backup system. Just like a computer UPS but much larger. It would normally use the main to stay charged but in case of a prolonged power failure, a generator could also be used to charge the batteries. Much more expensive but automatic switching is very convenient. A capacity of about 1400 watts for a couple of hours would be enough.

Genset, are you able to put together a system like that?

that's an easy one Gary. i have installed three systems each for continuous output of ~1,500 watts. got the inverters from India (cost each 225 US-dollars) and bought the batteries locally (two per system each 160Ah @ 4,300 Baht). the inverters switch automatically in milliseconds (computers and lights don't wink an eye) and of course have a built-in electronic charger. wiring inverter to batteries is childs play and done in a few minutes. a bigger problem is to connect the output to the locations you want if you own the average thai house with only half a dozen breakers

I think I would wire two 10 amp breakers into the battery system permanently. The other breakers would simply go dead when the mains power fails. My wife is one of those Thais who thinks unplugging the small kitchen appliances saves power. She would know that when we are on battery power to leave them unplugged. If I had a couple of fans, a refrigerator, my computer and the lights, that would do fine.

[elkangorito]

the starting amps of the aircon compressors are indeed a problem. if taken fully into consideration i would have to select overkill kVa capacity. a solution would be to switch off all aircons with the individual brakers, start the generator and then switch on the aircons one by one. slightly tedious but effective.

something similar applies to the obvious much more expensive three-phase sets. wiring the essential consumers including aircons seems to be a simple and extremely cheap solution as in my case each aircon is on a proprietory circuit with an individual breaker.

my load calculation (for a rather comfortable solution) including a safety factor of 20% shows a total of 14 kilowatts, that means 20 kVa should suffice. the "el cheapo" alternative but still feasible solution including a 20% additional factor is ~10 kilowatts and perhaps a 15 kVa unit.

your opinion please Genset.

Doc. I've seen your installation & from memory, you have 3 or 4 switchboards grouped together.

This is not a good way to do things. I hate to tell you but you should have had only 1 switchboard from the beginning...and yes, it will be bloody big!

If you did have a "correct" installation (one switchboard), you may be able to easily fit "load shedding" contactors. What I'm trying to say is that if you had 1 switchboard for your circuit breakers, a "load shedding" panel (complete with phase failure equipment) would be an easy addition to your system. The only thing you would need to consider is if you want a "manual transfer switch" or an "automatic transfer switch". In any case, the transfer switch panel could be made to also accommodate the load shedding contactors.

[genset]

the starting amps of the aircon compressors are indeed a problem. if taken fully into consideration i would have to select overkill kVa capacity. a solution would be to switch off all aircons with the individual brakers, start the generator and then switch on the aircons one by one. slightly tedious but effective.

If you normally run all of your air conditioning units all of the time, I would stick with a load calculation based on the starting wattage of each individual a/c unit plus all your other electrical appliances. Your 'tedious but effective' suggestion of isolating each a/c circuit prior to generator startup and then turning them on one by one, may work initially; but the random on/off cycle of the a/c compressors as each room warms/cools/warms at a variable rate, may lead to a situation a few hours (or more) later where the cycles sync once more, the combined power requirement as the majority of your a/c compressors start simultaneously, on an undersized generator, will trip the generator breaker (overcurrent) or stall the set.

something similar applies to the obvious much more expensive three-phase sets. wiring the essential consumers including aircons seems to be a simple and extremely cheap solution as in my case each aircon is on a proprietory circuit with an individual breaker.

my load calculation (for a rather comfortable solution) including a safety factor of 20% shows a total of 14 kilowatts, that means 20 kVa should suffice. the "el cheapo" alternative but still feasible solution including a 20% additional factor is ~10 kilowatts and perhaps a 15 kVa unit.

If your total load requirement is 14Kw. Then 14Kw = 80% of 17.5Kw (22Kva rounded up) so a 22Kva generator would be the optimum size... It doesnt appear however, that your 14Kw load requirement was calculated using the starting wattage for all of your a/c units; if the 14Kw load was for your 19 a/c units alone (not including your other electrical appliances), it would mean an average starting wattage of just over 700watts per unit... this can't be correct, can it...?

your opinion please Genset.

Edited October 29, 2009 by genset

[david96]

Here is the website with information on UPS systems available in Thailand. Follow the links.

Single and Three phase units.

http://www.chloridepower.com/en-gb/Thailan...cts--Solutions/

[david96]

And this website may be useful for calculating generator size and power calculations on line.

http://www.macgen.com/calcul.html

[Naam]

If your total load requirement is 14Kw. Then 14Kw = 80% of 17.5Kw (22Kva rounded up) so a 22Kva generator would be the optimum size... It doesnt appear however, that your 14Kw load requirement was calculated using the starting wattage for all of your a/c units; if the 14Kw load was for your 19 a/c units alone (not including your other electrical appliances), it would mean an average starting wattage of just over 700watts per unit... this can't be correct, can it...?

of course i did not consider all aircon units for a rational but still comfortable solution all aircons together draw 28 kilowatts = >120 amps = minimum starting amps exceeding 250 amps! they would even overload my present three-pase connection of 3x30 amps even though i was told that in (amazing) Thailand i can overload by 100% continuously and 150% for "short time" but that is academic only but it happens 3-4 times a year when 14 or 15 aircons are running full blast from evening till next morning after i receive a message saying "tomollow no power flom 08.00 till 16.00 hrs because habb lepair erectricity our area".

what i considered is

kitchen: two huge fridges/freezers each 800 watts, one microwave 1200 watts and 250 watts lighting

my study: one aircon 13,000 btu 1100 watts and miscellaneous electronics 600 watts

wife's study: one aircon 13,000 btu 1100 watts and miscellaneous electronics plus TV 1000 watts

TV-room: one aircon 13,000 btu 1100 watts plus TV, sat-receivers, harddrive recorders 100 watts

master bedroom: one aircon 13,000 btu 1100 watts

pressurised water supply: two pumps each 800 watts

starting amps apply only to the fridges and one aircon as the aircons are switched on manually one by one

total: max 10 kilowatts

[genset]

of course i did not consider all aircon units for a rational but still comfortable solution all aircons together draw 28 kilowatts = >120 amps = minimum starting amps exceeding 250 amps! they would even overload my present three-pase connection of 3x30 amps even though i was told that in (amazing) Thailand i can overload by 100% continuously and 150% for "short time" but that is academic only but it happens 3-4 times a year when 14 or 15 aircons are running full blast from evening till next morning after i receive a message saying "tomollow no power flom 08.00 till 16.00 hrs because habb lepair erectricity our area".

what i considered is

kitchen: two huge fridges/freezers each 800 watts, one microwave 1200 watts and 250 watts lighting

my study: one aircon 13,000 btu 1100 watts and miscellaneous electronics 600 watts

wife's study: one aircon 13,000 btu 1100 watts and miscellaneous electronics plus TV 1000 watts

TV-room: one aircon 13,000 btu 1100 watts plus TV, sat-receivers, harddrive recorders 100 watts

master bedroom: one aircon 13,000 btu 1100 watts

pressurised water supply: two pumps each 800 watts

starting amps apply only to the fridges and one aircon as the aircons are switched on manually one by one

total: max 10 kilowatts

The KDE20SS3 is a Super Silent, 17Kva (13.6Kw) 3 phase set, same specs as the KDE16SS, but the former is 3 phase, rated current is 24.5amps per phase. For your information, I'll paste the specs and price tomorrow if I get a chance.

Edited October 30, 2009 by genset

[Naam]

The KDE20SS3 is a Super Silent, 17Kva (13.6Kw) 3 phase set, same specs as the KDE16SS, but the former is 3 phase, rated current is 24.5amps per phase. For your information, I'll paste the specs and price tomorrow if I get a chance.

thanks Genset. i think that unit would be perfect for my demands. the higher price for a three-phase unit might be compensated by the big advantage that power is not limited to certain areas. but i still have a problem understanding the calculation "3x24.5 amps = 13.6 kW".

24.5 amps @ 220 volts = 5390 kW x 3 = 16170 kW. do i miss something?

Edited October 30, 2009 by Naam

[genset]

The KDE20SS3 is a Super Silent, 17Kva (13.6Kw) 3 phase set, same specs as the KDE16SS, but the former is 3 phase, rated current is 24.5amps per phase. For your information, I'll paste the specs and price tomorrow if I get a chance.

thanks Genset. i think that unit would be perfect for my demands. the higher price for a three-phase unit might be compensated by the big advantage that power is not limited to certain areas. but i still have a problem understanding the calculation "3x24.5 amps = 13.6 kW".

24.5 amps @ 220 volts = 5390 kW x 3 = 16170 kW. do i miss something?

Hi Naam,

I should have given you the formula for calculating amps from Kw when using a 3 phase generator, my apologies.

Amps = (Kw x 1000) / (Voltage x Power Factor x 1.73 (the square root of 3 for a three phase supply)), therefore;

Amps = (13.6 x 1000) 13600 / (400 x 0.8 x 1.73) 553.6

Thus, 13600 / 553.6 = 24.5 amps per phase

Thanks for picking me up on this Naam, hope this clears up the confusion..

Genset

Edited November 29, 2009 by genset

[robm]

KDE6700TA - Emergency Standby Generator

• Mobile set, on wheels, sturdy, well built, weighs 193kg.
  
• Manufactured to CE standards (EU Machinery Directive 98/37EC and EU Low Voltage Directive 2006/95/EEC).
  
• 5Kva (4Kw), suitable for a wide range of applications.
  
• Generator is enclosed in a soundproof canopy, unit operates at 72db/7m on a full load.
  
• Electronic AVR voltage regulation.
  
• Brushless, self exciting, 2 pole alternator.
  
• Air cooled, single cylinder, vertical four stroke direct injection diesel engine.
  
• KDE6700TA operates at 3000rpm producing single phase, 220v @ 50Hz and delivering approx 20amps of usable power.
  
• Electric start, the set also features a digital control panel with a remote start facility.
  
• Set has ATS connections and is compatible for use with an automatic transfer switch. This enables completely automated operation in the event of a power failure or deep brown out to your home.
  
• 9.5 hours runtime when loaded and fully fuelled.
  
• Set must be grounded if used to power a grounded load.
  
• 12 months warranty.
  

Price including VAT from distributor;

KDE6700TA – 54,000 Thb

Dont want to dissapoint you,you seem to know what your talking about, but i purchased 1 off these generators not from you and had problems with it so changed it for another 1 and again had problems got refund in the the end had a different control panel on though,now purchased a kyoto bright orange genny run for 150 hrs so far no problems,

[Crossy]

Dont want to dissapoint you,you seem to know what your talking about, but i purchased 1 off these generators not from you and had problems with it so changed it for another 1 and again had problems got refund in the the end had a different control panel on though,now purchased a kyoto bright orange genny run for 150 hrs so far no problems,

It would be useful to all if you could briefly detail the issue you had with this unit, was it related to the control panel which you have now replaced?

[genset]

Dont want to dissapoint you,you seem to know what your talking about, but i purchased 1 off these generators not from you and had problems with it so changed it for another 1 and again had problems got refund in the the end had a different control panel on though,now purchased a kyoto bright orange genny run for 150 hrs so far no problems,

Hi RobM,

Not dissapointed, I appreciate your comments, there is no point in ignoring maintenance or reliability issues if they have occured. As with any product, there will always be occasions when defective units or operational/reliability issues are raised. I appreciate the opportunity to discuss it.

I dont know how long ago you purchased the generator, but the first generation KDE6700TA featured a different control panel as you mentioned, there were also problems with the fuel pump on some units. Prior to and in anticipation of CE Conformity Certification, both faulty aspects (the digital control panel and pump) of these machines were upgraded and that seems to have remedied the issues. I would hazard a guess that the machine you purchased was indeed a first generation model (perhaps old stock), it seems to fit the profile.

As you can see from the CE certificate for the KDE6700TA, it received certification in December 2007, units manufactured prior to that date, did not meet the EU low voltage and machinery directives. I am sorry to hear that you had a problem with the unit you purchased, but I do not feel that it reflects on the standard of the model KDE6700TA currently being manufactured by Kipor.

I am happy to hear that you were able to exchange the unit and subsequently get a refund. The distributor I have aligned with in Bangkok offers a 12 month warranty on all generators and are very attentive to requests by customers for warranty repairs or replacement of parts.

Genset

Edited November 29, 2009 by genset

[InterestedObserver]

In simple terms, a leading power factor will cause a synchronous generator internal voltage to increase. The electronic AVR will sense this increase in internal voltage and decrease the generator excitation. At some point the AVR will tend to loose control of the generator output voltage due to low excitation. This can be a huge problem when working with paralleled, load sharing generators. The generator kvar capacity curves will indicate a design leading power factor limit. A lagging power factor will reverse this tendency of the AVR to loose control.

UPS and electronic loads present a different problem, one of harmonics and waveform distortion from non-linear power supplies. Most cheap electronic AVRs use average sensing and the zero crossing point as a control reference. Since the voltage waveform is distorted, the reference point is not stable, the SCR gating signal is not stable, and the AVR output tends to fluctuate. A true rms sensing (digital) AVR may be required if this becomes a significant problem.

Residential electrical systems usually operate at a lagging power factor without significant UPS loads. If you have a leading power factor, then you usually have harmonic (waveform distortion) problems associated with a lot of non-linear loads.