1
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What do you mean
by term ‘Reluctance motor’?
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Reluctance
motor
- It is an electrical
motor in which torque is produced due to position of rotor such that
inductance of the excitation winding becomes maximum.
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2
|
Describe the stator and rotor construction
of the SRM.
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Stator
: It
is salient pole type and excited by field winding.
Rotor
: It
is salient pole type.
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3
|
Give reason : The reluctance motor is also called as double salient motor.
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Double
salient motor
- The stator and rotor
of the switch reluctance motor has salient poles therefore it is also called
as double salient motor.
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4
|
State the configuration of the SRM.
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Configuration of the
SRM
- Linear SRM
- Rotary SRM : Radial
field and Axial field
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5
|
Describe the advantage and disadvantage of
shorter flux path SRM.
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Advantage
- Lower copper losses
due to flux do not reversal
Disadvantage
- Higher mutual
inductance and higher uneven magnetic pull on the rotor
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6
|
State the disadvantage of the single phase
SRM.
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Disadvantages
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7
|
On which parameter the inductance of the
stator winding depends in the SRM?
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The stator winding
inductance depends upon stator current and position of the rotor.
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8
|
Explain aligned and unaligned position of
two pole SRM.
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Aligned
- When rotor poles are
at 00 or 1800
- Maximum inductance
- Zero torque
- Magnetic circuit
likely to saturate
Unaligned
- When the rotor poles
are at 900
- Minimum inductance
- Zero torque
- Magnetic circuit does
not saturate
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9
|
Explain the torque characteristics of the
SRM.
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Torque characteristics
( Inductance – Rotor position )
- When the stator and
rotor poles do not overlap, the inductance is minimum and constant. It will
not contribute any torque.
- When the rotor poles
moves towards stator poles in aligned position, the motoring torque is
produced and the inductance is increasing.
- The movement of the
rotor poles does not alter the complete overlap of the stator pole.
- The
inductance becomes maximum and constant. It will contribute zero torque.
- When the rotor poles
moves away from the stator poles from overlapping position, the inductance
decreases and it produces negative torque.
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10
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Give reason : The ideal inductance profile
is not possible in the SRM.
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Inductance Profile
- The saturation of the
motor causes inductance profile to curve near the top and therefore reduces
the torque constant.
- The large torque
ripple produces due to rectangular current pulses. It will result in increase
audible noise, fatigue of the shaft and speed oscillations.
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11
|
How to eliminate negative torque in the SRM?
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The negative torque
in the SRM is eliminated by switching off current when the poles are
separating.
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12
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How the torque ripples can be minimized in
the SRM?
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Torque ripple
- The torque ripples
can be minimized in the SRM by designing the machine such that the inductance
profile of the two consecutive phases overlap during end of one phase and
starting of other phase.
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13
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Explain the term : stroke
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Stroke
- It is torque cycle
due to one current pulse in the SRM.
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14
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Explain the term : Phase leg
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Phase
leg
- There are two power
switches connected in series with DC source and center point of two switches
is connected to one end of the phase winding.
- This is called as
phase leg.
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15
|
Explain the term : Shoot through fault
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Shoot
through fault
- There are two power
switches connected in series with DC source and center point of two switches
is connected to one end of the phase winding.
- This is called as
phase leg.
- Only one switch is on in phase leg at any time. If the second
switch fails, it causes short circuit of the DC source.
- This type of fault is
called as shoot through fault.
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