Running 120V Motor with 240V?

use a stepdown transformer

If you're using power electronics, then by the time it gets to the motor it's 120V, and the onus is on the electronics to make it fly and not fry.

How big is it? Split phase? Offshore-made autotransformers are reasonably priced up to 500W or more (>1/2 HP), but they're heavy. Best regards, Spehro Pefhany

Check the manufacturer's specs. Some motors have provisions for connection as either 120V or 240V. Sometimes you will see a wiring diagram on the inside of the motor junction box cover plate. You might get lucky! Jon

Thanks for the suggestions.

I'd rather not use a step-down transformer if I could avoid it (They're a little big, and I'm not sure I have the room).

It's a PSC motor.

Thanks

It does not support rewiring as 240.

Do I have any options other than a transformer?

Thanks

It does not support rewiring as 240.

Do I have any options other than a transformer?

Thanks

You might get away with a series capacitor, but guard against LC series resonance at or near the supply frequency.

Chris

"Mio" wrote in message news: snipped-for-privacy@e53g2000hsa.googlegroups.com... On May 14, 12:05 pm, jd snipped-for-privacy@yahoo.com wrote:

It does not support rewiring as 240.

Do I have any options other than a transformer?

Thanks

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If you want to be creative, you could make a PWM motor controller, but instead of rectifying the mains voltage and recreating a sine wave, you can drive the bridge with the sine wave input and use diodes to steer the voltage appropriately. Then you can use a simple 50% PWM to get 120 VAC from 240 VAC.

I did something like this with LTspice. The ASCII file shows generic switches that need to be replaced with a bidirectional switches, which could be two MOSFETs or IGBTs in series. The same effect can be done in a bridge circuit. If the load is inductive, as a motor, it is necessary to provide a conduction path during the OFF times, and the snubber reduces inductive voltage spikes during transition. The RC network across the load shows the average waveform that effectively would be seen by the motor.

Paul

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Version 4 SHEET 1 880 680 WIRE 64 -32 -320 -32 WIRE 16 0 -256 0 WIRE 64 0 64 -32 WIRE -16 48 -48 48 WIRE 0 48 -16 48 WIRE 224 48 80 48 WIRE 304 48 224 48 WIRE 400 48 304 48 WIRE 448 48 400 48 WIRE 560 48 528 48 WIRE 592 48 560 48 WIRE 96 96 -176 96 WIRE 400 96 400 48 WIRE 464 96 400 96 WIRE 224 112 224 48 WIRE 400 112 400 96 WIRE 464 112 464 96 WIRE 176 128 -128 128 WIRE 592 128 592 48 WIRE -256 160 -256 0 WIRE -176 160 -176 96 WIRE -48 160 -48 48 WIRE 48 160 -48 160 WIRE 304 160 304 112 WIRE -48 176 -48 160 WIRE 48 176 48 160 WIRE 96 176 96 96 WIRE 176 176 96 176 WIRE 400 208 400 192 WIRE 464 208 464 192 WIRE 464 208 400 208 WIRE -320 272 -320 -32 WIRE -256 272 -256 240 WIRE -256 272 -320 272 WIRE -176 272 -176 240 WIRE -128 272 -128 128 WIRE -128 272 -176 272 WIRE -48 272 -48 256 WIRE 48 272 48 240 WIRE 48 272 -48 272 WIRE 224 272 224 192 WIRE 224 272 48 272 WIRE 304 272 304 240 WIRE 304 272 224 272 WIRE 400 272 400 208 WIRE 400 272 304 272 WIRE 592 272 592 192 WIRE 592 272 400 272 WIRE -256 304 -256 272 WIRE -128 304 -128 272 WIRE -48 304 -48 272 FLAG -48 304 0 FLAG -16 48 Vin FLAG -256 304 0 FLAG -128 304 0 FLAG 560 48 Vout SYMBOL res 288 144 R0 SYMATTR InstName R1 SYMATTR Value 20 SYMBOL cap 288 48 R0 SYMATTR InstName C1 SYMATTR Value 0.47µ SYMBOL voltage -48 160 R0 WINDOW 3 23 136 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 16 99 Left 0 WINDOW 0 30 28 Left 0 SYMATTR Value SINE(0 360 60 0 0 0 150) SYMATTR SpiceLine Rser=1 SYMATTR InstName V1 SYMBOL sw 96 48 R90 WINDOW 3 -36 -113 VRight 0 WINDOW 0 24 92 VRight 0 SYMATTR Value MySwitch SYMATTR InstName S1 SYMBOL voltage -256 144 R0 WINDOW 3 -91 241 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 0 9 7 Left 0 SYMATTR Value PULSE(0 10 50u .1u .1u 49.8u 100u 3000) SYMATTR InstName V2 SYMBOL sw 224 96 R0 WINDOW 3 -12 117 Right 0 WINDOW 0 24 92 VRight 0 SYMATTR Value MySwitch SYMATTR InstName S2 SYMBOL voltage -176 144 R0 WINDOW 3 -171 205 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 0 7 7 Left 0 SYMATTR Value PULSE(0 10 0 .1u .1u 49.8u 100u 3000) SYMATTR InstName V3 SYMBOL res 384 96 R0 SYMATTR InstName R2 SYMATTR Value 100 SYMBOL res 544 32 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL cap 576 128 R0 SYMATTR InstName C2 SYMATTR Value 100n SYMBOL ind 448 96 R0 SYMATTR InstName L1 SYMATTR Value 100m SYMATTR SpiceLine Rser=10 SYMBOL cap 32 176 R0 SYMATTR InstName C3 SYMATTR Value 10µ TEXT -88 496 Left 0 !.tran 100m startup TEXT -416 464 Left 0 !.model MySwitch SW(Ron=.1 Roff=100Meg Vt=2 Vh=-.5 Lser=10n Vser=0)

A simple phase control that employs a triac will work just fine.

Not safe.