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WorksheetsPOWER ELECTRONICS AND APPLICATIONS
Total questions: 12
Worksheet time: 6mins
Once SCR starts conducting a forward current, its gate loses control over
Anode circuit current only
Anode circuit voltage only
Anode circuit voltage and current
Anode circuit voltage, current and time
In a thyristor, the magnitude of anode current will
Increase if gate current is increased
Increase if gate current is decreased
Decrease if gate current is decreased
Not change with any variation in gate current
Surge current rating of an SCR specified the maximum
Repetitive current with sine wave
Non-repetitive current with rectangular wave
Non-repetitive current with sine wave
Repetitive current with rectangular wave
For an SCR, dv/dt protection is achieved through the use of
RL in series with SCR
RC across
L in series with
RC in series with
The applied sine voltage to a SCR is VM=200V and R=10Ohm. If the gate trigger lags the ac supply by 120°, the average load current is
15/π A
5/π A
-5/π A
-15/π A
A sine voltage of 200Vrms, 50Hz is applied to an SCR through 100ohm resistor. The firing angle is 60°. Consider no voltage drop. The output voltage in rms is
89.7 V
126.7 V
166.7 V
200√2 V
The cycloconverter require natural or forced commutation as under
Natural commutation in both step-up and step down cyclo converter
Forced commutation in both step-up and step-down cyclo converter
Forced commutation in step-up cyclo converter
Forced commutation in step-down cycloconverter
A thyristor is triggered by a pulse train of 5kHz. The duty ratio is 0.4. If the allowable average power is 100W the maximum allowable gate drive power is
100√2 W
50 W
150 W
250 W
Three-phase to three-phase cycloconverter employing 18 SCRs and 36 SCRs have the same voltage and current ratings for their component thyristors. The ratio of VA rating of 36 SCR device to that of 18 SCR device is
1/2
1
2
4
The number of SCRs required for single phase to single phase cycloconverter of the mid point type and for three phase to three phase type cycloconverter are respectively
4, 6
8, 18
4, 18
4, 36
A p-type semiconductor material is doped with ____________ impurities whereas a n-type semiconductor material is doped with __________ impurities
a) acceptor, donor
b) acceptor, acceptor
c) donor, donor
d) donor, acceptor
A p-type semiconductor material is doped with ____________ impurities whereas a n-type semiconductor material is doped with __________ impurities
a) acceptor, donor
b) acceptor, acceptor
c) donor, donor
d) donor, acceptor
