motor stuck on

[caribsub]

I control a 36 V, 36 amps DC motor through a relay rated 80amps 36 volts, to close the relay it is a secondary circuit that i switch on 12v , works fine but motor keep running when i cut the 12 V on the relay.Do i have to put a capacitor somewhere to absorb energy on the the secondary circuit
Herve

 

[UKpete]

caribsub- How long does the motor keep running, and are you saying that the relay fails to open?

 

[honjohnest]

Have the wiper on the relay go to the motor use the normally closed contact for the following: When the motor switches off, you may need to throw away the built up EMF energy through a power resistor or sometimes even a short circuit to stop the motor. I might suggest that you put three 12vdc bulbs in series across the motor and see how long they stay on after power is turned off. Home Depot has these bulbs which use standard lamp type sockets.

If you have a heavy mass rotating when power is removed you will need to put a heavy load (low resistance) across the motor to slow it down.

Good luck! John D.

 

[buzzp]

I would verify the contacts are not welded shut on the relay first. Then you should put a load on it as previously suggested.

 

[gmdh]

the relay fails to open, but is not welded shut, i have to actually open the circuit through the power switch which opens the relay and stops the motor.
I beleive it is EMF built up as suggested, i will try resistor, i thought diodes or capacitors. I need it to stop instantly.
Herve

 

[1x1x1x]

How long is your 12 V control wire? If the main contacts of the relay is not welded it is possible the the relay winding may stay energize by the 12 volt control wire capacitancealso make sure the yor 12 volt relay coil is energized by dry contact.

 

[jbartos]

Suggestion: Motors that are designed for instant stoppings, beside an electromagnetic brake application, may need to be rated for the plugging duty. Namely, the plugging can stop motor instantly and ultimately, it will reverse its direction of rotation. This can be prevented various ways, e.g. mechanically or by the duration of the plugging mode.