motor rotation verification

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ALC#1

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austin, tx.
Is ther any other foolproof way of verifying correct motor rotation on a three phase motor other than "bumping" it? If motor was preciously connected to another source a phase rotation meter can be used on the previous source and the source that the motor is to be connected to for verification. Is there any other method that anyone is aware of?
 

kingpb

Senior Member
Location
SE USA as far as you can go
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Engineer, Registered
Is ther any other foolproof way of verifying correct motor rotation on a three phase motor other than "bumping" it? If motor was preciously connected to another source a phase rotation meter can be used on the previous source and the source that the motor is to be connected to for verification. Is there any other method that anyone is aware of?

If the load would not be damaged by running the motor in reverse then you can bump it. But there are loads that could be damaged by reverse operation, and then using a phase rotation meter is the only way. Not only should you check the motor, you should also check the source. There are standard methods and procedures for performing both these checks.
 

Strife

Senior Member
If the winding of the motor is done correctly, the phase rotation meter will still be accurate.
Other than that, I don't see any other way than bumping (if the winding is ACB all the tools in the world won't detect that until you turn it on)

Is ther any other foolproof way of verifying correct motor rotation on a three phase motor other than "bumping" it? If motor was preciously connected to another source a phase rotation meter can be used on the previous source and the source that the motor is to be connected to for verification. Is there any other method that anyone is aware of?
 
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texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Used to do some vertical turbine pump work, mostly in 100-200 Hp range. They typically have a ratchet mechanism so they don't back spin when they shut off which meant "bumping" isn't an option unless you temporarily remove the ratchet, especially with across the line starting. Years ago when we discovered motor rotation meters that was a big help, but I always removed the ratchet assembly and bumped it once just to verify.
 

masterinbama

Senior Member
If the winding of the motor is done correctly, the phase rotation meter will still be accurate.
Other than that, I don't see any other way than bumping (if the winding is ACB all the tools in the world won't detect that until you turn it on)

It doesn't matter how the motors wound. The meter in my link connects to the motor leads, you turn the shaft in the desired direction and it indicates the sequence.
 

masterinbama

Senior Member
Used to do some vertical turbine pump work, mostly in 100-200 Hp range. They typically have a ratchet mechanism so they don't back spin when they shut off which meant "bumping" isn't an option unless you temporarily remove the ratchet, especially with across the line starting. Years ago when we discovered motor rotation meters that was a big help, but I always removed the ratchet assembly and bumped it once just to verify.

If you're going to remove the ratchet mechanism don't forget to uncouple the impeller shaft also.

Otherwise on some vertical turbine pumps you run the risk of the impeller unscrewing itself and blowing out the bottom of the pump foot.
 

brian john

Senior Member
Location
Leesburg, VA
Is ther any other foolproof way of verifying correct motor rotation on a three phase motor other than "bumping" it? If motor was preciously connected to another source a phase rotation meter can be used on the previous source and the source that the motor is to be connected to for verification. Is there any other method that anyone is aware of?

Check your IM's
 
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