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We know that direction of a split phase motor can be reversed if the connection of one of the windings is reversed with respect to the other. In an automatic starter this can be achieved by using two contactors i.e., one for forward direction of rotation and the other for reverse direction of rotation. The […]

This type of split phase motors have two capacitors of different values in the auxiliary winding. The motors develop a high starting torque with one capacitor of a higher value and gives a quite running performance with the other capacitor of comparatively lower value. The circuit for forward / reverse operation of a two value

This type of starter uses a current relay in series with the main winding and an auto-transformer in the auxiliary winding to increase the effective value of the capacitors in the auxiliary winding circuit. The circuit has been shown in Figure. In this circuit, when contactor M is energized, a high inrush current flows through

The principle of dynamic breaking discussed earlier in connection with poly phase induction motors, also applies well to split phase motors. The procedure, as already explained, is to disconnect the stator windings from ac supply while the motor is running and instead, connect dc supply across the windings. Full wave rectifier is used to obtain

The capacitor start motors suffer from the disadvantage that they are not easily reversible due to the centrifugal switch connected in the auxiliary winding. The motor cannot be instantaneously reversed by simple control as the auxiliary winding remains disconnected till the motor comes near to zero speed. However, by proper design of the control circuit

Speed control of split phase motors (without capacitors) is obtained by either pole changing method or by using special winding arrangements. These methods will, however, increase the size of such motors and make them expensive. To obtain two speed operation of a split phase motor, the motor will have two main windings and two auxiliary

The speed of a permanently split capacitor motor can be adjusted by connecting it to a variable voltage source such as an auto-transformer. The limitation of this method is that the starting torque developed is very low, especially when the motor is started on low speed. Another limitation is that speed is sensitive to voltage

There are various methods of controlling the speed of a universal motor. A wide range of speed control is possible by inserting a rheostat in the line circuit which causes variable voltage to appear across the motor terminals resulting in reduced motor speed. Another method of speed control, not very commonly used is by brush

The construction and principle of working of a universal series motor are similar to a dc series motor. To enable the motor to work satisfactorily on ac supply also, some modifications are required in its construction. The important modification required are: (i) Field structure should be completely laminated to avoid losses due to eddy currents:

DC motors are classified into three types depending on the way their field windings are excited. Field winding connections for the three types of dc motors have been shown in Figure. Brief description of different types of dc motors are given as follows: SHUNT MOTOR In this type of motor, the field winding is connected