1
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Describe the different types of Permanent magnet synchronous
motor.
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The Permanent
magnet synchronous motor is classified as below
- Permanent
magnet synchronous motor ( BLAC )( Sinusoidal waveforms )
- PM Brushless
DC motor ( BLDC )( Trapezoidal waveform )
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2
|
Which are the main
parts of the BLDC motor?
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Stator
- It consists of
winding similar to DC motor armature.
Rotor
- It is made of
permanent magnet.
Hall
sensors
- They are
embedded in the stator on the non – driving end of the motor to sense the
position of the rotor.
- When the rotor
magnetic pole pass near the hall sensors, they give high or low signal
indicates that the N or S pole passes near the sensors.
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3
|
Give the reason
behind the name of ‘ BLDC ’ motor.
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The BLDC motor
has straight line speed torque characteristics similar to that of permanent
magnet direct current motor so it is called as BLDC motor.
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4
|
Compare the
sinusoidal winding and trapezoidal winding in the BLDC motor.
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Sinusoidal
and trapezoidal winding
- The torque
output of the sinusoidal winding is smoother than the trapezoidal winding.
- The sinusoidal
winding requires extra winding interconnection which increases the weight and
cost of copper stator winding.
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5
|
Give the examples of
rare earth alloys.
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Rare
earth alloy magnet
- Samarium cobalt
- Neodymium
- Alloy of
neodymium, ferrite and boron
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6
|
Compare rare earth
alloy magnet and ferrite magnet.
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Ferrite
magnet
- Low flux
density per unit volume
- Less costly
Rare
earth alloy magnet
- High flux
density per unit volume
- Costly
- High torque as
compare to ferrite magnet for same size
- Improved size
to weight ratio
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7
|
State the
configuration of the BLDC motor.
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According of Construction of BLDC motor, it is configured as
- Outer rotor
motor
- Inner rotor
motor
- Special
configuration motor
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8
|
Compare outer rotor
and inner rotor BLDC motor.
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Outer
rotor BLDC motor
- High rotor
inertia is necessary
- The outer
rotor motor has much more magnetic material than the inner rotor motor
- Application :
computer disk, drives, cooling fans
Inner
rotor BLDC motor
- Lower inertia
because of small rotor diameter
- Accelerate
more rapidly due to small rotor diameter
- Most of the
inner rotor BLDC motor has multiple phase in order to reduce starting
problems
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9
|
Is there cogging
problem in the slot less brushless inner rotor BLDC motor?
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Cogging
Problem
- The stator of
the inner rotor BLDC motor has no teeth therefore there is no variation of
permeance as the rotor moves resulting no cogging problem.
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10
|
How the sensing of
the rotor position is done in the stepper motor?
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Stepper
Motor – Rotor Position
- The rotor
position of the stepper motor is sensed by placing three sensors in the
stator on the non – driving end.
- Whenever the
rotor magnetic poles pass near the hall sensors, they produce either LOW or
HIGH signal which indicates either N or S pole passing near the hall sensors.
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