State the function of the
cycloconverter.
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.
Describe the Principle of
operation of the cycloconverter.
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 converters are adjusted such that
αp +
αn = π
αp =
Firing angle of positive converter
αn =
Firing angle of negative converter
Describe the effect on
distortion on the output frequency of the cycloconverter?
As the output frequency increases, the distortion increases and
vice versa.
Describe the different
types of cycloconverter.
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 ( 2 ) Bridge configuration cycloconverter (
2 ) Single phase to three phase ( 3 ) Three phase to three phase
Whether the cycloconverter
is phase commutated?
All types of cycloconverters are phase commutated except step up
cycloconverter. The step up cycloconverter is forced commutated.
What is advantage of bridge
configuration cycloconverter over center taped cycloconverter?
The center taped transformer is not requires in the bridge
configuration cycloconverter.
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 protects
the supply from short circuited in the case of both converters are enabled.
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.
Whether the blocking mode
cycloconverter requires any intergroup reactor?
No
Describe the advantages and
disadvantages of blocking mode over circulating current mode cycloconverter
Advantages of blocking mode over circulating mode
No intergroup 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.
Describe the advantages and
disadvantages of the cycloconverter
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.
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
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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