
Synchronous, Switched Reluctance and Brushless D.C. Drives 269
No special starter is required for the wound rotor induc-
tion motor of course, which runs up in the usual way (see
Chapter 6) before the d.c. excitation is applied. Motors
operated like this are sometimes known as 'inductosyns'.
Power factor control
If the rotor excitation is varied when the motor is running on
load, the load angle and stator current change, but the
speed, load (and hence input power) remain the same. The
power factor of the motor can therefore be adjusted by means
of the excitation. Unity power factor operation is possible
over a wide range of loads, and by usin ...