Modified series Inverter
The capacitor supply 50% of the load current and the DC source supply 50% of the total load current therefore the load current is drawn not only form the supply source but also from the capacitor in the modified series inverter.
Which semiconductor
switching device is used in the high frequency series inverter?
Inverter grade thyristors
What is meaning of the time-sharing
principle in the series inverter?
Time sharing Principle
The inverter can be operated at high frequency by
using time sharing principle. The numbers of series inverters are operated in
parallel in the time-sharing inverter.
What is reason behind the
name ‘Parallel’ inverter?
Parallel inverter
As the commutating capacitor is connected parallel to
the supply source, it is called as parallel inverter.
Whether the output waveform
of the parallel inverter is sinusoidal?
The output waveform of the parallel inverter is square
wave.
Describe the function of
the feedback diodes in the parallel inverter.
Function of feedback diodes
The function of the feedback diodes is to permit load
reactive power fed back to the DC supply when the load is inductive.
Give reason : The feedback
diodes are connected to midpoint instead of end point of the transformer
winding in the parallel inverter
Feedback diodes connection
If the feedback diodes are connected to the end points
of the transformer, the commutating energy is dissipated in the SCRs and diodes
therefore the de – rating of the SCRs and diodes is done. The efficiency of the
parallel inverter can be increased by connecting feedback diodes to mid-tap
points.
Describe the advantages and
disadvantages of the Parallel inverter
Advantages
It is possible to generated sinusoidal waveform by
using suitable filters. Simple forced commutation circuit
Disadvantages
It is useful only when load is constant.
Design for fixed voltage
The inverter is not useful for high power if the value
of inductor and capacitor is fixed.
What is meaning of the 180-degree
mode of inverter operation?
180 Mode Inverter Operation
The 180-degree operation of the inverter signifies
that each semiconductor switch conducts for 180 degrees.
When gate signal is applied
in the 180 degree and 120-degree operation of the inverter?
The gate signal applied and removed for 60-degree
interval of the output waveform in the 180 degree and 120-degree operation of
the inverter.
How many semiconductor
switches conduct at a time in the 180-degree operation of the inverter?
Three ( one from each leg or two from any one leg and
one from other leg )
What is phase shift between
two adjacent switches in the 180-degree operation of the inverter?
60 degrees
What is meaning of the 120-degree
mode of inverter operation?
120 Mode Inverter Operation
The 120-degree operation of the inverter signifies
that each semiconductor switch conducts for 120 degrees.
How many semiconductor
switches conduct at a time in the 120-degree operation of the inverter?
Two ( one from positive
leg and other from negative leg )
What is phase shift between
two adjacent switches in the 120-degree operation of the inverter?
60 degrees
Describe the main
difference between 180 degree and 120-degree mode of operation in the inverter.
180-degree operation of inverter
Each semiconductor switch conducts for 180-degree
operation.
Two switches are conducted from positive leg whereas
one switches from negative leg and vice versa.
The rated output power of the inverter is 33.3% of the
maximum power rating of the six semiconductor switches.
120-degree operation of inverter
Each semiconductor switch conducts for 180-degree
operation.
One switch conducts from positive leg and one switch
from negative leg.
The rated output power of the inverter is 28.9% of the maximum power rating of the six semiconductor switches.
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