How schrage motor works?

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.