I want to drive a 3 phase hoist motor. it work very simple, just rotate left ,stop than rigt (depend on the order there are 3 push button ; left,right and stop).
It seems work very good when i simulate it without the motor (just drive the relay).
but the problem arises when I put the hoist motor.
first I push the button 'left', the motor rotate to the left (that's a good start)
then I push the button 'stop', the motor stop, suddenly it rotate again (randomly, may be to the right, may be left)
I repeat this (rotate left then stop) for about 20 times, the errors occured 16 times !!!
I check the program... that's nothing wrong (i hope)


I courious about the electromagnetic wave that produced by the hoist motor,
is that true???
can somebody tell me why this is happen?
how to solve it??

thanks,

Ridwan Efendi