Single Phase Motors

Course Number: 727.1

Covers the types and operating principles of common single-phase motors. Explains NEMA motor standards. Explains how to identify motor leads on split-phase, capacitor-start, capacitor-run, permanent split capacitor, and repulsion motors. Also covers universal motors, shaded-pole motors, and other special types, including synchro and servo systems. Gives general maintenance procedures on all single-phase motors.

Recommended Contact Hours - 15

Chapter 1: Introduction to Single-Phase Motors

Topics: Motor parts; NEMA motor standards and enclosures; Nameplate data; Induction motors; Stator, rotor field; Split-phase starting; Synchronous speed; Starting switches

Learning Objectives:

• List the parts of a rotor.
• List the data given on a typical motor nameplate.
• Explain how an induction motor works.
• Demonstrate how to calculate the number of electrical degrees in one complete rotation of a motor.
• Explain how a centrifugal switch works.

Chapter 2: Split-Phase Motors

Topics: Motor connections; Skein and consequent-pole windings; Two-speed, three-, four-winding, and dual-voltage motors; Troubleshooting

Learning Objectives:

• State the reason why a second stator winding is important in the single-phase induction motor.
• Explain how to identify motor leads when there are no tags or colors to identify them.
• Describe a skein winding.
• List the ways to change the speed of a motor by changing the number of poles.
• Discuss some common motor problems.

Chapter 3: Capacitor Motors

Topics: Kinds and operation; Rotating magnetic fields; Single-voltage, dual-voltage, reversible, capacitor-start, and capacitor-run motors

Learning Objectives:

• State the definition of a capacitor.
• Explain how to make a split-phase motor operate as a capacitor-start motor.
• Explain how the running windings are connected to make a dual-voltage motor run on either 120 or 240 volts.
• Select the best capacitor to use as a substitute for a defective capacitor when an identical unit is not available.
• List problems that cause the circuit breaker to trip when you turn on a capacitor motor.

Chapter 4: Repulsion Motors

Topics: Repulsion principle; Purpose of brushes; Short circuiter; Commutator; Repulsion, compensated repulsion, and repulsion-induction motors

Learning Objectives:

• Discuss the operating principles of a repulsion-start induction-run motor.
• Explain how to seat new brushes on the commutator.
• Discuss the functions of the major motor components.
• List the reasons a repulsion motor might fail to start.

Chapter 5: Universal Motors

Topics: Performance characteristics; Speed control; Motor life; Universal motor assemblies; Ventilation; Brush mounting and selection

Learning Objectives:

• Explain eddy current loss in the universal motor.
• List the advantages of a universal motor.
• Explain how the speed of the universal motor is controlled.
• List the criteria for selecting carbon brushes for universal motors.
• State reasons why a universal motor might have poor torque.

Chapter 6: Special Motors

Topics: Shaded-pole, synchronous, hysteresis, unexcited synchronous, induction, reluctance, and permanent-magnet motors

Learning Objectives:

• State the definition of a salient pole.
• Explain the operating principles of a shaded-pole motor.
• Discuss the operating principles of a hysteresis motor.
• Explain the difference between an unexcited synchronous motor and an excited synchronous motor.

Chapter 7: Synchros

Topics: Rotor and stator construction; Synchro assembly and transmitter operation; Receivers; Control synchro systems; Control transformer

Learning Objectives:

• State the definition of the term synchro.
• Describe motor construction in a synchro.
• Demonstrate how to calculate terminal-to-terminal stator voltage.
• State the reason why the control transformer is important in a synchro control system.
• Explain how to connect a differential synchro system.

Chapter 8: Servos

Topics: Servomechanisms; Amplidyne operation; Overtravel control; DC and AC servomotors; Servo-control bridges; Servo actuators

Learning Objectives:

• State the definition of a servomechanism.
• List the four characteristics needed to keep a regulated quantity matched to a reference valve in a servomechanism.
• Explain how an amplidyne control system works.
• Discuss how to control overtravel in a servomechanism.

Chapter 9: Motor Installation

Topics: Conductor size; Preventing shorts and grounds; Controllers; Overcurrent protection; Guards; Grounding; Fuses; Starters; Service factor

Learning Objectives:

• Explain how to determine conductor size for motors.
• State the definition of a controller.
• List the conditions under which the frames of stationary motors must be grounded.
• Demonstrate how to determine the size of a dual-element when two or more motors are connected to one feeder.
• List the electrical and mechanical factors to consider in selecting a motor for a specific application.

Chapter 10: Motor Maintenance

Topics: Procedures; Testing capacitors and stator windings; Armature defects; Noisy operation; Bearing problems; High temperatures; Incorrect speed

Learning Objectives:

• Demonstrate how to test bearings for wear.
• Explain how to test capacitors.
• State the reason why proper belt tension in important.
• List the common causes of excessive brush sparking.