Induction motor

Induction motor

Single Phase Induction Motor

Single Phase Induction Motor
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The single-phase induction machine is the most
frequently used motor for refrigerators, washing
machines, clocks, drills, compressors, pumps, and so
forth.
The single-phase motor stator has a laminated iron

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core with two windings arranged perpendicularly.

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One is the main and

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The other is the auxiliary winding or starting
winding

Single Phase Induction Motor

Single Phase Induction Motor

This “single-phase”
motors are truly twophase 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 laminated
iron core

Main winding

Slots with winding
Rotor with
laminated
iron core

+
+

Bars

_
_
Starting winding

Figure 42 Single-phase
induction motor.

Ring to short
circuit the bars

Single Phase Induction Motor

Figure 10 Squirrel cage rotor

Operating principle

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
Double revolving field theory
• A single-phase ac current supplies the main
winding that produces a pulsating magnetic
field.
• Mathematically, the pulsating field could be
divided into two fields, which are rotating in
opposite directions.
• The interaction between the fields and the
current induced in the rotor bars generates
opposing torque

Single Phase Induction Motor
Main winding flux

The interaction between
the fields and the current
induced in the rotor bars
generates opposing
torque.
Under these conditions,
with only the main...