11
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Describe the construction difference between
DC motor and BLDC motor.
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DC Motor – BLDC Motor
- The rotor winding
must be eliminated from the DC motor in order to make it brush less motor.
- This can be done by
turning the DC motor inside out, it means that the winding placed on the
stator and permanent magnet on the rotor.
- The current reversal
in the BLDC motor is automatically possible by using electronic switch
instead of commutator and brushes.
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12
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Whether the BLDC motor is operated on DC
supply or AC supply?
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BLDC Motor
- The BLDC motor cannot
be driven directly by the direct current.
- The current in the
external circuit must be reversed at certain rotor position.
- Therefore the
BLDC motor is actually driven by the three phase bridge inverter or AC supply.
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13
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Give reason : The number of phases in the
BLDC motor is limited.
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Number of Phases
- The BLDC motor is
available in the single phase, two phase and three phase configuration.
- There are large
numbers of coils distributed around the stator but each coil requires its own
drive circuit.
- Therefore the number
of phases in the BLDC motor is limited.
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14
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State the condition of maximum torque in the
BLDC motor. How is it possible?
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BLDC Motor – Maximum
Torque
- The torque in the
BLDC motor becomes maximum when the stator and rotor magnetic field is 900
with respect to each other.
- As the stator winding
consists of three phase winding, the stator magnetic field advances only by
600.
- The stator magnetic
field must be 900 ahead of rotor magnetic field in order to
generate constant torque.
- It is not possible to
maintain 900 torque angle but it is possible an average of 900
torque angle by working between stator magnetic field 600 and 1200.
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15
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State the advantages of Permanent magnet
synchronous motor.
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Advantages
- No brushes or slip –
rings
- No sparking
- No brush maintenance
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16
|
How many phases are energized during
commutation in the three phase BLDC motor?
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Commutation Sequence
- Each commutation
sequence has one winding is energized to positive, the other is energized to
negative and third is in non – energized or floating.
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17
|
State the advantages of BLDC motor over DC
motor and Induction motor.
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Advantages of BLDC
motor
- Fast dynamic response
- High efficiency
- Quiet operations
- High speed range
- Better torque – speed
characteristics
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18
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State the applications of the BLDC motor.
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Applications of BLDC
motor
- Constant load : Fan,
Blower, Pump
- Variable load : Compressors,
Dryers, Washers, Fuel pump control, Electronic steering control, Robotic arm
control, Gyroscope control
- Positioning control :
Torque control loop, Position loop control, Computer numeric control machine,
Process control, Conveyor control
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19
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Give reason : The PMBLDC motor is called as
Electronic commutated motor.
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Electronic Commutated
Motor
- There is no
mechanical commutator in the PMBLDC motor.
- Therefore the
function of current reversal is done by semiconductor switches with rotor
position sensor.
- The semiconductor
switch may be IGBT or MOSFET. Therefore the PM BLDC motor is called as
electronic commutated motor.
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