Embed Size (px)
Citation preview
AC MachinesLecturer
SYARIFFUDDIN MAHMUDSYAH
1 Phase Induction Motors
• 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
At the end of this section you will be able to:
TypesSquirrel Cage • Split phase
• Capacitor start
• Capacitor start Capacitor run
• Permanent split phase capacitor run
• Shaded Pole
Wound Rotor • Series universal
• Repulsion
Construction
Construction1. Low resistance
2. High XL
3. Set deeper in laminations to increase XL
Run or Main Windings
Start or Auxiliary Windings1. High resistance (thinner wire)
2. Low XL (fewer turns)
3. Set shallower in laminations to limit XL
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
Split Phase Motor Construction
High resistance
Low XL
Low resistance
High XL
Switch opens ≈ 70 – 80% full load speed
Split Phase Motor Construction
Low resistance
High resistance
Split Phase Motor Construction
Capacitor Start Motor
Electrical Characteristics
IR
IS
IRef
Split Phase
Capacitor Start
Torque = K IR IS sinα
α = Angle between IR and IS
K = constant
Construction
Construction
Shaded Pole
Shaded Pole
Shaded Pole
Shaded Pole
Shaded Pole
Reluctance Motor
• Low efficiency
• Low torque
• Constant Speed
• Fractional sizes
1Φ Synchronous Machine
Reluctance Motor
Same as: Split phase
or
Capacitor Start Motor
Stator
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
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
Reluctance MotorIf rotor poles are a multiple of the stator poles
Motor will operate at sub-multiples of synchronous speed
Hysteresis MotorRotor
• Outer section made up of hardened steel
Hysteresis MotorRotor
• Outer section made up of hardened steel
• This outer section supported on the shaft by a NON-MAGNETIC “Arbour”
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
Universal Motor
Not the same as a series DC Motor
Fields are laminated for AC current
Universal Motor
Universal Motor
