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Motor Rotation Causes Due to One Phase Lose?

06/20/2011 10:59 AM

Hi, can anyone answer me what is the problem of this?

We have driving device, which is using by 3 phase, single cage type, induction motor controlling by forward reversed stator ( 2 contactor ) and protected by torque switch and limit switch.

My problem is like this, when motor can ran close, about to reach close limit (before cut off, both torque and limit switch not activated yet), the motor ran in reverse direction even when close contactor still being energized. Suspect higher current draw when reaching close limit caused this symptom. This fault can always be simulated whenever we get the motor to run in close direction. We cannibalized another contactor from spare and installed. Tested ok.

So i would like to understand what is that problem cause by that contactor only energized and motor is reversed without changing another contactor.

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#1

Re: Motor Rotation Causes Due to One Phase Lose?

06/21/2011 12:37 AM

Three phase motors need all three phases to run reliably. If one phase is lost, it normally will not start, but if it is already running when one phase is lost, then it may continue running under light load. Occasionally an excessive reverse torque will actually make the motor run in reverse. Again, if the load is light, it may continue running in reverse.

"...controlling by forward reversed stator ( 2 contactor ) and protected by torque switch and limit switch." This is not clear English. Does this mean there are 2 3-pole contactors, where the term 'contactor' indicates a heavy-duty relay? That would be standard for reversing a 3 pole motor. Or does it mean the switching device reverses 2 contacts. This kind of reversing switch should only be changed when there is no power to the motor, and the motor is fully stopped.

Finally, due to the limited English, I'm not entirely sure that this is a true three-phase motor. If not, there are lots of other possibilities...

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#2

Re: Motor Rotation Causes Due to One Phase Lose?

06/21/2011 1:30 AM

when you say "close" are you referring to a limit switch on a door or something like that and its the direction that the motor is moving "a door" up.... to open, or down... to close?

I too think you do not have a 3 phase motor. A 3 phase motor that has a forward-reverse contactors for clockwise/anti-clockwise rotation has only two contactors, electrically and mechanically interlocked, with TWO start buttons (Forward & Reverse, or Open & Close, or Up & Down) plus a Stop button. Then into that simple control circuit, limits are introduced.

So there is no way your motor would/should run in the opposite direction if opposing contactor is energised.

It sounds like you have made this yourself, I suggest you scrap it and buy "off the shelf" a "fit for purpose" DOL starter with reverse contactor and use a real 3 phase motor.

To answer you question..what is that problem cause by that contactor only energized and motor is reversed without changing another contactor.

I think your contactors are single phasing.. that is NOT all three phases if you do have 3 phase are closing and if the motor has only two phases it will run in any direction its decided to, and that can be influenced by the load on the shaft/gearbox, hence it going the opposite way you want it to.

So we are back to my earlier statement, buy a "fit for purpose" unit!

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#4
In reply to #2

Re: Motor Rotation Causes Due to One Phase Lose?

06/21/2011 11:49 AM

thanks for replying to me.

actually that is motor operated Valve.( Actuator)

that contain in 3 phase ,single cage type motor, PCB electronic circuit, 110V contactor. ( not relay)

electronic PCB circuit, that will be produce 110V output for contactor coil to energize and de energize.(2 contactor for Close and Open) when command is given . Once command is given,(either open or close) electronic circuit is take action and give output of 110V for energize that contactor coil. contactor coil is energize, aux contact will be taking for 3 phase supply (U V W ) to motor terminal . U V W.

Scenario:

i found out , when give close command , 110V is coming from PCB and close contactor is energizing, Aux contact that from these contactor will be take 3 phase supply (U V W) to motor terminal and motor was run for close action to that valve. after that nearly to reached valve is shut,( at the time, torque will be rising up for fully shut to that valve). motor rotation was changed and this contactor was continuous energized and valve will be open back.

so i was issued for that contactor to replacing another one. ( same model contactor)

after that OK.

so i want to kn0w, that contactor is energizing why motor was reversing didn't change yet another phase shift . (i suspect for that contactor, so i changed.). So if one phase lose, that 3 phase motor will be change another direction ? during increasing load.

thaks,

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#3

Re: Motor Rotation Causes Due to One Phase Lose?

06/21/2011 1:32 AM

Your heading...."Motor Rotation Causes Due to One Phase Lose?"

Just noticed it.. so you know you are loosing one phase.. you have answered your own question!!

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