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AC Machines 6077 SA NUE 046.

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

1 AC Machines 6077 SA NUE 046

2 1 Phase Induction Motors
At the end of this section you will be able to: Identify the basic components of a 1Ø 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

3 Types Squirrel Cage Wound Rotor Split phase Capacitor start
Capacitor start Capacitor run Permanent split phase capacitor run Shaded Pole Wound Rotor Series universal Repulsion

4 Construction

5 Construction Run or Main Windings Start or Auxiliary Windings
Low resistance High XL Set deeper in laminations to increase XL Start or Auxiliary Windings High resistance (thinner wire) Low XL (fewer turns) Set shallower in laminations to limit XL

6 Electrical Characteristics
IRef IS Run Winding Large phase Angle due to high Inductance IR Start Winding Phase Angle less, as Inductance is less than run winding

7 Split Phase Motor Construction Switch opens ≈ 70 – 80% full load speed
Low resistance High XL High resistance Low XL

8 Split Phase Motor Construction Low resistance High resistance

9 Split Phase Motor Capacitor Start Motor

10 Electrical Characteristics
Capacitor Start Torque = K IR IS sinα K = constant α = Angle between IR and IS IRef IS Split Phase IR

11 Construction

12 Construction

13 Shaded Pole

14 Shaded Pole

15 Shaded Pole

16 Shaded Pole

17 Shaded Pole

18 Reluctance Motor 1Φ Synchronous Machine Low efficiency Low torque
Constant Speed Fractional sizes

19 Reluctance Motor Stator Same as: Split phase or Capacitor Start Motor

20 Reluctance Motor Rotor Same as: Squirrel cage motor BUT, with
Uneven slots cut into laminations to form Salient poles Uneven slots assist in starting Rotor Slots generally ≠ Stator Slots

21 Reluctance Motor Starting 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 Motor becomes Synchronous

22 Reluctance Motor If rotor poles are a multiple of the stator poles
Motor will operate at sub-multiples of synchronous speed

23 Hysteresis Motor Rotor Outer section made up of hardened steel

24 Hysteresis Motor Rotor Outer section made up of hardened steel
This outer section supported on the shaft by a NON-MAGNETIC “Arbour”

25 Hysteresis Motor PROBLEM Rotor has a very high Hysteresis loss
The rotor tends to become magnetised A synchronous motor is born PROBLEM Synchronous motors have ZERO START TOURQUE! A Shaded pole stator is used

26 Universal Motor Not the same as a series DC Motor
Fields are laminated for AC current

27 Universal Motor

28 Universal Motor

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