noise related problems in motor switching

[vu2gmc2000]

I have a processor controlling a contactor for switching on a 3 phase motor. Whenever I switch on or off the contact(mostly when switching off) the processor hangs. Sometimes the processor is working but the LCD display blanks out. How do I protect from this. What snubbers should I put on the motor contactor or coils ?

 

[jpsganesh]

put decoupling capacitor near to controller at all power pins.
make a proper controller reset pin circuit.
avoid placing controller near HV line and EMI/EMC generating items.

 

[vu2gmc2000]

Ganesh,
All these precautions have been taken. The controller is housed in a metal cabinet which is earthed. power supplies for the controller and the Ios/Drives etc are mutually isolated. This is purely a switching noise problem and I need to find out a suitable snubber circuitry with proper values. Maybe the solution will vary case by case depending on the motor specifications.

 

[jpsganesh]

s. u can try by changing snubber ckt values.

put decoupling capacitor near to controller at all power pins.
make a proper controller reset pin circuit.

did u take care of these points?

 

[vu2gmc2000]

yes, the system is otherwise protected with TVS diodes on all IO lines, ferrite beads and PI filters on io lines, common mode pwer line filter etc. It is only the contactor switching the motor which is causing this problem. I'm experimenting with snubber ckt values. Will let you know the results when I have them.

 

[jpsganesh]

ok. let u know if I got any other solution for this and let me search in google too.