Dear Suhas,

I understand what you want. But be forewarned on a few issues :

1. You can use either a step down transformer or a direct voltage divider network across mains + bridge rectifier + minor smoothing and compare the levels with LM339 or similar and switch off motor when voltage is outside the correct "window".

2. Dont forget a time delay to initiate the cut out action. Otherwise you know the consequences. So far so easy...

3. Now comes the real issue - having cut out, how do you cut in again? Here also a time delay will be required, say 5 or 10 secs - but still you can end up with frequent start / stops if the voltage swings very badly.

So the best is to have Manual cut in when the system has cut out. OK this may not be feasible / desirable in some cases.And the discussion continues....

Raghu