Starting a DC Motor

This example shows the starting of a 5 HP 240V DC motor with a three-step resistance starter.

G. Sybille (Hydro-Quebec)

Description

Induced EMF: Eo = 240-16.2*0.6 = 230.3 V

Pe = 230.3*16.2 = 3731 W = 5.0 HP

Field current: If = 240/240 =1 A

Eo = w*Laf*If ---> w = (Eo/La*If) speed w = 230.3/1.8 = 127.7 rad/s = 1220 r/min

Nominal torque: Te = Pe/w = 3731/127.7 = 29.2 N.m

(Krause et al., Reference Analysis of Electric Machinery, pp. 89-92)