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HIGHLIGHTS

1.   There are two basic types of single-phase induction motors which start on the split-phase principle, namely resistance-start induction-run motor and the capacitor-start induction-run motor.
2.   The resistance-start induction-run motor has a relatively poor starting torque because the phase angle between the running winding current and the starting winding current is only from 30 to 50 electrical degrees.
3.   The capacitor-start induction-run motor has a relatively good starting torque because the phase angle between the running winding current and the starting current is practically 90 electrical degrees.
4.   The capacitor- start, capacitor-run induction motor has relatively good starting torque and operates at a comparatively high power factor. The main winding and auxiliary winding are hath energized at 0/1 times the motor is in operation.
5.   A resistance-start induction-run motor or a capacitor-start induction-run motor may he reversed by interchanging the leads of the starting winding circuit. The direction of rotation of either type of motor call also be reversed by interchanging the leads of the running winding circuit. However, never attempt to change the rotation of either type of motor by reversing the line wires.
6.   The repulsion motor operates on the repulsion principles at all times. It has excellent starting torque and a relatively wide range of speeds.
7.   The repulsion-start induction-run motor starts as a repulsion motor and after it reaches 75 per cent of rated speed, operates as an induction motor. It has excellent starting torque and very good speed regulation.
8.   There are two types of brush mechanism used with repulsion-start induction-run motors: The brush-lifting type and brush-lifting type.
9.   To change the direction of rotation of either a repulsion motor or a repulsion-start induction-run motor, move the brushes to the other side of stator field poles so that there is an angle of 15 electrical degrees in the new position between the brushes and the stator field pole centres.
10.                The A.C. series motor has excellent starting torque and can be used in those applications requiring difference speeds. It has characteristics comparable to those of the D. C. series motor.
11.                The direction of rotation of an A. C. series motor can be reversed by interchanging the connections to the armature.
12.                The shaded-pole induction motor is usually made in fractional horsepower sizes in excess of 1/10 horsepower. This type of motor has no centrifugal starting device or mechanism which requires maintenance. However, the starting torque for this type of motor is small.
13.                A stepper motor is an incremental motion machine. It does not rotate continuously as a conventional motor does.
14.                The stepper motor is used in digitally controlled position control system in open loop mode.
15.                Various types of stepper motors are:
(i)                           Permanent-magnet stepper motor;
(ii)                        Variable-reluctance stepper motor;
(iii)                      Hybrid stepper motor.
16. D.C. servo-motors are preferred for very high power systems.
17. A.C. servo-motors are best suited for low power applications.