1
|
State the function of the
cycloconverter.
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|
Function
of the cycloconverter
- The function of the
cycloconverter is to convert constant voltage, constant frequency into
variable voltage, and variable frequency without any intermediate stage.
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2
|
Describe the Principle of
operation of the cycloconverter.
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|
Principle
of cycloconverter
- The cycloconverter
consists of dual converter in which one converter works as positive converter
whereas the other as the negative converter.
- The firing angle of
the both converter are adjusted such that
αp + αn = π
αp = Firing angle of
positive converter
αn = Firing angle of
negative converter
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3
|
Describe the effect on
distortion on the output frequency of the cycloconverter?
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|
As the output frequency increases, the
distortion increases and vice versa.
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4
|
Describe the different
types of cycloconverter.
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|
Types
of cycloconverter
- According
to frequency : ( 1 ) Step up cycloconverter and ( 2 ) Step
down cycloconverter
- According
to output voltage : ( 1 ) Single phase to single phase –
( a ) Centre taped cycloconverter and ( b ) Bridge configuration
cycloconverter ( 2 ) Single phase to three phase ( 3 ) Three phase to three
phase
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5
|
Whether the cycloconverter
is Phase commutated?
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|
All types of cycloconverters are phase
commutated except step up cycloconverter. The step up cycloconverter is
forced commutated.
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6
|
What is advantage of
bridge configuration cycloconverter over centre taped cycloconverter?
|
|
The centre taped transformer is not
requires in the bridge configuration cycloconverter.
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7
|
Describe the function of
the intergroup reactor in the cycloconverter?
|
|
Function
of the intergroup reactor
- The intergroup
reactor is connected between midpoint of the positive converter and negative
converter.
- It protect the supply from short circuited in the case of both
converters are enabled.
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8
|
What is meaning of the blocked
mode cycloconverter?
|
|
Blocked
mode cycloconverter
- The cycloconverter
consists of positive converter and negative converter.
- When the load voltage
is positive, the positive converter operates whereas the negative converter
is disabled.
- When the load voltage is negative, the negative converter
operates whereas the positive converter is disabled.
- This is called as
blocking mode operation of the cycloconverter.
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9
|
Whether the blocking mode
cycloconverter requires any intergroup reactor?
|
|
No
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10
|
Describe the advantages
and disadvantages of blocking mode over circulating current mode cycloconverter.
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|
Advantages of blocking mode over
circulating mode
- No inter group reactor
is necessary.
- Low cost and size
- Only one converter is
in operation at all times therefore low losses and high efficiency.
Disadvantages of blocking mode over
circulating mode
- Distorting voltage
and current waveform due to delay time.
- The circulating
current mode operation has smooth load voltage and fewer harmonic.
- Harmonics in the
output waveform
- More control
complexity due to current reversal.
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11
|
Describe the advantages
and disadvantages of the cycloconverter.
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|
Advantages
- Higher efficiency due
to single stage conversion
- All the
cycloconverter works on line commutation except step up cycloconverter
therefore it is not necessary for extra commutating components.
- The power transfer
from supply to load and vice versa at any power factor.
- It can operate at
distorted output waveform in the case of one SCR gets damaged.
- It can generate high
quality sinusoidal waveform particular at low frequency whereas the static
inverter generate step wave voltage waveform at low frequency ( < 10 Hz ).
Disadvantages
- Control circuit
becomes complex due to higher number of SCRs.
- Low power factor for
low output voltage
- The supply should be
short circuited due to failure of commutation circuit.
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12
|
State the applications of
the cycloconverter.
|
|
Applications
of the cycloconverter
- Speed control of AC
drives
- Grinding mill drives
- Induction heating
- Variable frequency
supply for shipyard or aircraft
- Static VAr generation
- HVDC transmission
line
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13
|
What is meaning of the
hybrid operation of cycloconverter?
|
|
Hybrid
operation
- When the
cycloconverter operates on both blocking as well as circulating current mode,
it is called as hybrid operation.
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