dc voltage supply for small dc shunt motor

Thread Starter


Joined Mar 24, 2006
Trying to build field voltage source for 115 volt dc. Motor is only 1/50 hp shunt.
Armature current is .33A. Don't know what field current is.
From 120v ac source, connecting a bridge rectifier and smoothing capacitor of 1000uf. I think dc voltage would be 1.414 X AC source voltage? If so, I would need to decrease the voltage in this circuit to the field by about 52 volts.
I don't know what the resistance of the field winding is and need to determine that.
I was then going to pick a resistor or rheostat and put it in series with the field . . . picking the resistor for a 50 v drop. If I used a rheostat, I could adjust the voltage to the field.
I don't need any motor field protection.
I have not done anything like this before and am wondering if I'm on the right track. Any advice would be very welcomed.