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AC Machines6077 SANUE 046

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1 Phase Induction

Motors Identify the basic components of a 1 induction motor

List the types of rotors used

Test motor windings for suitability to connect to the supply

Connect in both Clockwise and counter clockwise rotation

List the steps for dismantling it

At the end of this section you will be able to:

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TypesSquirrel Cage Split phase

Capacitor start

Capacitor start Capacitor run Permanent split phase capacitor run

Shaded Pole

Wound Rotor Series universal Repulsion

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Construction

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Construction1. Low resistance

2. High XL

3. Set deeper in laminations to increase XL

Run or Main Windings

Start or Auxiliary Windings

1. High resistance (thinner wire)2. Low XL (fewer turns)

3. Set shallower in laminations to limit XL

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Electrical Characteristics

Run Winding

IR

IS

Start Winding

Large phase Angle due to high Inductance

Phase Angle less, as Inductance is less than run winding

IRef

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Split Phase Motor

Construction

High resistance

Low XL

Low resistance

High XL

Switch opens 70 80%

full load speed

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Split Phase Motor

Construction Low resistance

High resistance

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Split Phase Motor

Construction

Capacitor Start Motor

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Electrical Characteristics

IR

IS

IRef

Split Phase

Capacitor Start

Torque = K IR IS sin

= Angle between IR and IS

K = constant

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Construction

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Construction

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Shaded Pole

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Shaded Pole

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Shaded Pole

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Shaded Pole

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Shaded Pole

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Reluctance Motor

Low efficiency

Low torque Constant Speed

Fractional sizes

1 Synchronous Machine

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Reluctance Motor

Same as:Split phase

orCapacitor Start Motor

Stator

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Reluctance Motor

Same as:Squirrel cage motor

Rotor

Uneven slots cut into laminations to

form Salient poles

BUT, with

Uneven slots assist in starting

Rotor Slots generally Stator Slots

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Reluctance MotorStarting

Motor becomes Synchronous

As per induction motor with squirrel cage providing torque

Centrifugal switch operating as per normal(75%)

As motor is lightly loaded slip speed is small

Rotor salient poles become magnetised and lock with RMF

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Reluctance MotorIf rotor poles are a multiple of the stator poles

Motor will operate at sub-multiplesof synchronous speed

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Hysteresis MotorRotor

Outer section made up of hardened steel

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Hysteresis MotorRotor

Outer section made up of hardened steel

This outer section supported on the shaft by a NON-MAGNETIC Arbour

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Hysteresis Motor Rotor has a very high Hysteresis loss

The rotor tends to become magnetised

A synchronous motor is born

PROBLEMSynchronous motors have ZERO START TOURQUE!

A Shaded pole stator is used

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Universal Motor

Not the same as a series DC Motor

Fields are laminated for AC current

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Universal Motor

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Universal Motor