3 Phase run on 2?

Can a 3 phase motor run on less?

I have a washing machine that uses 1 phase through a "phase converter" to run a 3 phase motor. It has mofets and a controller which I imagine is used to create the phases and I'm wondering if one of the fets is "bad"(or weak) that it could still somehow allow the motor to turn(Even if only very slow).

I'm asking this because I don't want to have to check all the fets(because they are hard to get to and require desoldering) but I know the motor "works" at least somewhat(but somewhere there is a problem. i.e., the motor does spin a little on one of the cycles but when it is suppose to rev up for the spin-cycle it doesn't and throws and error and the motor speed.

Reply to
Jon Slaughter
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Do you really think something is wrong with the motor or its controller? Does the wash cycle work ok? If so, it sounds to me like there is some kind of sensor that measures how fast the drum is spinning. It's probably not generating a pulse train and the computer is shutting it down since it can't tell how fast it's going. Find and clean the sensor, it's probably optical. Do you have a scope?

Reply to
Anthony Fremont

Yes and no...a 3 phase induction motor won't be self starting with one phase missing (it may rotate slowly). If you spin the shaft manually it will come up to speed.

Reply to

Three phase motors can run on two phases with a 1/3 reduction in power. However its not as simple as just leaving off one phase. The motor can be started using a capacitor start for the missing phase. The are some circuits online but I don't have time to search now.


Reply to
Tom Biasi

Potentially but I do not think there is any senser on the basket because in the tech docs it mentions nothing about that. It uses the tachometer on the motor to sense the speed and gives the error about it either being the tachometer, mcu or ccu.

Point is, that it's not even starting to spin up on the spin-cycle... nothing... not even 1/10 of an rpm.

Yet on the drain part it does spin up, at least for 1 second or so for maybe

30 rpms. I think this is always what it did though.

(look at my other post in s.e.d about it)

I'm pretty sure it's the mcu though because on the drain I get a about 100V across the different phases on the output of the mcu but on the spin-cycle I get absolutely nothing but some noise from the relays and such. (which might indicate something wrong wtih the filters or power supply?)

The point is that the mcu works some of the time but not in almost identical circumstance in other times. (the difference being current and time... yet it should at least start)

Reply to
Jon Slaughter

Have you measured the 3 voltages? A voltmeter can't show the phase relationships, but if the magnitudes are equal, the fault is probably in the washing machine.

Reply to
Stephen J. Rush

You most likely have shorted FETS on the output, we had a guy bring his drive board in from a washing machine that employed a driving system like you are detailing. It was starting up in a slow state or he had to move the drum a little to get it to start until it finally just started to blow fuses on the board.

You may also want to check the motor it self. He also had to replace a motor in his dryer unit which was of the same type and these units were matching washer and dryer.

I bet you have the same models.

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Reply to

The problem was a resistor that was blown(was hard to tell) it was the first resistor in the path of the tach to the uP which basically was part of a voltage divider into a programmable voltage reference

Tach | R1 |

+---- Vref | |R2 | Gnd

R1 was open so my guess is that it was always showing that the motor was turning as fast as possible(inverted output I think).

I replaced R1 with exactly(by stacking resistors) what it had (470Ohms) and it works 100% better but every once in a while it still gives the F06 error.

Hence I think it's basically a threshold circuit that does something(not sure because a pretty large transistor and several small ones are after the Vref) that might include giving the F06 error.

Hopefully by decreasing R1 I can increase the threshold so it doesn't "trip" as much... either that or make it worse.

Reply to
Jon Slaughter

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