Capacitor run motor:
There is no switch in the starting winding and capacitor is permanently connected.
Starting torque is lower about 50 to 100% of full load torque.
Capacitor start and capacitor run Motor:
Two capacitors are used. One for starting and the other for running purpose. These motors give best performance in terms of efficiency and power factor.
2. Shaded pole motor:
Each shaded pole has its own exciting coil. About 1/3 rd portion of each pole core is surrounded, by a strap of copper forming a shading coil. When the flux is increasing in the pole, a portion of the flux attempts to pass through the shaded tip or shaded portion of the pole. This flux induces voltage and hence current in the copper ring, and by Lenz's law the direction of current is such that it opposes the flux entering the coil. Hence in the beginning, the greater portion of the flux passes through un shaded side of each pole. When the flux reaches its maximum value, its rate of change is zero thereby the e.m.f. and hence current in the shading coil becomes zero. Large amount of main flux then links with the coil. After the main flux tends to decrease, the current induced in the shading coil now tends to prevent the flux linking with shading coil from decreasing. The shading coils thus causes the flux in shaded portion as shown to lag the flux in shaded portion of the pole.
Speed torque characteristics is shown here starting torque is very small about 50% of full load torque.
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