R.N.G.P.I.T, Bardoli �Electrical Engineering Department

Subject: Electrical Machine-II

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Prepared By:

Dr. Shaikh Mohammed Suhel

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Video Lecture Link: https://youtu.be/sXGAMhcWBow

Prepared By:

• Name: Dr. Shaikh Mohammed Suhel

(Assistant Professor RNGPIT, Surat)

• Former Assistant Professor in SCET, SNPIT&RC, VIT
• Qualification: PhD (Power- Electronics & Drives, NIT, Surat), M.Tech (Industrial Electronics, NIT-Surat), Gate, B.E. (Electrical Engineering., VNSGU-Surat).
• Experience: 13 Years.

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Subject: Electrical Machine-II

• This Lecture contains

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• Difference Between AC and DC Machine
• Introduction to unipolar BLDC Machine
• YouTube Video: https://youtu.be/sXGAMhcWBow

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Syllabus.

• Which motor is used in

traction application?

1. DC Series Motor
2. Induction Motor
3. BLDC Motor
4. None of the above

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• Rugged
• Cost, efficiency and reliability
• No brushes- less maintenance
• Low mech time constant
• Suitable for all location

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• Speed control (Complex)
• Starting torque
• Drive cost

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AC Machine v/s DC Machine

BLDC Motor: Construction, Principle and control

>High Power to weight ratio

>Permanent magnet Rotor

>Principle of this motor is same as synchronous motor

>Based on rotor structure BLDC motor classified into three categories

1. Projecting magnet type
2. Inset magnet type
3. Interior magnet type.

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1. Projecting magnet type
2. Inset magnet type
3. Interior magnet type.

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i

S

w₁

w₂

w₃

BLDC Motor: Principle

>Three stator phases.

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>Stator winding is wound such that it produces South poles in the inner side of the stator pole when excited.

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w₁

w₂

w₃

BLDC Motor: Principle

>Three stator phases.

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>Stator winding is wound such that it produces South poles in the inner side of the stator pole when excited

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>Permanent magnet rotor

> Step size=120

S

i

i

S

i

S

w₁

w₂

w₃

BLDC Motor: Principle

>Three stator phases.

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>Stator winding is wound such that it produces South poles in the inner side of the stator pole when excited

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>Permanent magnet rotor

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>Step size=120

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>Clockwise: W1-W2-W3

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>Anti-clockwise:W1-W3-W2

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w₁

w₂

w₃

BLDC Motor: Principle

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How and when to Excite the stator winding?

>To excite the stator winding, DC Source and electronic switches such as transistors are used.

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>When any one of the Transistor is turned on respective phases will be energized and S pole is created under that winding.

S

S

S

BLDC Motor: Principle

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When to Excite the stator windings?

>Before excitation of any winding, information of exact rotor position is required. Stator ‘S’ pole should be created after extracting the rotor pole information.

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>When photo transistor received the light generated by the LED then photo transistor gives high signal and when photo transistor not able to receive the light generated by the LED photo transistor gives low signal.

High

Low

Low

High

BLDC Motor: Principle

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When to Excite the windings?

>The photo transistor of this encoder is connected to transistor switch to excite the winding.

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>Clock-wise rotation

PT₁-T₃

PT₂-T₁

PT₃-T₂

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BLDC Motor: Principle

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When to Excite the windings?

>Clockwise rotation

PT₁-T₃

PT₂-T₁

PT₃-T₂

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>This disk has 2/3rd opaque region that is non-transparent for light and 1/3rd region is transparent region and allow the light to pass through.

BLDC Motor: Principle

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When to Excite the Rotor?

>Clock-wise rotation

PT₁-T₃

PT₂-T₁

PT₃-T₂

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BLDC Motor: Principle

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When to Excite the windings?

>Clockwise rotation

PT₁-T₃

PT₂-T₁

PT₃-T₂

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>Anti-clockwise rotation

PT₁-T₁

PT₂-T₂

PT₃-T₃

> Unidirectional Control

BLDC Motor: Torque

• Torque=K Φ₁ Φ₂ sinδ

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> Unipolar is used for low Performance application

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Thank You!