The Schrage Motor, Model 8234, is a variable-speed
polyphase AC motor with both high torque and efficiency.
It requires standard three-phase power.
The Schrage Motor is used in a variety of industrial
applications, such as packaging machinery, conveyors,
pumps, and knitting machines, where full torque is needed
over a variable speed range. The motor is basically
a special wound-rotor motor in which a built-in
variablefrequency
source is connected to one winding, while the
network frequency is applied to the other winding. The
voltage of the variable frequency source can be set over
a certain range and the resulting speed of the motor
depends upon this setting.
The Schrage Motor circuit diagram pictured in
Figure 1 shows that the primary winding is on the rotor
and the insulated secondary winding is on the stator. On
the rotor, there is a tertiary, or control, winding, which
is
connected to the secondary windings on the stator via
a commutator and three pairs of adjustable brushes
lying on the commutator. When the brushes in each pair
move apart or closer together, a variable voltage is
applied to the secondary winding by the tertiary winding.
The change in voltage varies the speed of the motor
below and above synchronous speed.
