I have a motor that is designed for non-US power. It expects 380 volts, three-phase (with 220 volts phase-to-neutral). Feed is 220 volts three-phase Delta. Power is 3 KVA. Can anyone recommend a source for a boost transformer?

See: http://www.federalpacific.com/literature/drytrans/FPTS-RTB-0701.pdf About a dozen pages in is a good reference for figuring size and connection of buck/boost transformers. Operating 50Hz motors on 60Hz power may not always work too well. In some cases, it may be easier to change the motor.

haitijim,

You might not be able to use a simple Voltage Boosting Autotransformer setup for this situation, since the available Voltage is 220 VAC, and your Motor needs 380 VAC.

The only "Booster" setup would require a Secondary Voltage of at least 160 VAC.

In this situation, you may need to just settle for a normal Isolated Transformer (Primary and Secondary not connected as an Autotransformer), and adjust output via "% Voltage Taps".

Please reply if you would like additional information, or more web sites for Transformer Manufacturers.

Scott35 S.E.T.

Can the motor be reconfigured for delta operation (220V phase-to-phase)? It's possible on some European motors.

Great suggestion, C-H!!!
If the windings can be connected as a Delta (currently Wye), this should drop the required input voltage from 380 VAC to 220 VAC (219.3995...VAC to be exact).

If the Motor doesn't mind an increased input voltage of between 4% (230 VAC) and 8% (240 VAC), then no boost transformer would be needed!

Another thought:
Does this Motor have Split Windings? (AKA Dual Voltage Motor).
Find this either on the nameplate, or by verifying if there are 9 Motor lead terminations.
Typical 3Ø Squirrel Cage Induction Motors for 60Hz US stuff would be connected as follows (for a Wye connection of stator coils, each split coil in series - or setup for Higher rated voltage):

T-1 to "1",
T-2 to "2",
T-3 to "3",
"4" to "7",
"5" to "8",
"6" to "9"

Scott35

I used to work at an Amusement park and our German rides had motors of that configuration.

When I started they were running at 208 volts but they were dogs trying to accelerate the rides so we used buck boosts to get the voltage to 230 and all was good.

[This message has been edited by iwire (edited 03-15-2003).]

Thanks to all who have responded. My motor is made in The Netherlands and has this on nameplate:
Mfg. = Overveld
Type 4PT090L
Volts: 220/380
1.5 KW
1410 RPM
6.9/4 amps
0.77 PF
IP = 54

My power source measures 220 volts phase-to-phase and 127 volts phase-to-neutral.

The motor has 6 leads. Label says it can be connected Delta or Wye. I thought this means:
-If connected as Delta, 380 volts phase-to-phase should be used as power source.
-If connected as Wye, 220 volts Phase-to-neutral should be used as the power source.

Since 380 volts/sqrt(3) = 220 volts, could I use three single-phase, 1:1 transformers with each primary connected from phase-to-phase of my source and the secondaries connected as 220 volts Wye. If I understand the nameplate voltage rating correctly, this should work. I realize there is an issue with motor speed, but that is not critical in the application.

I would appreciate any enlightenment. Haitijim

Haitijim- Try this connection, Delta, L1-U1 & W2, L2-V1 & U2, L3- W1 & V2. This should work at 220 / 3 phase . Are your leads make like this?

haitijim,


Cool! You do not need any Transformers (unless your AC system is a 4 wire Wye system and the Motor needs exact voltage).

Connect the Motor leads for the lower rated Voltage (220 VAC), and drive the Motor directly from your 3Ø System.

Must be a 50 Hz 4 pole Motor, judging from the 1410 RPMs! On 60Hz, this Motor will run at 1725 RPMs @ Full Load output.

Like that Power Factor of 77%!

The FLA figure of 6.9 Amps is what the Motor would draw at 220 VAC-50Hz, when 1.5 KW is drawn from the supply (and the output HP = 2 HP).


No problem! The grounded Neutral Conductor is not used here - only the 3 Ungrounded Conductors (ØA, ØB and ØC).

Before I go any farther, are you reading 220 VAC on a DVM? Are you sure this system is 220 VAC and is 3Ø?
If so, you would find the following readings between Line and Ground (or Neutral):

ØA to Ground / Neutral: 120 VAC (+/- 5%),
ØB to Ground / Neutral: 208 VAC (+/- 5%),
ØC to Ground / Neutral: 120 VAC (+/- 5%),


If all three are 120 VAC to ground, you have a 4 wire Wye - with 208 VAC across the Ungrounded Conductors (ØA-ØB=208 VAC, ØB-ØC=208 VAC, ØA-ØC=208 VAC). In this case, you may want to boost the voltage up another 12 VAC, via an Open Delta booster configuration of two 250 VA Transformers.

If you only have 1Ø 3W service, you are out of luck!

Scott35

Scott, the 127/220V wye is the old European system which still is in use in some parts of the world. (Mainly Brazil) Your suggested readings would apply to a 240V center tapped delta system.

Thanks again for all your comments and information. I think I'm beginning to understand. My earlier post that said:

"The motor has 6 leads. Label says it can be connected Delta or Wye. I thought this meant:
-If connected as Delta, 380 volts phase-to-phase should be used as power source.
-If connected as Wye, 220 volts Phase-to-neutral should be used as the power source."

Bbecause of my misconceptions, I now think the above statement was incorrect. What I now think 380/220 means is:

-if you have a 380 volt three-phase Delta feed, you connected the motor leads for a WYE.
-If you have a 220 volt three-phase delta feed, you connect the motor as a delta.

In both cases, the actual voltage that appears across one of the windings is 220 volts. If this is not correct, please tell me.

The next part of my problem is determining exactly what feed I have. The panel box has three hot leads and a neutral. Using a DVM (true RMS), I read these actual voltages:

ØA to ØB: 223 VAC
ØB to ØC: 220 VAC
ØA to ØB: 219 VAC
ØA to Neutral: 129 VAC
ØB to Neutral: 130 VAC
ØC to Neutral: 124 VAC

I cannot be sure it is true three-phase because I did not measure phase angle. My best guess is this is nominally 220 volts phase-to-phase which should give 127 volts from each phase-to-neutral if the supply is a true Wye (neutral not from a tapped Delta). Due to various other load imbalances connected to the system, I am not getting exactly 127 volts

The final problem is what to do about 50/60 Hz. Assuming the speed increase I get by operating a 50 Hz motor on 60 Hz is not a problem for the application, do I need to increase voltage to the motor by (60-50)/50 = 20% to compensate? 220 VAC * 20% = 44 volts. 220 + 44 = 264 VAC?

Obviously I'm new to three-phase motors, so all suggestions/comments are welcome. HaitiJim

Yes!


Where are you? Haiti? It would be an unusual system in the US, but not outside it. (That's why they design the motors for it. )


If you need the full torque. If the motor is oversize for the application, it might not be necessary. If you increase the voltage you will get more power, which means more heat dissapated in the motor. This doesn't have to be a problem as the fan inside the motor will also rotate 20% faster, improving the cooling.

{Edited after rereading Jim's post to remove irrelevant info}

[This message has been edited by C-H (edited 03-16-2003).]

Thanks for everybody's help. I do volunteer work in Haiti, but live in the US. This project is part of an effort to eradicate a disease called elephantiasis caused by a mosquito borne parasite, filariasis. (http://www.nd.edu/~ndmag/sm2001/Haiti.html}Table salt is treated with both iodine and a chemical called diethyle carbamazine and distributed to affected areas. The machine for treating the salt uses two motors to run converyer belts and a motor driving a chemical sprayer pump. The voltage from the powerline is not well regulated so unless we can regulate input voltage to the machine, it will be difficult to get consistant dosage. With everybody's help, I think we have determined that if I wire the motors in Delta configuration, I can use the existing 220 volt, 60 Hz, three-phase. I may try the suggestion to boost the 220 volts to compensate for the 50 to 60 HZ frequency change. Does anybody have recommendations for how to stabilize voltage? I am considering a Lenco three-phase ferro-resonant transformer; 220 volts, three phase in to 220 volts, (or 220 x 1.2 = 264 volts), three phase out. HaitiJim

The speed of the motors will be determined by the frequency and load rather than the voltage. Luckily, the frequency is usually rather stable, but in a poor country like Haiti I would expect it to vary up to +/-5%, maybe more.

An unstable voltage indicates some additional problems: The motor is only designed to handle a certain undervoltage (10% or similar). Even if you boost the voltage 20% to accomodate the higher frequency, the motor could still be damaged if the supply voltage falls. The impedance of the distribution network is often high in poor countries, meaning that a large load (like the motors) will cause the voltage to drop considerably below what you measured.

To make matters worse, if the phase-to-phase voltages aren't within 2% of each other the motor will run hotter than normal.

All of these potential problems can be addressed with transformers, variable frequency drives and other tricks. But before you run out and buy these things: Check how much they cost. There might be a simpler solution: Putting in one size larger motors. A 4 KVA motor is not very expensive.

The cheapest solution is to see if the load on the conveyer belts can be reduced and run the existing motors off the existing 220V.