1
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Describe the function of the Inverter.
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Function
of the Inverter
- The function
of the inverter is to convert fixed DC into variable voltage, variable
frequency alternating supply.
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2
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Explain the term : DC link converter
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DC
link converter
- It is a
combination of the AC to DC converter and DC to AC converter. The input and
output stage is AC whereas the intermediate stage is DC.
- The DC link
converter consists of rectifier at the input stage and inverter at the output
stage.
- It is a two stage static frequency converter in which the alternating
power at source frequency is rectified and filtered.
- The output of the
rectifier is fed to the input of the inverter which convert fixed DC into
variable voltage, variable frequency alternating supply.
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3
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What should be input of the inverter?
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It may be DC
source, battery, fuel cell, solar cell or rectifier.
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4
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Which semi conductor device is used in the inverter circuit
for the high power output?
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Silicon
controlled rectifier ( SCR )
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5
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Which semi conductor device is used in the inverter circuit
for the low power output?
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Semiconductor
Devices
- Bi –
junction transistor ( BJT )
- Gate turn off
thyristor ( GTO )
- MOS controlled
thyristor ( MCT )
- Metal oxide
field effect transistor ( MOSFET )
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6
|
Which type of wave shape the output voltage of the ideal
inverter consists of?
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Sinusoidal
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7
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On which factor the output frequency of the inverter depends?
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Switching time
of the semiconductor device
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8
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Describe the different types of the inverter.
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Types
of inverter
According to
output supply
According to
input source
- Voltage source
- Current source
According to
output waveform
- Square wave
- Pulse width
modulation
- Quasi square
wave
According to
commutating components connections
Bridge
inverter : Half bridge and Full bridge
According to
method of commutation
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9
|
What is meaning of the forced commutated inverter and line
commutated inverter?
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Forced
commutated inverter
- The inverter
in which the SCR turns off by naturally zero is called as the naturally
commutated inverter.
Line
commutated inverter
- The inverter
in which the SCR turns off by forced commutation is called as the forced
commutation inverter.
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10
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How many switching semiconductor devices are used in the
single phase half bridge inverter?
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Two
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11
|
Explain the term : Cross conduction or shoot – through –
fault
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Cross
conduction ( shoot – through – fault )
- The single
phase half bridge inverter in which incoming and outgoing semiconductor
switches conduct simultaneously for a short time is called as cross
conduction or shoot – through – fault.
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12
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Describe the effect of shoot – through – fault effect.
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Effect
of shoot – through – fault
- The DC input
supply is short circuited and both switching semiconductors are damaged.
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13
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How the cross conduction of the semi – conductor device is
avoided?
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Cross
conduction
- The cross
conduction of the semi – conductor device is avoided by dead band or delay is
introduced between the trailing edge of the base drive of the outgoing semi – conductor device and
leading edge of the base drive of the incoming semi – conductor device.
- The dead band should be longer time than
that of the turn off time of the switching semiconductor devices.
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14
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How many switching semi – conductor devices conducts during
dead band in the single phase half bridge inverter?
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Not a single
semi – conductor
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15
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How many switching semiconductor devices are used in the
single phase full bridge inverter?
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Four
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16
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What is meaning of the voltage source inverter and current
source inverter?
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Voltage
source inverter
- It is inverter
in which the output voltage remains constant for a given type of load.
- The
large capacitor is connected at the input side of the inverter.
Current
source inverter
- It is inverter
in which the input current remains constant for a given type of load.
- The
large inductor is connected in series with the supply source at the input
side.
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17
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Describe the different method of voltage control of the single
phase inverter.
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Method
of voltage control
External
control
- AC output
voltage
- DC input
voltage
Internal
control
Pulse width
modulation ( PWM ) control
- Single PWM
- Multiple
PWM
- Sinusoidal
PWM
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18
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What is meaning of the pulse width modulation technique?
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Pulse
width modulation
- It is
technique in which the on and off time of the switching semiconductor is
varied.
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19
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Describe the advantages and disadvantages of the PWM
techniques.
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Advantages
- The output
voltage can be control without any external components.
- Lower order harmonics
are eliminated therefore the filter requirement is minimized whereas the
higher order harmonics are easily filtered.
Disadvantages
- The inverter
grade SCRs requires which have low turn on and turn off time.
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