8.3. Induction (Asynchronous) Machines 107
will search out the initial rotor position by applying a small field exci-
tation and observing the induced voltages in the stator phase wind-
ings. The drive phase can then be adjusted so that there is no torque
transient or reverse rotation on starting.
Modern variable-frequency drives have enabled synchronous
motors to replace many of the large DC machines used in steel mills
for rapid reversing because of their ability to provide transient torques
of several times rated value. The drive must be able to determine the
torque angle and maintain a safe margin from pole slipping.
8.3. Induction (Asynchronous) Machines
The stator winding for an induction machine looks like the stator
winding on a synchronous ...