3 Phase Power

[JeffreyMcCollum]

Where I came from, 3 phase power was limited to industrial, factory, as well as some farm use..

Homes were never 3 phase. Why is it used here in some cases ?

Over the years I have had several homes here in Thailand and all were single phase.

So why is this one 3 phase when there is no more anything than the other homes ?

nstead of a simple breaker box, I have the box, what appears to be a relay box, and 1 very large box with colored lights. and switches on it ? What is all this complexity for ?

Can this be converted to single phase ?

I have a large single phase back up generator. Single phase, How hard would this be to add on as a back up when the power fails ? The unit is the size of a car. diesel 4 cyl and 69 kw

Please help me understand this better

[InterestedObserver]

1. Three-phase for residential homes is used when the single-phase supply is undersized, overloaded and tends to suffer low voltage as a result..

2. The complex relay box is probably undervoltage and phase failure protection.

3. A single-phase backup generator with transfer switch could be wired to provide power failure protection for the single-phase loads.

[Darrel]

We had 3-phase supply in Europe. It must have dated from the 60s. It was quite common in old farm buildings as electricity was often used for all space heating, water heating, welding, water pumps, milking cows and God knows what else etc. etc.

We never got round to having the meter put back to single phase, not least because some unknown previous owner of the building had had the meter rewired and the lead seal put back, and so one of the phases didnt make the counter go round.

To get single phase from a 3-phase supply, just use any of the 3 live wires plus the neutral as your pair. You are supposed to balance the load on the three phases but it never seemed to make any difference in our place.

I should add that it's best not to screw around with 3-phase if you dont know what you are doing as the 400V can kill.

Edited September 16, 2011 by Darrel

[cheeryble]

Can this be converted to single phase ?

I have a large single phase back up generator. Single phase, How hard would this be to add on as a back up when the power fails ? The unit is the size of a car. diesel 4 cyl and 69 kw

Please help me understand this better

Briefly....

3 phase is simply made up of three supplies which have the peak of their voltage curve 120degrees, one third of a cycle, out of step.

When you add all the phases you get a higher voltage than any of the single phases, and importantly for industry and efficient machinery, it's a smoother voltage delivery.

Highly unlikely you need it in your home, in fact it can be a pain in the arse, and you. Have already hinted why by asking about a backup generator.

Because you have a 3 phase house it is likely that you have 3 different circuits each running from a phase. So if u hook up the generator it will only run one circuit.

Better than nothing, yo can run the lighting or run lights from the. Power circuit and keep the freezer going, but not a perfect scenario.

Interested Observer was quite right, you likely have three phase because each phase was insufficient.

I would now check if there are more amps available on a single phase since your house was hooked up.

Cheeryble

[stgrhe]

A three-phase domestic installation has also other advantages provided the circuits have been properly done. 1) light-circuits can be put on a different phase than electrical motors so if the supply is unstable there will be no flickering; 2) In the event of a failure on one of the phases you would still at least have one fully function phase.

[katabeachbum]

Max one phase supply from PEA is 100Amp. In many areas limit is one phase 45Amp tho, and in some Moo Baans limit is 30Amp.

For some homes this is not sufficient, so next step is 3phase 4 wire, providing more power

[cheeryble]

Max one phase supply from PEA is 100Amp. In many areas limit is one phase 45Amp tho, and in some Moo Baans limit is 30Amp.

For some homes this is not sufficient, so next step is 3phase 4 wire, providing more power

We could of course try not living as if we're in the US with all that power burning away.........if I couldn't live with 30 or 40amps in a sub tropical country I'd think something was wrong.

[ding]

3 phase is more efficient. If you have a neutral -or groundED conductor- you have 120V off any one leg. This is done with a 3 phase DELTA transformer - (often a seperately derived system) - and you bond the center of one winding to ground. Pretty hairy when you throw the breaker handle that first time.

3 phase 4-wire is great. You may enjoy the odd bit of commercial equipment.

What is your supply? Volts, Amps, is there a Neutral/grounded conductor present?

For your genset, I suggest not interconnecting it. If you do, be sure to have a lock-out or an Auto Transfer Switch (ATS). Even a Manual Transfer Switch (MTS) works. Power company workers would definitely come see you if you backfed their distribution system. Just plug crap in when the juice cuts off, no worries.

Call a Thai sparky or two and pay them to check it out. It'd be fun.

...or just get a massage and don't think too mut

Edited September 17, 2011 by ding

[InterestedObserver]

3 phase is more efficient. If you have a neutral -or groundED conductor- you have 120V off any one leg. This is done with a 3 phase DELTA transformer - (often a seperately derived system) - and you bond the center of one winding to ground. Pretty hairy when you throw the breaker handle that first time.

3 phase 4-wire is great. You may enjoy the odd bit of commercial equipment.

What is your supply? Volts, Amps, is there a Neutral/grounded conductor present?

For your genset, I suggest not interconnecting it. If you do, be sure to have a lock-out or an Auto Transfer Switch (ATS). Even a Manual Transfer Switch (MTS) works. Power company workers would definitely come see you if you backfed their distribution system. Just plug crap in when the juice cuts off, no worries.

Call a Thai sparky or two and pay them to check it out. It'd be fun.

...or just get a massage and don't think too mut

I don't think so! A 3-phase delta transformer does not have a true neutral connection point (equal potential to all phases) and Thailand does not use "120V off any one leg". What you describe is known as high-leg delta; 3-phase, 4-wire is usually derived from a wye connected transformer with a true neutral point.

[cheeryble]

3 phase is more efficient. If you have a neutral -or groundED conductor-

....if?

you have 120V off any one leg.

Or 240v?

...or just get a massage and don't think too mut

....there we agree

[genset]

Hi Jeff,

Interested Observers initial post was quite succint and answered your original post very well. Additional posts have muddied the water a little, so returning to your original post once more, let me offer the following to supplement the answer given by Interested observer in post 2.

• In Thailand the single phase voltage is 220v @ 50hz - 3 phase voltage is 380v phase to phase and 220v phase to neutral again at 50hz - please ignore all other posts referring to voltage in this string, they are incorrect in respect to Thai utility supply.
• In addition to phase failure relays etc, where a 3 phase supply is presented in Thailand it is common to find a panel with lights, selector switches and gauges to allow you to monitor the voltage and amps (if CTs are in place) for each phase.
• If you have a proper 3 phase distribution board installed and regardless of 3 phase appliances, each of the single phase circuits in your home should be balanced over the 3 phase supply so that an equal load is placed on each phase.
• In respect to your generator, a 69Kw single phase alternator equates to approx 85Kva at 0.8 power factor, this will provide you with somewhere in the region of 380amps of usable single phase power, which is a substantial supply. Depending on the maximum load requirement of your home, there are a couple of ways you could integrate this generator as a stand by power supply, but whether connected to supply your DB or a sub-panel, it absolutely must be connected via a manual or automatic transfer switch (if manual it should be three position 'break before make' type and if automatic it should include both electrical and mechanical interlocks).

Genset.

Edited September 18, 2011 by genset

[Darrel]

In Thailand the single phase voltage is 220v @ 50hz - 3 phase voltage is 380v phase to phase and 220v phase to neutral again at 50hz

Sounds exactly like what we had in Europe.

We never had any sort of regulator or phase relay or boxes with flashing lights though. Just the 3 live wires + the neutral coming out of the meter, and these were split off onto regular single-phase circuits each with its own single-phase breaker. Of course our installation did date back several decades (probably about 50 years).

[JeffreyMcCollum]

Sorry, House chores, sore back and now backt o TV . . .

Hi Jeff,

Interested Observers initial post was quite succint and answered your original post very well. Additional posts have muddied the water a little, so returning to your original post once more, let me offer the following to supplement the answer given by Interested observer in post 2.

• In Thailand the single phase voltage is 220v @ 50hz - 3 phase voltage is 380v phase to phase and 220v phase to neutral again at 50hz - please ignore all other posts referring to voltage in this string, they are incorrect in respect to Thai utility supply.

With my volt tester at the outlets I get 223 or 224V

• In addition to phase failure relays etc, where a 3 phase supply is presented in Thailand it is common to find a panel with lights, selector switches and gauges to allow you to monitor the voltage and amps (if CTs are in place) for each phase.

Yes, 3 boxes by the back door. 1 looks like a traffic light with Green red and yellow lights

• If you have a proper 3 phase distribution board installed and regardless of 3 phase appliances, each of the single phase circuits in your home should be balanced over the 3 phase supply so that an equal load is placed on each phase.

I am the second owner of the home. It was this way when I got it. Once when changing the shower hot water, we tried to switch the breaker and noticed some things were just directly wired in with no breaker at all. A/C units just spliced into outlet circuts, etc... I have a small office and that was just on a single breaker, with A/C, outlets, and lights, so now that has a sub panal (single phase) and the up stairs is another sub panal single phase box with "Now proper" breakers for each A/C unit (3) and ho0t water (2) as well as outlets and lights. The down stairs remain on the original 3 phase set up, I guess

• In respect to your generator, a 69Kw single phase alternator equates to approx 85Kva at 0.8 power factor, this will provide you with somewhere in the region of 380amps of usable single phase power, which is a substantial supply. Depending on the maximum load requirement of your home, there are a couple of ways you could integrate this generator as a stand by power supply, but whether connected to supply your DB or a sub-panel, it absolutely must be connected via a manual or automatic transfer switch (if manual it should be three position 'break before make' type and if automatic it should include both electrical and mechanical interlocks).

Home has 6 A/C units, 2 4500W hot shower units, Cook top, Oven, Washing machine, a freezer, as well as the usuall lights and plugs. My wife has a health condition and has problems with the heat. We wanted a generator that could handle most things. And got this diesel unit at Home Pro. It is the size of a car, has a auto start up feature and swithch. Digiatal display etc... However for some reason they are having trouble hooking it up properly and at one point said I could only run lights or outlet or A/C. But with the size of it I thought it could do almost everything

Genset.

[InterestedObserver]

I am the second owner of the home. It was this way when I got it. Once when changing the shower hot water, we tried to switch the breaker and noticed some things were just directly wired in with no breaker at all. A/C units just spliced into outlet circuts, etc... I have a small office and that was just on a single breaker, with A/C, outlets, and lights, so now that has a sub panal (single phase) and the up stairs is another sub panal single phase box with "Now proper" breakers for each A/C unit (3) and ho0t water (2) as well as outlets and lights. The down stairs remain on the original 3 phase set up, I guess

• In respect to your generator, a 69Kw single phase alternator equates to approx 85Kva at 0.8 power factor, this will provide you with somewhere in the region of 380amps of usable single phase power, which is a substantial supply. Depending on the maximum load requirement of your home, there are a couple of ways you could integrate this generator as a stand by power supply, but whether connected to supply your DB or a sub-panel, it absolutely must be connected via a manual or automatic transfer switch (if manual it should be three position 'break before make' type and if automatic it should include both electrical and mechanical interlocks).

Home has 6 A/C units, 2 4500W hot shower units, Cook top, Oven, Washing machine, a freezer, as well as the usuall lights and plugs. My wife has a health condition and has problems with the heat. We wanted a generator that could handle most things. And got this diesel unit at Home Pro. It is the size of a car, has a auto start up feature and swithch. Digiatal display etc... However for some reason they are having trouble hooking it up properly and at one point said I could only run lights or outlet or A/C. But with the size of it I thought it could do almost everything.

Your 69kW generator is plenty big enough to power the entire house. You just need a clever, knowledgeable electrician and a 4-pole transfer switch for the mains. The household distribution system is another subject altogether and you may need to rebalance the phases.

[electau]

Individual residential electrical installations do not generally require a 3 phase supply.

Multi unit blocks will have a 3 phase supply to the main switchboard and single phase to each unit, balanced as far as practicably accross the three phases and neutral.

　

Edited September 19, 2011 by electau

[Naam]

Individual residential electrical installations do not generally require a 3 phase supply.

Multi unit blocks will have a 3 phase supply to the main switchboard and single phase to each unit, balanced as far as practicably accross the three phases and neutral.

　

that depends on the individual perspective and demand. for sure i appreciate my 3-phase supply on which i insisted because in case one phase is gone or a voltage down brown-out occurs i still can run two thirds of my aircon units (which are spread over the three phases) and enjoy a cool environment in most parts of my home.

[stgrhe]

Individual residential electrical installations do not generally require a 3 phase supply.

Multi unit blocks will have a 3 phase supply to the main switchboard and single phase to each unit, balanced as far as practicably accross the three phases and neutral.

　

that depends on the individual perspective and demand. for sure i appreciate my 3-phase supply on which i insisted because in case one phase is gone or a voltage down brown-out occurs i still can run two thirds of my aircon units (which are spread over the three phases) and enjoy a cool environment in most parts of my home.

That was also one of my points, and we had in fact a fuse blown on the HV side of the transformer last week, but could still cook food, keep the fridge cool and have the water pump operating until PEA came and replaced the blown fuse.

[katabeachbum]

Max one phase supply from PEA is 100Amp. In many areas limit is one phase 45Amp tho, and in some Moo Baans limit is 30Amp.

For some homes this is not sufficient, so next step is 3phase 4 wire, providing more power

We could of course try not living as if we're in the US with all that power burning away.........if I couldn't live with 30 or 40amps in a sub tropical country I'd think something was wrong.

30-40 amp is not sufficient to run deep well pump, supply pumps, pool pumps, fridge/freezer, washingmachine, dishwasher, hotwater and electric gate, and none of these have nothing to do with US powerconsumption but do affect peak consumption

in my 7 bedroom/7 bathroom poolvilla we average 4.500 baht/month in electric supply, but need a one phase 100Amp to cover peaks

[genset]

Sorry, House chores, sore back and now backt o TV . . .

• In respect to your generator, a 69Kw single phase alternator equates to approx 85Kva at 0.8 power factor, this will provide you with somewhere in the region of 380amps of usable single phase power, which is a substantial supply. Depending on the maximum load requirement of your home, there are a couple of ways you could integrate this generator as a stand by power supply, but whether connected to supply your DB or a sub-panel, it absolutely must be connected via a manual or automatic transfer switch (if manual it should be three position 'break before make' type and if automatic it should include both electrical and mechanical interlocks).

Home has 6 A/C units, 2 4500W hot shower units, Cook top, Oven, Washing machine, a freezer, as well as the usuall lights and plugs. My wife has a health condition and has problems with the heat. We wanted a generator that could handle most things. And got this diesel unit at Home Pro. It is the size of a car, has a auto start up feature and swithch. Digiatal display etc... However for some reason they are having trouble hooking it up properly and at one point said I could only run lights or outlet or A/C. But with the size of it I thought it could do almost everything

Genset.

Hi Jeff,

Unfortunately this is a common story. GIven the size of your generator, it will undoubtedly supply most if not all of the single phase circuits in your home, however, depending on the current state of your domestic wiring/distribution boards, it may require a little inspired design but it should be quite possible to achieve.

I have recently been in communication with a chap in Hua Hin who purchased a generator and had it installed in February this year. The company who installed it (I wont name names here...) have been back numerous times in an effort to get him up and running, but as of the beginning of September, it was as much use as a chocolate fire guard... that's 7 months of zero operation for what was a significant investment for this chap. Happy to report that I managed to solve the problem after a 2 hour visit although there are a couple of serious (in my opinon) flaws with the transfer switch installation, I have advised him in respect to required corrective action and he is going to make those changes asp.

Connecting a standby power supply such as a generator to your distribution board via a transfer switch is a fairly straightforward operation, however... it should be done by somebody familiar with Automatic Mains Failure operation in the case of an auto transfer switch and at least a modicum of common sense and electrical knowledge if a manual transfer switch (always use a three position 'break before make' type)... If in doubt... ask please folks, there are a few very knowledgable long term forum members in this specific sub-forum who are more than willing to offer good solid advice.

Genset

Edited September 19, 2011 by genset

[lockman]

Well on the advice of my builder and the electric company I had 3 phase installed for our house when built. That has been a huge benefit as we are out in the sticks and power per phase is limited as stated above. I do have 2 3 phase AC units as they are much cheaper to run vs 4 single phase units. The main benefit is often a phase goes out. The entire village has no power except for us as we still have 2 phases, and once only 1, but that was sufficient for the refrigerator and freezer. I also have a 7kw generator for when all goes out to run the refer & freezer. I will get that hard-wired into a receptacle and a transfer switch for the well pump. I'd keep the 3 phase myself.

[cheeryble]

Max one phase supply from PEA is 100Amp. In many areas limit is one phase 45Amp tho, and in some Moo Baans limit is 30Amp.

For some homes this is not sufficient, so next step is 3phase 4 wire, providing more power

We could of course try not living as if we're in the US with all that power burning away.........if I couldn't live with 30 or 40amps in a sub tropical country I'd think something was wrong.

30-40 amp is not sufficient to run deep well pump, supply pumps, pool pumps, fridge/freezer, washingmachine, dishwasher, hotwater and electric gate, and none of these have nothing to do with US powerconsumption but do affect peak consumption

Jeez you need your own power station. But wait. Isn't it plenty? You just don't need to run them all at the same time....

in my 7 bedroom/7 bathroom poolvilla we average 4.500 baht/month in electric supply, but need a one phase 100Amp to cover peaks

Ah I see......

You sleep in all those rooms one by one?

[electau]

Generally a supply authority will approve a 3 phase supply on the following.

1. Type of consumer. Residential. Commercial etc.

2. Load and maximum demand of consumer.

3. Type of electrical load. eg 3 phase motors.

4. Where single phase supply may cause undue voltage drop and affect other consumers. eg rural areas.

Loss of supply on one phase is not a reason for connecting a 3 phase 4 wire supply. Loss of a HV fuse will cause one phase to fall to 220/1.414 volts. to neutral.

[InterestedObserver]

Generally a supply authority will approve a 3 phase supply on the following.

1. Type of consumer. Residential. Commercial etc.

2. Load and maximum demand of consumer.

3. Type of electrical load. eg 3 phase motors.

4. Where single phase supply may cause undue voltage drop and affect other consumers. eg rural areas.

Loss of supply on one phase is not a reason for connecting a 3 phase 4 wire supply. Loss of a HV fuse will cause one phase to fall to 220/1.414 volts. to neutral.

With a typical Delta-Wye residential transformer, the loss of a HV primary fuse will cause low voltage on two secondary phases.

[electau]

Generally a supply authority will approve a 3 phase supply on the following.

1. Type of consumer. Residential. Commercial etc.

2. Load and maximum demand of consumer.

3. Type of electrical load. eg 3 phase motors.

4. Where single phase supply may cause undue voltage drop and affect other consumers. eg rural areas.

Loss of supply on one phase is not a reason for connecting a 3 phase 4 wire supply. Loss of a HV fuse will cause one phase to fall to 220/1.414 volts. to neutral.

With a typical Delta-Wye residential transformer, the loss of a HV primary fuse will cause low voltage on two secondary phases.

With a delta HV and star LV when there is loss of one HV phase the voltage on the LV will be,

LV eg. A phase to neutral 220V

B phase to neutral 220V

C phase to neutral 155V. ie 220/1.414.

A phase to B phase 380V.

B phase to C phase 0 volts.

C phase to A phase 0 volts.

Two phases to neutral are still available to maintain a limited supply.

[stgrhe]

When we recently had a fuse blown on the transformer's HV side, one phase was fully functioning providing 220V (in my case the R-phase). The voltage on the S-phase was just 100V + something, while the T-phase was "dead". Hence, in reality we had only one functioning phase but it was better than having none as we could keep some vital appliances (fridge / freezer) running.

[katabeachbum]

sorry, offtopic, but last night we had more than 300 Volt in our one phase supply for a few minutes. Today my fridge compressor doesnt work. Anyone tryed to complain to PEA when this happens, or is it just a waist of time?

correction, reading was past Voltmeters 250Volt max, so unknown Voltage above 250Volt

Edited September 21, 2011 by katabeachbum
correction

[Naam]

katabeachbum, on 2011-09-19 12:49:41, said:

30-40 amp is not sufficient to run deep well pump, supply pumps, pool pumps, fridge/freezer, washingmachine, dishwasher, hotwater and electric gate, and none of these have nothing to do with US powerconsumption but do affect peak consumption

in my 7 bedroom/7 bathroom poolvilla we average 4.500 baht/month in electric supply, but need a one phase 100Amp to cover peaks

cheeryble, Yesterday, 02:10 , bitched:

Ah I see......

You sleep in all those rooms one by one?

because he won't understand that some people have all areas of their homes airconditioned whether they sleep or are awake. it must also be hard for Cheeryble to comprehend that my monthly electricity bill during the hot season april-sept always exceeds 12,000 baht although my wife and my[not so]humble self sleep in one bedroom inspite of my snoring.

[InterestedObserver]

With a typical Delta-Wye residential transformer, the loss of a HV primary fuse will cause low voltage on two secondary phases.

With a delta HV and star LV when there is loss of one HV phase the voltage on the LV will be,

LV eg. A phase to neutral 220V

B phase to neutral 220V

C phase to neutral 155V. ie 220/1.414.

A phase to B phase 380V.

B phase to C phase 0 volts.

C phase to A phase 0 volts.

Two phases to neutral are still available to maintain a limited supply.

I disagree! You maybe trying to say that a blown primary fuse creates an open-delta condition, which it does not, but then the voltages you claim make no sense. With a blown primary fuse the magnetic flux in two of the three transformer windings (cores) is significantly reduced by approximately 50%, therefore you cannot have normal 220V on those two secondary phases.

[electau]

With a typical Delta-Wye residential transformer, the loss of a HV primary fuse will cause low voltage on two secondary phases.

With a delta HV and star LV when there is loss of one HV phase the voltage on the LV will be,

LV eg. A phase to neutral 220V

B phase to neutral 220V

C phase to neutral 155V. ie 220/1.414.

A phase to B phase 380V.

B phase to C phase 0 volts.

C phase to A phase 0 volts.

Two phases to neutral are still available to maintain a limited supply.

I disagree! You maybe trying to say that a blown primary fuse creates an open-delta condition, which it does not, but then the voltages you claim make no sense. With a blown primary fuse the magnetic flux in two of the three transformer windings (cores) is significantly reduced by approximately 50%, therefore you cannot have normal 220V on those two secondary phases.

You are quite correct, one forgot that on the delta side there was a V connection caused by the lost phase supply.

A to N 220. B to N 155 C to N 155.