Overload protection on a DC motor

[controlled]

I have a small paper winder that is driven my a WER DC drive feeding a 250 Vdc motor. This is a fairly old machine that is not certified (CSA, UL, MET).

It is a law in Ontario that every piece of equipment be certified before it is put in service.

I had a field inspector look the machine over, and he stated it needs a contactor and overload installed between the drive and the motor. I am fine with the 2 pole contactor, but I'm not sure about the overload. Should it monitor both the armature positive lead and negative, or just the positive.

Any suggestions would be appreciated.

 

[Clay B.]

Generally one is enough. I prefer 2 myself due to the posibility of one side grounding out prior to the brushes.

Or if your motor has feild windings and is not a permant magnet style I would definatly use 2.