How Do You Isolate Supply of a Motor?

[jonnyc55]

I got some homework for electronic engineering. I have to provide steps on how to work on a motor. One of the steps is isolating the supply the next one is isolation lock, there is also a step on testing isolation of motor, what could i write for this aswell .

Am not sure on what to write for them :S. Any advice will be brill.

Thanks.

 

[telectrix]

generally, a motor will have a local isolator. these generally have the facility to be locked off with a padlock. to test for isolation, open terminal cover and test each phase to neutral ( if you have one) and to earth with an approved tester.

 

[jonnyc55]

Thanks for the reply. However i stuck on what you said for testing for isolation. I dont know what you mean by test each phase to neutral.

 

[Sintra]

Remember to prove the voltage tester both before and after testing at the motor.

 

[telectrix]

some motors have a neutral, some don't. i always test anything phase/earth as if you have a missing neutral, you may wrongly think the circuit is isolated when it aint. and don't forget the good old votstick as a first indication, but don't rely on it. and as sintra says, always test your tester on a known live supply first. it,s got a battery in it which could be flat or duff. as always, better to take an extra few minutes making sure than letting them quacks at the locaL butchery mess about with you.

 

[jonnyc55]

Ok thanks alot! for the reply, would you know anything on the above question for a pole transformer?

 

[telectrix]

pole dancers yes, transformers not a lot

 

[jonnyc55]

Haha well.. wish my homework was on pole dancers.

 

[alkajones]

I hope this will help.

Check it is safe to isolate motor.
Determine isolating point for motor.
If you’re working on a large machine ensure your isolating correct panel. (Check labelling of motor/cable if any against drawings, etc).
Isolate.
Lock off.
Place Key in pocket.
Place warning signs.
Ensure safe access to motor.
Make sure motor is not to hot to work on.
Note motor name plate for motor type.
Remove motor terminal cover carefully
If motor has burnt out avoid inhaling dangerous fumes.
If no name plate or drawings do visual on motor terminations to determine motor type.
Use suitable voltage instrument.
Check instrument is working correctly against known voltage supply.
Test between all line, neutral and earth points.
Prove test instrument once more.
Do visual on terminations, cable entry points and mechanical soundness of glands for good earth continuity, etc.

[FONT=&quot]I’m no expert and probably left a few things out[/FONT]

 

[ian.settle1]

One thing which has not been mentioned is that whilst you may have isolated the connection for the motor be aware that some motors may also have connections for a heater which will become live when the motor is not running.