PERMANENT MAGNET SYNCHRONOUS PERMANENT MAGNET SYNCHRONOUS MOTOR AND ITS DRIVES MOTOR AND ITS DRIVES Presented By: Prof. B.Adhavan Assistant Professor Dept. of Electrical and Electronics Engg [PG] Email: [email protected]Mobile No: 9994869720 1 Sri Ramakrishna Engineering College (An Autonomous Co-education Institution, approved by AICTE, Re Accredited by NBA, Affiliated to Anna University Coimbatore) Vattamalaipalayam, NGGO Colony (Post) Coimbatore - 641 022, TAMILNADU. Mobile No: 9994869720
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PERMANENT MAGNET SYNCHRONOUS PERMANENT MAGNET SYNCHRONOUS MOTOR AND ITS DRIVESMOTOR AND ITS DRIVES
Permanent Magnet Synchronous Motor (PMSM) willhave the same operating and performance characteristics assynchronous machines operating at synchronous speed, asingle or polyphase source of ac supplying the armaturewindings,
CONSTRUCTION & OPERATION
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windings,
Absence of slip rings and field windings.
Parts of a Motor
1. End Bell Fastners2. Shaft Key & Keyways3. Bearing & Brushings4. End Ball Flanges5. Identification Plates5. Identification Plates6. Wire Warnish7. Commutators8. Brush Holders9. Laminations10. Conduit Connection Box11. Magnets (Ferrites)
Brushless Motor Components
Brush Type Motor Components
PMSM MOTOR TRANSVERSESECTION
STATORSTATOR Stator laminations –Axial airgap Armature windings are double layered and lap
wound.
CONSTRUCTION
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wound. Single phase or Poly phase windings –
connected in star or delta.
Synchronous machinesare classified according to their
PM flux developed is radial in interior PM flux developed is Circumferential in Transverse
•• PMs are discs shaped and magnetized axially.• Periphery of the discs extends like claws or lundell poles.• Set of equally spaced claws on each disc alternates to north and south poles.
ROTOR ConfigurationsROTOR Configurations
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PM Motor Types
Based on Wave shape of their induced emf1) Sinusoidal (PMSM)2) Trapezoidal (BLDC)
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Sinusoidal distribution of magnet flux in the air gap
Sinusoidal current waveforms Sinusoidal distribution of stator conductors.
Sinusoidal (PMSM)
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Trapezoidal (BLDC) Rectangular distribution of magnet flux in the
air gap Rectangular current waveform Concentrated stator windings.
Rotor is carrying a constant magnetic field created either by permanent magnets or current fed coils
The interaction between the rotating stator flux, and the rotor flux produces a torque which will cause the motor to rotate.
Rotor fieldA`
B
C`
AB`
C N
S
φ
Stator field
S
N
Theory of operation:
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The rotation of the rotor in this case will be at t he same exact frequency as the applied excitation to the rotor.
This is synchronous operation.
A
phaseper pair polesmotor :p
(Hz)frequency supply AC :
(r.pm) .60
:(rad/s) speedRotor
f
p
fgives
p
ω=Ω Example: a 2 poles pair synchronous motor will run at 1500 r.pm for a 50Hz AC supply frequency
How It Works
When electric current passes through a coil in a magnetic field, the magnetic force produces a torque which turns the motor.
Force in Motor:
F=ILBF=ILBF = Force
B = Magnetic Field
L = Length of Conductor
I = Current in Conductor
Torque in Motor:
T = IBA sin θA = LW
L = Length of Winding
W = Width of Winding
PRINCIPLE OF OPERATION
BLPM SNW motor carries a 3 phase winding connected to a dc
supply through an electronic commutator.
The voltage available at the input terminals of the armaturewinding
is assumed to be sinusoidally varying 3 phase balanced voltage.
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Electronic commutator acts as an ideal inverter, whose freqis
influenced by rotor speed.
Under this condition, revolving magnetic field is set up in the air
gap.
Its flux density is sine distributed.
Synchronous operation
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Synchronous operation
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Synchronous operation
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Synchronous operation
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Synchronous operation
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Synchronous operation
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Advantages of PM machines
They have high torque to inertia (lower weight). That is better dynamic performance than conventional one.
High power density. High efficiency (That is no current in the rotor means
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High efficiency (That is no current in the rotor means no copper loss) and reliability.
Avoidance of brushes and slip rings makes the machine less audible noise,
Longer life, sparkless (no fire hazard) and high speed.
Efficient heat dissipation.
Loss of flexibility of field flux control Cost permanent magnets is high They have complex control. There is a possibility of demagnetization of the
Disadvantages of PM machines
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There is a possibility of demagnetization of the rotor magnet.
If demagnetization occurs, there will be a reduction of torque production.
There is a problem of maintenance of rotor magnet.
BLDC Vs. PMSMBLDC
Synchronous machine
Fed with direct currents
Trapezoidal BEMF
PMSM
• Synchronous machine
• Fed with sinusoidal currents
• Sinusoidal BEMF
• Continuous stator flux position
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Stator Flux position commutation each 60 degrees
Only two phases ON at the same time
Torque ripple at commutations
• Continuous stator flux position variation
• Possible to have three phases ON at the same time