Single-Phase Motors

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.

Lesson 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.