ESHAN COLLEGE OF ENGINEERING FARAH, MATHURA

SEMINAR PRESENTATION

ON 3-PHASE INDUCTION MOTOR

Submitted to-: Submitted by-: Er.Mayank jain Pawan kumar B.Tech EE(3rd Year) Roll no.1347120006

Contents• Introduction• Construction• Parts of induction motor• Rotor construction• Rotating magnetic field(RMF)• Principle of operation• Equivalent circuit• Power losses• Power flow in induction motor• Torque speed characteristics• Speed control• Advantage• Application.

Introduction

• Induction Motors transform electrical energy into mechanical energy. – simple design, Cheap,robust, low-price, easy

maintenance.– wide range of power ratings: fraction

horsepower to 10 MW – run essentially as constant speed from no-load

to full load.– Its speed depends on the frequency of the

power source.

Construction

• The three basic parts of an Induction motor are the rotor, stator, and enclosure.

• The stator and the rotor are electrical circuits that perform as electromagnets.

Parts of induction motor

Rotor construction

• The rotor is the rotating part of the electromagnetic circuit.

• It can be found in two types:– Squirrel cage–Wound rotor

• However, the most common type of rotor is the “squirrel cage” rotor.

Fig.1.Squirrel cage rotor Fig.2.Wound rotor

Rotating magnetic field

• When a 3 phase stator winding is connected to a 3 phase voltage supply, 3 phase current will flow in the windings, which also will induced 3 phase flux in the stator.

• These flux will rotate at a speed called a synchronous speed, ns. The flux is called as rotating magnetic field

• Synchronous speed: speed of rotating flux

pfns

120

Principle of operation

• When a 3 phase stator winding is connected to a 3 phase voltage supply, 3 phase current will flow in the windings, hence the stator is energized.

• A rotating flux φ is produced in the air gap. The flux Φ induces a voltage ea in the rotor winding (like a transformer).

• The induced voltage produces rotor current, if rotor circuit is closed.

• The rotor current interacts with the flux φ, producing torque. The rotor rotates in the direction of the rotating flux.

Equivalent Circuit

Power losses

• Copper losses– Copper loss in the stator (PSCL) = I12R1– Copper loss in the rotor (PRCL) = I22R2

• Core loss (Pcore)• Mechanical power loss due to friction and wind age.

Power flow in induction motor

Torque-speed characteristics

Speed Control

There are 3 types of speed control of 3 phase induction machines

i. Varying rotor resistance.ii. Varying supply Frequency.iii. Stator voltage control.

Advantage

• Low cost.• High starting torque.• Maintenance easily.• Induction motor can be operated in polluted and

explosive environments.• Induction motor are simple and robust in construction.

Application

• Water pump.• Lathe machine• Printing machine• Grinding machine.

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