Generators In Thailand

[genset]

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.

Hi InterestedObserver, your comments seem to correspond with those in my earlier post No10;

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.

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.

Mecc Alte techs tell me that harmonics and waveform distortion do indeed have a part to play (under certain conditions), with probems associated with UPS system use on a generator supply.

AVRs can be fairly pricey items, I use Mecc Alte Spa digital AVRs and they run around 400 sterling a pop...(not fitted on Kipor generators). A good 'budget' model is the Datakom AVR-5/10/12/20 range which can be retrofitted to most single or three phase alternators http://www.ipu.co.uk/engine_info.asp?id=232571

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.

[david96]

Here is an example of a standby generator system in a hospital ( Australia)

Main Switchboards were divided into essential and non essential loads.

2 x 875KVA 4 pole 50hz generators. Auto start on mains failure or undervoltage.

Generators connected to an ATS. Generators run in parallel (auto synronisation)

On line within 20 secs of mains failure, 20min run on time.

One of the areas supplied was the IT centre and it was equipped with a 20KVA

3 phase UPS which was designed to carry a fixed load for 30mins. This of course

was when the batteries were new and depended on the actual load being supplied.

There were numerous small UPS units supplying computers and medical monitoring

equipment.

Airconditioning was sequence started. There were numerous VSDs within the HVAC

system.

System PF was generally between 0.85 an 0.9

And there was never any problem with harmonics or voltage stability.

The UPS used on medical equipment did not have split mode power supplies as these

tended to bring up alarms on LIM units due to their high standing leakage current.

[genset]

Here is an example of a standby generator system in a hospital ( Australia)

Main Switchboards were divided into essential and non essential loads.

2 x 875KVA 4 pole 50hz generators. Auto start on mains failure or undervoltage.

Generators connected to an ATS. Generators run in parallel (auto synronisation)

On line within 20 secs of mains failure, 20min run on time.

One of the areas supplied was the IT centre and it was equipped with a 20KVA

3 phase UPS which was designed to carry a fixed load for 30mins. This of course

was when the batteries were new and depended on the actual load being supplied.

There were numerous small UPS units supplying computers and medical monitoring

equipment.

Airconditioning was sequence started. There were numerous VSDs within the HVAC

system.

System PF was generally between 0.85 an 0.9

And there was never any problem with harmonics or voltage stability.

The UPS used on medical equipment did not have split mode power supplies as these

tended to bring up alarms on LIM units due to their high standing leakage current.

Hi David96,

I appreciate your input and understand your point. I dont want this issue to become contentious, I see you have mentioned this in another previous post and would like to draw a line under it if I may.

Nobody is suggesting that you do not have experience of UPS systems (possibly numerous systems) that work faultlessly with a standby generator supply, or that your point is not valid. In post No9 I wrote; 'Some UPS sytems operate ok with generators I have installed, and others experience problems.' I further wrote in response to your comments, post No18; 'My experience is that it is not a major issue in general, but the PDF document is an interesting read regardless'.

That is to say, that not every UPS system operating on a generator supply will experience problems (I dont think that anybody is knocking the value of UPS systems here or suggesting that the problem is widespread and inhibitive...), but under certain conditions, leading power factor can be an issue, and when it is, harmonics and waveform (according to my techy friends at MeccAlte who manufacture good quality electronic and digital AVRs) can be attributed to the problem. Further evidence of how generators can be affected, under certain conditions are highlighted by Mr. Gary Olson, the Director of Power Systems Development at Cummins Power Generation in page two of his white paper, who I believe, is uniquely placed to offer an opinion on this subject.

This from his white paper attached to post No's 9 and 10:

'Over the past years, generator set manufacturers have evolved their equipment designs to include use of digital automatic voltage regulator (AVR) equipment, separate excitation systems, and PWM-type control architecture to enable the generator set to produce and stable output voltage and successfully operate non-linear loads.

At the same time, manufacturers of equipment that has non-linear load characteristics have begun to commonly employ filters to limit harmonic current distortion induced on the power supply. Capacitive elements are also applied in facilities to improve the power factor when operating on the utility source to avoid higher energy charges. While filters provide positive impacts on the overall power system, they can be very disruptive to generator operation.

The generator set AVR monitors generator output voltage and controls alternator field strength to maintain constant output voltage. Relatively low AVR output is required to maintain generator voltage at no load. In the figure shown, the no load exciter field current required is less than half the full load level.

Filter equipment is often sized for operation at the expected maximum load on the UPS or motor load. At light loads there may be excess filter capacitance, causing a leading power factor. Since rectifiers are commonly designed to ramp on from zero load to minimize load transients, leading power factor loads may be imposed on the system until inductive loads are added to the system or the load factor of the nonlinear load increases.

A utility supply simply absorbs the reactive power output because it is extremely large relative to the filter system and it has many loads that can consume this energy. With a generator set, however, the rising voltage from the leading power factor causes the voltage regulator to turn down and reduce alternator field strength. If the AVR turns all the way off it looses control of system voltage, which can result in sudden large increases in system voltage. The increase in voltage can result in damage to loads, or can cause the loads to fail to operate on the generator set.

A UPS is designed to recognize high voltage as an abnormal and undesirable condition, so it can immediately switch off its rectifier. When it does that, the high voltage condition is immediately relieved (because the filter is disconnected from the generator set) and voltage returns to normal. To the observer, the generator will seem to be unable to pick up the system loads.'

Taken from 'Impact of leading power factor loads on synchronous alternators' by Mr. Gary Olson, the Director of Power Systems Development at Cummins Power Generation.

To summarize, a UPS system may operate without fault, appear not to operate and/or potentially cause problems with the operation of AVRs, but the 'real life' default, in my experience, is that this is really something of a non-issue.

Genset

[robm]

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?

having spoke to op turns out i had a first generation genny (old one) he seems to be well informed on all types off genny .....

thanks for help and info .....

[InterestedObserver]

2 x 875KVA 4 pole 50hz generators. Auto start on mains failure or undervoltage.

Generators connected to an ATS. Generators run in parallel (auto synronisation)

One of the areas supplied was the IT centre and it was equipped with a 20KVA

3 phase UPS which was designed to carry a fixed load for 30mins.

System PF was generally between 0.85 an 0.9

And there was never any problem with harmonics or voltage stability.

A 20KVA UPS on 2 x 875KVA generators is not a significant part of the total load, hardly worth mentioning as indicated by the system power factor. Any harmonics (waveform distortion) associated with the UPS would be completely overwhelmed by the other generator loads, hence the stable AVR operation.

[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?

Hi Naam,

I should have given you the formula for calculating amps from Kw when using a 3 phase generator, also, Kipors rating calculation for this machine, is based on a voltage of 230/400v, I should have converted that (as the avr is adjustable to 220/ 380) to reflect the correct calculation for Thailand... my apologies.

no need for apologies i didn't know that there is a difference in calculation.

[InterestedObserver]

[(400 volts)(24.5 amps)(0.8 power factor)(1.732 constant)]/1000 = 13.6 KW 3-phase power

[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.

Hi Naam,

These are the specs for the KDE20SS3 I mentioned in my earlier post to you.

KDE20SS3 – 17Kva Rated as a PRP Generator (Prime Power).

• 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).
  
• 17Kva (13.6Kw) as a PRP set and 20Kva (16Kw) as an LRP set. This set will easily power a large home, with AC's, and numerous electronic appliances.
  
• This is a Super Silent Generator set, enclosed in a well constructed soundproof canopy;The unique air handling system reduces the bulk of the engine noise. A double muffler and the use of high quality acoustic absorbing material result in maximum silencing. Unit operates at 51db/7m on a full load, very quiet.
  
• Electronic AVR voltage regulation.
  
• Brushless, 3-phase, self exciting, 4 pole alternator.
  
• In-line 4 cylinder, four-stroke, water cooled, direct injection diesel engine.
  
• KDE20SS3 operates at 1500rpm, producing three phase, 400v p-p @ 50Hz, and delivering approx 24.5 amps per phase of useable power as a PRP set and 28.9 amps per phase of useable power as an LRP set.
  
• Electric start, the unit also features a digital control panel with a remote start facility and additional features such as a periodical exerciser function.
  
• Unit features 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.
  
• 12 hours runtime when loaded and fully fuelled.
  
• Access points for fuelling, adding coolant etc are conveniently located on the exterior of the generator canopy. Taps to drain and refill engine oil are conveniently located along the skid for ease of maintenance.
  
• Unit must be grounded.
  
• 12 months warranty.
  

Price including VAT from distributor;

KDE20SS3 – 220,000 Thb

These generators can also be seen on my website at http://www.generatorsolutions.org/#/need-a...ator/4534282010

[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,

Please disregard, the information I gave you in an earlier post regarding recalculation of the KDE20SS3 amp rating for use in Thailand.

The rated amperage per phase for this set is 24.5amps @ 400v p-p, 50hz. I have been reminded by InterestedObserver (who I would like to thank for keeping me on my toes), that my amended calculation (using 220v and thereby increasing the amperage rating) can only be made if these alternators are dual rated (a dual rated aternator is wound with copper wire of a sufficient thickness and thermal insulation of a sufficient grade to withstand the increased temperature associated with increased amperage for dual voltage use. Amp ratings will normally be stamped on a data plate for available voltage configurations). The alternators I work with on a daily basis are indeed dual rated, but 3 phase Kipor alternator on the KDE20SS3 is rated to produce a maximum 24.5amps per phase at 230/400v period.

I have made a point of stressing the need to size alternators correctly (suggesting maximum load requirement at 70-80% of the alternators maximum load rating) precisely to avoid the potential for thermal damage to the alternator windings, so I would like to apologize for dropping a boll*ck on this one.

It is still possible to adjust the AVR to produce 220/380v for use in Thailand, but the rating of 24.5amps per phase will remain the maximum rated output when used as an LRP set and 19.5amps per phase as a PRP set.

Apologies for the confusion and happy to see that these posts are actually being read and scrutinized... I'll try not to let it happen again...

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?

[/color]

I should have given you the formula for calculating amps from Kw when using a 3 phase generator, also, Kipors rating calculation for this machine, is based on a voltage of 230/400v, I should have converted that (as the avr is adjustable to 220/ 380) to reflect the correct calculation for Thailand... my apologies.

no need for apologies i didn't know that there is a difference in calculation.

here's the formula provided by genset:

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

[Naam]

I am waiting for the distributor to get back to me with the latest price, I will add it to the post when I receive it and PM you to let you know.

can't you shoot from the hip?

weighs 790Kg

big crane needed. distance from roadside to projected installation site straight 15-16m plus must be lifted over servants quarter 4.5m high

Electric start, the unit also features a digital control panel with a remote start facility and additional features such as a periodical exerciser function.

remote start facility a must. what's an "exerciser function"?

Unit features 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.

automatic transfer (unfortunately) not possible as most probably too many consumers online when brown out or complete black out happens. have to re-evaluate my situation as rewiring of mandatory consumers to one phase should make it possible to use automatic transfer. anything wrong in my thinking?

additional information: brown outs of one or two phases happen quite often. i spent a fortune on replacing burned pump and compressor relays till i had a gadget installed which shuts off a phase completely if voltage drops below a certain value (value can be adjusted, settings are presently at 200 volts).

[Isan Farang]

I am in the process of calculating all my equipment i have to opperate a large selection of fish tanks, all the pumps and various items are marked in w, i have a chiller that has the following info Electrical current 4.2A, Power 1 1/4 HP. Can someone please inform me what this amounts to in W.

[tjo o tjim]

Genset-- I know the Cummins document very well; the challenge is finding reliable capability curves for any system. Specific to Cummins, even their MW class machines choke on a few hundred kVAR... and don't get me started on their dam_n MCRS system.

But specific to readers needs, computers and UPS systems do create enough of a leading power factor to cause a problem for a generator designed for 0.8PF lagging loads. Inverter-based AC systems don't help things either.

So, my question remains-- do you have a capability curve for the generators you are representing?

[InterestedObserver]

I am in the process of calculating all my equipment i have to opperate a large selection of fish tanks, all the pumps and various items are marked in w, i have a chiller that has the following info Electrical current 4.2A, Power 1 1/4 HP. Can someone please inform me what this amounts to in W.

Electrical Horsepower: 1HP = 746 Watts, so 1.25HP = 933 Watts. That's the best answer you can get without getting into all sorts of electrical stuff such as motor efficiency, power factor, rated voltage etc.

[bilinlos]

Genset,

I plan to use a combination of solar power and a genset. What is your opinion of this. Also I have considered using propane in my home and had thought with a larger propane tank, I could power a genset with it also. What do you know of Propane powered gensets. I realize there could be a conversion from Gas to Propane but is that common in Thailand?

[InterestedObserver]

Genset-- I know the Cummins document very well; the challenge is finding reliable capability curves for any system. Specific to Cummins, even their MW class machines choke on a few hundred kVAR...

Do you mean they choke on a few hundred kVAR with a leading PF? The capacity curves will indicate the limit, but the reactive power control system (AVR or kVAR/PF controller) is another subject. Knowledgeable power system professionals avoid leading PFs like the plague.

[genset]

Genset-- I know the Cummins document very well; the challenge is finding reliable capability curves for any system. Specific to Cummins, even their MW class machines choke on a few hundred kVAR... and don't get me started on their dam_n MCRS system.

But specific to readers needs, computers and UPS systems do create enough of a leading power factor to cause a problem for a generator designed for 0.8PF lagging loads. Inverter-based AC systems don't help things either.

So, my question remains-- do you have a capability curve for the generators you are representing?

I dont have the data/graphs at hand, but I will endeavour to get copies of alternator specs over the next few days and post them when I do.

Genset

[genset]

Genset,

I plan to use a combination of solar power and a genset. What is your opinion of this. Also I have considered using propane in my home and had thought with a larger propane tank, I could power a genset with it also. What do you know of Propane powered gensets. I realize there could be a conversion from Gas to Propane but is that common in Thailand?

Hi Bilinlos,

This seems to be a popular idea, I have received a number of similar enquiries through my website and if you like I can provide you with the email address of a guy who works on hybrid photovoltaic systems. Personally, I have no knowledge of solar power systems, so I can't offer you an opinion I'm afraid.

Again, my knowledge of propane powered gensets is wafer thin. I work exclusively with diesel generators and the odd petrol genny thrown in for good measure. I did visit a pig farm in Thailand recently (with a Thai tech fitting a ComAp unit) and saw an interesting system... they collected and pressurized the methane gas pig emissions from the pig houses and ran the generator from it... amazing.

In answer to the second part of your question, I believe there are generators running on propane in Thailand, but I have no knowledge of their operation or cost I'm afraid. If you absolutely must go the propane route, I can certainly make some enquiries on your behalf, drop me a line @ [email protected] if you wish.

Genset

[genset]

I am in the process of calculating all my equipment i have to opperate a large selection of fish tanks, all the pumps and various items are marked in w, i have a chiller that has the following info Electrical current 4.2A, Power 1 1/4 HP. Can someone please inform me what this amounts to in W.

Electrical Horsepower: 1HP = 746 Watts, so 1.25HP = 933 Watts. That's the best answer you can get without getting into all sorts of electrical stuff such as motor efficiency, power factor, rated voltage etc.

Hi Isanfarang,

Dont forget that the calculation posted by InterestedObserver, based on your nameplate data is the running watts. Multiply this by 3 (an approximation) and you will have a rough estimate (for the purposes of calculating your load requirement) of your starting watts.

Genset

[genset]

I am waiting for the distributor to get back to me with the latest price, I will add it to the post when I receive it and PM you to let you know.

can't you shoot from the hip?

I can tell you that the KDE20SS3 is more costly than the KDE16SS, but not by how much until I speak to the distributor I'm afraid, if you could give me a couple of days I will post the details for you. Thanks for your patience.

weighs 790Kg

big crane needed. distance from roadside to projected installation site straight 15-16m plus must be lifted over servants quarter 4.5m high

Yes, it's a hefty weight. These sets are normally delivered on a flat bed with hydraulic lifting equipment to position it. To place it 15m from the delivery vehicle and over your servants quarters will certainly require the use of a crane, make sure you find a competent operator...!

Electric start, the unit also features a digital control panel with a remote start facility and additional features such as a periodical exerciser function.

remote start facility a must. what's an "exerciser function"?

This is a function of an electronic control unit which can be set to periodically start and stop the generator. For example; you could set the exerciser function to automatically start the set once a week, on a saturday morning at 10:00 and to run for 30 minutes, or every fortnight, or once a month as you see fit.

A standby generator should be able to go from a cold start to fully operational and on load in less than a minute. This can place a lot of strain on engine parts; regular exercising of the generator, circulates fluids, keeps engine parts lubricated and moves diesel fuel through the system, allowing it to be used before it begins to deteriorate; all of which increase the reliability of engine starting. Having said this, long periods of generator exercising with 'no load' should be avoided, it is far better to let the generator run on load for the period of exercising by switching your load from mains to generator during the exercise period.

Unit features 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.

automatic transfer (unfortunately) not possible as most probably too many consumers online when brown out or complete black out happens. have to re-evaluate my situation as rewiring of mandatory consumers to one phase should make it possible to use automatic transfer. anything wrong in my thinking?

Are you saying that the load would exceed the maximum rated output of the generator, if an automatic transfer between mains and generator supplies took place, given your current distribution configuration, as we discussed in your earlier post? If this is the case, then I do understand why you feel an automatic transfer switch would not work for you.

As for running all your mandatory customers from one phase... No, unfortunately that would present a problem. When operating a 3 phase generator, the load must be balanced, or distributed as evenly as possible over the three phases, you cannot load one phase to the gills and have no load on the other two phases.

additional information: brown outs of one or two phases happen quite often. i spent a fortune on replacing burned pump and compressor relays till i had a gadget installed which shuts off a phase completely if voltage drops below a certain value (value can be adjusted, settings are presently at 200 volts).

[david96]

The Effects of UPS systems on a Generator.

The designer shall ensure that the generator is suitable for the operation with the UPS load.

When the UPS rectifier load is more than 50% of the total load connected on a generator,

the following special measures shall be considered to ensure stable and reliable operation

of the generator.

1. Using a 3 phase AVR.

2. Using permanent magnet field excitation.

3. Using an electronic governor.

4. Oversizing the alternator compared with the kW rating required.

5. Specifying the UPS with filtering to limit the amount of harmonic distortion, where possible.

Where the UPS equipment represent a significant load on the generator, that is at or close to its max. output, overloading shall be prevented by inhibiting or limiting the battery charging function of the UPS when connected to the generator supply, where possible.

Autostart Generators.

Auto start generators connected to a switchboard though an ATS sense the loss of voltage,loss of phase or phase imbalance % by the use of a phase failure relay, with a time delay in secs so as to avoid transient events. The setting is usually 5 secs but in some critical circumstances may be less. There is usually an adjustable time delay after power has been restored before the ATS changes over to mains power. There is a run on time usually 20 mins and then the generator will shut down, however if there is a power failure in this time the ATS will transfer load to the genset and it will continue running.

The phase failure relays, one for mains supply and one for generator supply are generally located in the ATS switch.

Generator selection.

The generator supplier needs to know the type and size of proposed load in order to recommend a generator that is suitable. And if you are going to use manual start with manual changeover switch or auto start with an ATS.

Remember you have the cost of the genset and then you have the cost of installing, testing and commissioning into service.

Good design will eliminate a lot of potential problems.

[InterestedObserver]

david96, Re: The Effects of UPS systems on a Generator. Nowhere do I see a reference to leading power factor caused by UPS systems and other non-linear loads. Are you trying to say that the problem does not exist or that it should just be ignored whenever encountered? What do you do when sent to install a standby generator at an existing data center where the power quality (PQ) analysis shows significant harmonics present and at times a leading power factor?

[david96]

david96, Re: The Effects of UPS systems on a Generator. Nowhere do I see a reference to leading power factor caused by UPS systems and other non-linear loads. Are you trying to say that the problem does not exist or that it should just be ignored whenever encountered? What do you do when sent to install a standby generator at an existing data center where the power quality (PQ) analysis shows significant harmonics present and at times a leading power factor?

The designer shall ensure that the generator is suitable for the operation with the UPS load.

If you read this line it means that the designer of the system must take into consideration the UPS that is to be connected. The designer has to comply with the required standards in this case:

AS3000/2007 Wiring rules

AS3010. Electrical Installations - Supply by generator set.

AS62040. Uninteruptible Power Systems (UPS).

These are only some of the standards. The Standards set the requirements regarding a leading PF and the effect of harmonics.

The designer will be usually be a qualified Electrical Engineer. The Installer will be a licensed Electrical contractor.

[tjo o tjim]

david96, Re: The Effects of UPS systems on a Generator. Nowhere do I see a reference to leading power factor caused by UPS systems and other non-linear loads. Are you trying to say that the problem does not exist or that it should just be ignored whenever encountered? What do you do when sent to install a standby generator at an existing data center where the power quality (PQ) analysis shows significant harmonics present and at times a leading power factor?

The biggest thing that you have to do for generator compatibility with UPS rectifier is ensure that you disengage harmonic filters when on generator. Unfortunately, many of the computer power supplies themselves have leading power factor (-0.97 is becoming typical from the facilities we work in), which makes for a problem when the UPS goes to bypass. We are adding line inductors to a number of sites to fix things, but it is an awful solution.

Harmonics though (at a data center scale) have pretty much been eliminated as a problem in all the sites we work in.

[Naam]

Are you saying that the load would exceed the maximum rated output of the generator, if an automatic transfer between mains and generator supplies took place, given your current distribution configuration, as we discussed in your earlier post? If this is the case, then I do understand why you feel an automatic transfer switch would not work for you.

because the sum of all consumers normally running (plus the potential ones on timers or on demand such as pool pump, deep well, waterfall, pond filter) would exceed 13.6 kW. only the dedicated solution (max 10 kW) wired to one specific phase, combined with a single-phase generator would make an autostart/transfer possible.

As for running all your mandatory customers from one phase... No, unfortunately that would present a problem. When operating a 3 phase generator, the load must be balanced, or distributed as evenly as possible over the three phases, you cannot load one phase to the gills and have no load on the other two phases.

i meant of course dropping the three-phase idea and go for a single-phase unit. that would make an autostart/transfer possible.

[InterestedObserver]

The biggest thing that you have to do for generator compatibility with UPS rectifier is ensure that you disengage harmonic filters when on generator. Unfortunately, many of the computer power supplies themselves have leading power factor (-0.97 is becoming typical from the facilities we work in), which makes for a problem when the UPS goes to bypass. We are adding line inductors to a number of sites to fix things, but it is an awful solution.

Nicely said, all those nasty switched mode power supplies with PFC, thus typically leading power factors, load up the standby generator.

[genset]

I am waiting for the distributor to get back to me with the latest price, I will add it to the post when I receive it and PM you to let you know.

can't you shoot from the hip?

Hi Naam,

I have added the price for the KDE20SS3 in post No 42.

Genset

[genset]

Genset-- I know the Cummins document very well; the challenge is finding reliable capability curves for any system. Specific to Cummins, even their MW class machines choke on a few hundred kVAR... and don't get me started on their dam_n MCRS system.

But specific to readers needs, computers and UPS systems do create enough of a leading power factor to cause a problem for a generator designed for 0.8PF lagging loads. Inverter-based AC systems don't help things either.

So, my question remains-- do you have a capability curve for the generators you are representing?

Hi tjo o tjim,

My apologies for the delay in responding to your post, I have been in touch with an agent at Kipor and he has informed me that he doesn't have the capability curve graph/data you requested, available to him.

Whether this specific data was required to be submitted by Kipor during CE conformity test verification (EN12601:2001 Low Voltage Directive 2006/95/EEC) or not is a question I can't answer; unfortunately I don't know enough about the verification process to tell you whether it is a prerequisite to certification; but these generators do conform to the requirements of the specific EEC/CE directives.

I think I messed with the agents head a little to be honest. I ran him ragged looking for info and I'm not entirely sure he knew what he was supposed to be looking for, (his primary role is simply to take sales orders). He was most apologetic and insisted that this was the first time he had ever been asked for this type of specific information… I can't say I'm surprised at his response, I've yet to be approached by a customer asking this kind of question...in all the years I've been working with generators, most of my customers are happy if they can figure out how to turn it on and fill it with diesel; hardly surprising really, the effects of leading power factor on a generator is of minor concern to most farmers.

Having said that, I appreciate your reason for posing the question and I have asked the agent to forward my email address to a member of their technical team, who may be in a better position to cough something up. If I make any headway I'll be sure to let you know.

On your comments regarding Cummins generators; generally Cummins feature Stamford aternators, Stamford as you probably know, is a large, reputable alternator manufacturer. If you are disappointed with the performance of Stamford alternators in respect to leading power factor, the chances of a Kipor alternator fairing any better are fairly slim I'd say.

Where non-linear loads are present, and no other option exists, I would normally advise a customer to consider purchasing a generator with an increased Kw rating (beyond their calculated load requirement), as I believe (and again, my techy mates at Mecc Alte advised me on this), that it will diminish the effects somewhat.

Genset.

[genset]

The Effects of UPS systems on a Generator.

The designer shall ensure that the generator is suitable for the operation with the UPS load.

When the UPS rectifier load is more than 50% of the total load connected on a generator,

the following special measures shall be considered to ensure stable and reliable operation

of the generator.

1. Using a 3 phase AVR.

2. Using permanent magnet field excitation.

3. Using an electronic governor.

4. Oversizing the alternator compared with the kW rating required.

5. Specifying the UPS with filtering to limit the amount of harmonic distortion, where possible.

Where the UPS equipment represent a significant load on the generator, that is at or close to its max. output, overloading shall be prevented by inhibiting or limiting the battery charging function of the UPS when connected to the generator supply, where possible.

Hi David96,

Since the inception of this thread, you seem to have taken a position (based on your earlier posts, No36 for example) contrary to the assertion that under certain conditions (when running on generator power), UPS systems may not operate as designed or cause problems with generator operation.

This is your prerogative and your opinion is welcome, of course, but if you choose to continue discussing this particular aspect of generator use, then I would be grateful if you ensure that the content of your post, (when that content is drawn from other sources) is a complete and accurate reflection, of the portion of the document from which it is copied. Only then can your post be read in proper context.

It would also be helpful if you would credit the source of your text and perhaps offer a link, so that readers may read the document in full, should they so wish.

Unfortunately, you have chosen to omit a paragraph from your post, which is present in the original document and contains the premise for the entire sub-section in which it appears, it also places the 5 points you cite in context. The lack of context appears to have been the reason for InterestedObservers post No66, in your response you have referred to one line from the missing paragraph by citing Australian Standard 'AS62040. Uninteruptible Power Systems' (UPS); please lets not play games here... I had hoped this thread would be a source of good information for people considering the purchase of a generator.

If you read this line it means that the designer of the system must take into consideration the UPS that is to be connected.

The designer has to comply with the required standards in this case:

AS3000/2007 Wiring rules

AS3010. Electrical Installations - Supply by generator set.

AS62040. Uninteruptible Power Systems (UPS).

These are only some of the standards. The Standards set the requirements regarding a leading PF and the effect of harmonics.

You have mentioned that these are only 'some' of the standards, but have again, chosen not to mention two others, which would appear to have a direct bearing on the issue in question, and which appear in the omitted paragraph, namely... 'AS2279 Disturbances in Mains Supply Network and AS/NZS 61000 Electromagnetic Capability (EMC) '. I can only conclude that you have omitted this paragraph as it runs counter to your original stance on this issue.

I have contacted you twice and politely requested that you consider editing your post and placing it into context for readers of this thread. Despite responding that it was not your intention to mislead, you have decided not to do so, and I will therefore place your words in context myself.

The following is an accurate reflection of the section in question from an Australian Defence Dept technical/policy document http://www.defence.gov.au/IM/policy/techni...equirements.pdf and should be compared with your original post to better place your comments in context, the missing paragraph is No30 below. The sub-section containing the text appears on page 8 of the PDF document.

The Effect of UPS on the Generator

30. The controlled rectifiers of UPS systems can be a major source of harmonics which can produce distortions of the voltage and current waveforms and may have a detrimental effect on a variety of electrical equipment both upstream and downstream of the UPS system. The designer shall ensure compliance with relevant Australian Standards AS2279 Disturbances in Mains Supply Network, AS/NZS 61000 Electromagnetic Capability (EMC) and AS 62040 Uninterrupible Power Systems (UPS) to minimise the effects of harmonics on electrical equipment.

31. The designer shall ensure that the LEG is suitable for operation with the intended UPS load. When the UPS rectifier load is more than about 50% of the total load connected on a generator, the following special measures shall be considered to ensure stable and reliable operation of the generator:

a. Using a three phase voltage regulator;

b. Using permanent magnet field excitation

c. Using an electronic governor;

d. Oversizing the alternator compared to the kW rating required; and

e. Specifying the UPS with filtering or 12 pulse rectifiers to limit the amount of

harmonic distortion, where possible.

32. When the UPS represents a significant load on a generator that is operating at or close to its maximum output, overloading shall be prevented by inhibiting or limiting the battery charging function of the UPS when connected to the generator supply, where possible.

One of the aims of this thread is to deliver accurate and helpful information for anybody taking the time to read through it. I would be most grateful if posters (especially those with an engineering or electrical background), would make an effort to avoid posts which are out of context or may serve to mislead a reader, even if that is not your intention.

Genset

[Marvo]

Hi Genset et al, thanks for a great informative thread. My situation is that I will soon be looking for a Silent PRP generator (12kVa -ish single phase) as electricity is 800m away from my plot. I still have to calculate if a generator is a viable alternative to paying out about 700,000 baht to have the grid delivered to my door as 220v. Comments welcome.

My issue is how many litres of diesel per hour (rather baht per hour) will it burn? That 12 kVa will be enough to start up the well pump, and a small a/c unit if switched on at he same time, but for most of the time I'll only be using a TV, a computer, fridge freezer, a couple of fans and some lights at night time. The generator for all this time will be running at what? 50%, 70%? burning diesel and baht like crazy to deliver 1-2 Kw max. What's my solution?

Thanks,

Marvo.