Start Capacitor sizing
Start Capacitor sizing
(OP)
I have an electric motor for a heavy duty drill press that is missing the Start Capacitor. The motor runs good and is in good shape, how do you determine the right start capacitor for this motor.
The specs for the motor is:
1 h.p.
60 hz
110/220 volts
16/8 amps
Single Phase
4 pole
Heat 60 deg C
Class A
1720 rpm
Any help would be appreciated!! Thanks
The specs for the motor is:
1 h.p.
60 hz
110/220 volts
16/8 amps
Single Phase
4 pole
Heat 60 deg C
Class A
1720 rpm
Any help would be appreciated!! Thanks





RE: Start Capacitor sizing
I can't tell you how to determine the correct value, but a book I have suggests 50uF/HP at 220V, four times this at 110Volts. It's an English book so probably 50Hz.
In my limited (non-professional)experiance of small motors it's not critical.
Peter B
uk
RE: Start Capacitor sizing
Inrush kVA * sin( cos^-1(pf)) = kVAR Cap. required.
Mike
I get 5.5kVAR with some assumptions made.
RE: Start Capacitor sizing
For operation at 110 Volts, the power line 1 (L1) is connected to T1,T3and T8.
Line 2 (L2) to T2,T4 and T5.
For optimum torque, test the capacitor voltage drop and the starting winding voltage drop when the rotor is locked.
The capacitor voltage drop must be 5 to 10 % larger than the starting winding voltage drop.