testing motor direction

[Brant]

I have been asked a question on motor rotation dose anyone know of a test the can tell the direction a motor will rotate when it is conected to a 3 phase supply with a known phase rotation (motor leads not marked)the question was asked to aviod starting large drive the wrong direction when connected to gear boxes with roll back protection

 

[jbartos]

This appears to be a difficult case since there is no way you can determine the motor rotation direction without testing it; whatever it may require to implement it. Suggestion: The disangagemet of gear from the motor gearbox is a good idea. Another way would be to gradually apply increasing voltage while monitoring current in the motor leads. If the current increases more in one phase sequence connection than in the other, then the direction of rotation is incorrect. However, this could potentially damage your gear. It would have to be analyzed first whether or not it is safe to the gear.

 

[peterb]

There are commercially available testers for this purpose. Check the AVO International website:

http://www.avointl.com/products/rotating/rotate.html

 

[jbartos]

The tester appears to be good up to 600V. The original post does not indicate the motor terminal voltage.

 

[peterb]

The tester will not be connected to the energized motor, so the voltage is irrelevant. Test is done with the motor stationary - two tests at two different rotor angles, with the rotor shifted in the direction of correct rotation. This particular tester is also used to determine system phase rotation and will have a limit of 600 V for this application. I believe that this type of device will do the job for you, Brant.

Quoting from the website data :
"....Phase Rotation Tester permits the electrical contractor or industrial maintenance electrician to permanently connect and tape the terminals of the motor being installed, without having to first energize the motor by a temporary hookup from a power source, if available, to determine motor rotation. Therefore, the test set eliminates the need for temporary connections that can be time consuming, costly and quite hazardous, particularly where many large, high-voltage motors are involved.

"Also, certain types of drives should never be rotated in the wrong direction. In such cases, the temporary hookup or trial method, having a fifty-fifty chance of being wrong, can do serious harm."

 

[jbartos]

It appears that the input supply phase sequence at the motor terminals is needed to determine the motor rotation with respect to the motor supply phase sequence. What if is the supply phase sequence changed? Then motor will turn in the other direction. This would imply that the input supply phase sequence correlation the the motor direction of rotation is needed. This is why there is a concern regarding the complete determination of the motor run in the specified direction and associated motor rated/terminal voltage with respect to the mentioned meter 600V rating. There is to be noticed that the motor leads are not marked.

 

[peterb]

Original post states that the 3 phase supply rotation is known. The test set identifies the correct motor lead connections to be matched to the known supply phase sequence to obtain the desired physical rotation.
If the supply phase sequence is required, it is determined by using the meter up to 600V. If the circuit voltage exceeds this value, then voltage transformers are needed to utilise the meter - note that this is a standard practical test used for determining phase sequence at any voltage. If the circuit does not include VTs, then a temporary installation is needed.

 

who makes these testers and at what price are they ?
And are they available for d.c motors.

 

[jbartos]

Suggestion: Visit

http://www.avointl.com/products/rotating/rotate.html

for AVO International product by clicking on Motor and Phase Rotation Tester and accessing *.pdf file containing Specs