PERMANANT MAGNET SYNCHRONOUS MOTOR

PERMANENT MAGNET SYNCHRONOUS PERMANENT MAGNET SYNCHRONOUS MOTOR AND ITS DRIVESMOTOR AND ITS DRIVES

Presented By: Prof. B.AdhavanAssistant Professor

Dept. of Electrical and Electronics Engg [PG]

Email: adhav14@yahoo.comMobile No: 9994869720

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Sri Ramakrishna Engineering College(An Autonomous Co-education Institution, approved b y AICTE,

Re Accredited by NBA, Affiliated to Anna University Coimbatore)Vattamalaipalayam, NGGO Colony (Post)

Coimbatore - 641 022, TAMILNADU.

Mobile No: 9994869720

OUTLINEOUTLINE

CONSTRUCTION & PRINCIPLE OF OPERATION OF CONSTRUCTION & PRINCIPLE OF OPERATION OF PMSMPMSM

TYPESTYPES OFOF PMSMPMSM PMSMPMSMVsVs BLDCBLDC

TORQUETORQUE--SPEEDSPEEDCHARACTERISTICSCHARACTERISTICS

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TORQUETORQUE--SPEEDSPEEDCHARACTERISTICSCHARACTERISTICS APPLICATIONSAPPLICATIONS CONTROLCONTROL METHODSMETHODS

Types of Electric Motors

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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

Rotor Configurations

Rotor Types

ROTOR

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Peripheral or Surface

Interior

Claw-pole

Transverse

ROTOR ConfigurationROTOR Configuration--PeripheralPeripheral

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PM flux developed is radial.

ROTOR ConfigurationsROTOR Configurations

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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

• No torque ripple at commutations

TORQUETORQUE--SPEED SPEED CHARACTERISTICSCHARACTERISTICS

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•Maximum torque is developed in PMSM by varying

the frequency from 0 to f0 .

•Further increase in frequency, the torque gets reduced

and goes to 0 at a frequency fd .

Washing machines Electrical power steering Industrial drive Servo drives

PMSM Motor Applications

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Servo drives Electric vehicle traction drive Automotive applications Refrigerator Air conditioning Fan

HighHigh speedspeed andand highhigh powerpower drivesdrives forfor

CompressorsCompressors

BlowersBlowers

PMSM Motor Applications

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BlowersBlowers

ConveyersConveyers

SteelSteel rollingrolling millsmills

AirAir craftcraft

PMSM DRIVE TOPOLOGY

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PMAC

& feedback

DRIVE

180°Conduction mode of 3 Phase Inverter- For PMSM 120°Conduction mode of 3 Phase Inverter-For BLDC

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180°Conduction

For this mode of operation, each device conducts 180 degrees.

The sequence of firing is: 123, 234, 345, 456, 561, 612. The gating signals are shifted from each other by 60

degrees.

Waveforms for 180 °°°° Conduction

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120° Conduction

In this mode, each transistor conducts for 120 degrees.

The sequence of firing is: 61, 12, 23, 34, 45, 56, 61.56, 61.

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Waveforms for 120 °°°° Conduction

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FEEDBACK SENSORS

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PMSM Motor Control

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SCALAR CONTROL - Volt/Hertz

Scalar control is based on relationships validin steady state.

Only magnitude and frequency of voltage,current, etc. are controlled.The control is an open-loop scheme and

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The control is an open-loop scheme anddoes not use any feedback loops.

The idea is to keep stator flux constant atrated value so that the motor develops ratedtorque/ampere ratio over its entire speedrange

VECTOR CONTROL

In vector control amplitude and position of a controlled space vector is considered.

Closed loop control These relationships are valid even during

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These relationships are valid even during transients which is essential for precise torque and speed control.

Types – Field Oriented Control (FOC) Direct Torque Control (DTC)

VECTOR CONTROLVECTOR CONTROL

Electromagnetic torque developed due to the interaction of the current carrying conductor and magnetic field.

CASE 1 Flux axis is in quadrature with the armature mmf axis. Angle between the axis of the flux and the

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Angle between the axis of the flux and the armature mmf axis is 90°.

Armature mmf axis

Field axis

CASE 2 Angle between the axis of the flux and the

armature mmf axis is different from 90°. For a BLDCSNW motor to have better steady state and

dynamic performance, it is essential that the armaturemmf axis and the axis of the PMare to be in quadrature inall operating conditions.

I = Id + IqI Direct axis Current

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Id Direct axis CurrentIq Quadrature axis Current

Desired operating point of current is such that Id = 0.

Controlling the BLPM SNW motor considering above mentioned aspects is known as vector control of BLPM SNW motor.

Field axis

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Armature mmf axis

SENSORED CONTROL-FOC

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SENSORLESS CONTROL-FOC

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DTC-PMSM

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THANK YOUTHANK YOU

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THANK YOUTHANK YOU