Damaged 480V 3-Phase motor reconnected for 240V?

[Tip DS]

Scenario: 240/480V 3-Phase Y-wound electric motor has a damaged 3-6 coil. Can the motor be re-connected from its 480V configuration to the 240V configuration (bypassing the 3-6 winding [and the 1-4 & 2-5 windings]) and be salvaged for temporary use at 240V?

I realize the motor will have to run a higher current at the lower voltage. Assuming the voltage and current can be supplied, is this a workable solution to keep the motor on-line while a replacement is obtained?

 

[kwired]

If driven load is somewhat minimal for the rating of the motor you can get by. The more loaded the less run time you will have to get a replacement. You possibly can have a hard time starting if your load requires high starting torque. Variable torque loads like centrifugal fans and pumps is where it is likely to last the longest.

 

[Tip DS]

If driven load is somewhat minimal for the rating of the motor you can get by. The more loaded the less run time you will have to get a replacement. You possibly can have a hard time starting if your load requires high starting torque. Variable torque loads like centrifugal fans and pumps is where it is likely to last the longest.

Yes, I probably should have stated that; it is for a centrifugal pump. Thank you for your input.

 

[kwired]

I'm not certain if or how much counter forces this open phase on half the motor will put on the motor but is possible to leave 1-4 and 2-6 disconnected as well then you essentially have a motor with half the nameplate output rating. Might need to partially close a valve or something to keep the load low enough to not overload what you have left of a motor.

 

[winnie]

It might be possible to cut a completely open section of the winding out of the motor. It is not clear if you should cut the corresponding part of other phases out or not; because it isn't necessarily specified which part of the stator is energized by which winding terminals.

But IMHO the big question is if you really have a completely _open_ coil. If you've had a winding failure, you very likely have damage to the insulation of multiple turns of wire, and very likely have shorted turns of wire in the motor. Energize other coils and you will quickly see more failures.

If it is absolutely essential to get this motor working on a temporary basis while getting a replacement, then I'd suggest getting a rewind shop to look at the damage.

-Jon

 

[kwired]

It might be possible to cut a completely open section of the winding out of the motor. It is not clear if you should cut the corresponding part of other phases out or not; because it isn't necessarily specified which part of the stator is energized by which winding terminals.

But IMHO the big question is if you really have a completely _open_ coil. If you've had a winding failure, you very likely have damage to the insulation of multiple turns of wire, and very likely have shorted turns of wire in the motor. Energize other coils and you will quickly see more failures.

If it is absolutely essential to get this motor working on a temporary basis while getting a replacement, then I'd suggest getting a rewind shop to look at the damage.

-Jon

Rare but I have had just one winding with open circuit before like OP describes. One I can specifically recall was a grain auger motor (dual voltage) operating at 240 volt three phase. Since windings are in parallel on low volts on dual volt motors, this one kept running but what prompted them to have me look at it was frequent overload tripping. When investigating I discovered one coil of the six coils was open. This allowed the motor to still run since the other winding that is parallel to the effected winding still worked. Been a long time ago so I don't recall many other details but I do know it still worked, and maybe even worked for significant amount of time if not mechanically loaded too much before motor overload would trip.

Pretty sure we replaced that motor general rule is 10 HP and below are not worth rewinding unless they are something other than a general purpose two, four or maybe even six pole design. Special frame or shaft - rewinding becomes more of an option even on smaller motors sometimes.