Single-Phase Motors Single-phase AC motors are as

ubiquitous as they are useful -serving as the prime power sources for a seemingly limitless array of small-horsepower applications in industry and in the home.

The main advantage of these motors is their ability to operate from a single-phase power supply

2

The single-phase induction machine is the most frequently used motor for refrigerators, washing machines, clocks, drills, compressors, pumps, and so forth.

They are designed to operate on 120 V or 240 V.

They range in capacity from fractional horsepower to several horsepower depending on the application.

Single-Phase Motors

Single-Phase Induction Motor

In general, an ac polyphase squirrel-cage motor connected to a polyphase line will develop starting torque.

A squirrel-cage motor connected to a single-phase line develops no starting torque, but having been started by some external means, it runs approximately like a polyphase motor.

Single-phase induction motors are classified in accordance with their starting methods and are usually referred to by names descriptive of these methods.

Single-Phase Induction Motor

The single-phase motor stator has a laminated iron core with two windings arranged perpendicularly One is the main

and The other is the

auxiliary winding or starting winding

Single-Phase Induction Motor

Auxiliary Windings

Two windings that are 90 apart physically and carrying currents 90 apart in phase produce a rotating magnetic field. Single-phase induction motors contain an auxiliary winding displaced by 90 electrical degrees from the main winding.

This single-phase motors are truly two-phase machines.

The motor uses a squirrel cage rotor, which has a laminated iron core with slots.

Aluminum bars are molded on the slots and short-circuited at both ends with a ring.

Stator with laminatediron core Slots with winding

Bars

Ring to shortcircuit the barsStarting winding

+

_

Main winding

Rotor withlaminatediron core+

_

Single-Phase Induction Motor

Squirrel cage rotor

Single-Phase Induction Motor

The single-phase induction motor operation can be described by two methods:

Double revolving field theory; and

Cross-field theory.

Double revolving theory is perhaps the easier of the two explanations to understand

Learn the double revolving theory only

Single-Phase Induction Motor

Single-Phase Induction Motor

Single-Phase Induction Motor

Split-Phase Induction Motor

Split-phase motors have two stator windings, a main winding (also referred to as the run winding) and an auxiliary winding (also referred to as the start winding)

The split-phase motor

Capacitor Type Motors

Capacitor-start motor

Permanent-split-capacitor motor

Shaded-Pole Induction Motors

Single-Phase MotorsSingle-Phase MotorsSingle-Phase Induction MotorSingle-Phase Induction MotorSingle-Phase Induction MotorAuxiliary WindingsSingle-Phase Induction MotorSingle-Phase Induction MotorSingle-Phase Induction MotorSingle-Phase Induction MotorSingle-Phase Induction MotorSlide Number 12Slide Number 13Slide Number 14