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AC Machines 6077SA NUE 046.

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Presentation on theme: "AC Machines 6077SA NUE 046."— Presentation transcript:

1 AC Machines 6077SA NUE 046

2 3 Phase Induction Motor Construction
At the end of this section you will be able to: Identify the basic components of a 3Ø induction motor List the types of rotors used Test motor windings for suitability to connect to the supply Connect in both star and delta List the steps for dismantling it

3 3Ø Induction Motors Why are they so common in industry?
Simple in construction Only one moving part Don’t have brush gear and commutators Now with VSD technology, Variable speed Speed of machine fixed to supply frequency

4 Rotor (The bit that Rotates)
Construction Fixed Stator (stationary) Rotor (The bit that Rotates)

5 Construction Frame can be made from cast
Iron Steel Aluminium End caps/shields bolted to each end of frame

6 Drip Proof Designed for air flow into motor Not waterproof
Not suitable for flame proof atmospheres

7 Totally Enclosed No airflow between motor inside and outside atmosphere Waterproof Easier to adapt to for flame proof atmospheres

8 Open Designed for air flow into motor Not waterproof
Very rare due to OH&S considerations

9 Core Laminations Carries the stator windings
Made of silicone steel 0.3 to 0.5mm thick Insulated from one another to reduce eddy current loss

10 Stator windings 3 identical phase windings that are displaced by 120° electrical around the stator Each winding consists of series, parallel connected coils to achieve the number of poles required. 2, 4, 6, & 8 poles per phase are common Windings are generally connected in delta but can be connected in star

11 Rotors Two Main Types Wound rotor (not common) Squirrel cage
(most common)

12 Squirrel Cage Rotor

13 Squirrel Cage Rotor Aluminium Copper Copper alloy Can be Cast
Copper/Copper alloy bars inserted into the laminations and welded/brazed to shorting ring

14 Wound Rotor Slip ring Same number of poles as stator.
One end of coil is connected to a star point Other end is terminated on a slip ring Resistance is added to change the mechanical and electrical characteristics of motor.

15 Motor Terminals

16 Motor Terminals

17 Motor Terminals U V W1 V W U2

18 Motor Terminals U V W1 V W U2

19 To Make Star Connection
Motor Terminals U V W1 V W U2 To Make Star Connection

20 To Make Delta Connection
Motor Terminals U V W1 V W U2 To Make Delta Connection

21 Electrical Testing Each winding should have the same resistance
ie 1-10 Voltage between windings =400V Insulation test level =1000V IR reading no less than 1M

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