Closing Coil Failure in Vacuum Contactor 1

[charz]

The closing coils in a vacuum contactor are getting failed repeatedly. Latched type vacuum contactor, so there is continuous power supply to the closing coil.
Coil Voltage:110 V DC
The 110V DC is rectified DC from 110V AC. The Input to the rectifier is from a control transformer. The rectified DC has a smoothing capacitor. The capacitor has a rating of 150V, 220uF.

Does the filter can cause over voltage to the closing coil? or could the switching surges can cause the coil failure?

Any comments/experience.

 

[ppedUK]

A closing coil for a latched contactor is short time rated and not intended to be energised all the time that the contactor is closed. On the other hand, a DC coil for an electrically held contactor is continuously rated, but often also has an "economy" circuit which reduces the coil current once the contactor has "sealed in". If the economy circuit isn't working when the contactor is closed, the coil will eventually burn out.

 

[Zogzog]

Check the magnets for proper alignment/adjustments per the IB and make sure the surfaces are clean

 

[charz]

Latched type contactor, so there is NO continuous supply to the contactor - a correction to my original post. If there is voltage spike during switch off, Is it possible that coil gets burnt, usually the contacts above the coils gets welded etc.

 

[ScottyUK]

110V AC through a full-wave rectifier and smoothing cap will produce about 155V DC or so. Your cap is in trouble, and I can hazard a guess why the coils might not be too happy.

Your transformer secondary voltage should be around the 80V AC mark to produce 110V DC. With that said, 220uF is a fairly small capacitor - how much current do the trip and close coils draw?

 

[krisys]

I remember the vendors normally provide a free wheeling diode or a spike absorber kind of thing across the coil. Consult the vendor.