Arvind Electrical: Power Electronics Bit

Power Electronics Bit

In an SCR holding current is _____________ latching current.
When SCR conducts the forward voltage drop ____________volts.
The number of p-n junctions in a thyristor is _______________.
Write the relation between α & β in BJT.
What are the triggering methods of SCR?
Define firing angle?
Write formula for string efficiency?
String Efficiency for series string?
Define derating factor?
What is the requirement of maximum string efficiency?
Define finger voltage?
Define holding current?
Define latching current?
What are the turn-off methods of thyristors?
In phase-controlled rectifiers, load current depends on the__________
The average output voltage of 1-Φ full-converter bridge rectifier is __________.
In a 1-Φ half wave circuit connected with R-L load, the angle β indicates__________.
The advantage of freewheeling diode is ________.
The average value of output load voltage for 1-Φ half wave rectifier is ________.
The average output voltage for full-converter _________.
The average output voltage for semi converter___________.
For a three phase six pulse diode bridge rectifier, the average output voltage in terms of maximum value of line voltage Vm is_____________.
Each diode of a 3-Φ half wave diode rectifier conducts for____________.
Each diode of a 3-Φ, 6-pulse bridge diode rectifier conducts for___________.
In a three phase full converter, the output voltage during overlap is equal to____________.
In a three phase full converter, the six SCRs are fired at an interval of____________.
In the circulating current mode of a dual converter, ____________ is inserted between the converters 1 and 2.
The effect of source inductance is to reduce the_____________.
In a single phase full converter, the output voltage due to overlap is _____________.
The angular period over which both the incoming and outgoing SCRs are conducting together is called____________.
A dual converter using two full converters can give _______ quadrant operation.
In the case of AC voltage regulator, control range of firing angle is given as___________.
A three phase to three phase cyclo converter requires_________ SCRs. for three pulse device.
The number of thyristors required for single phase to single phase cyclo converters of the midpoint type are_________.
For a step-down chopper working at a frequency of 500 Hz and supplying a highly inductive load, when the chopper power semiconductor device is changed from ON state to OFF state, the current in the load will________.
Chopper is a power semiconductor converter, which is used for__________.
Separately excited DC motor is supplied from a fixed input DC voltage through a step-down chopper system. In which quadrant can the DC motor be operated by this system__________.
In a Jones chopper circuit, when the auxiliary thyristor-T2 is turned ON, then which condition occurs for the main thyristor-T1 by the discharge of the capacitor through T1 and T2 _____________.
Which of the class of commutation does the Jones chopper belong to____________.
In an AC chopper feeding a load, if the RMS value of output AC voltage is to be increased, then the firing angle of thyristors must be_____________.
In a single-phase half (semi)-controlled bridge inverter, the gate signals to the main thyristors are given at an interval of______________.
In a three-phase fully-controlled bridge inverter, the gate signals to the main thyristors are given at an interval of_________.
The total number of thyristors in a three-phase fully-controlled bridge inverter will be__________.
Two thyristors T1 and T2 are used in a basic series inverter circuit to supply a series R-L-C load from an input DC supply. If the time-period for oscillation of R-L-C circuit is increased, then the inverter frequency will____________.
Two thyristors T1 and T2 are used in a basic series inverter circuit to supply a series R-L-C load from an input DC supply. When both the thyristors are OFF, the load current________.
In a basic parallel inverter, two thyristors are used to switch the dc supply alternately to the two halves of the transformer primary. For this, which of the following component is used to connect the input DC source to the mid point of the transformer ____________.
In the McMurray - Bedford full-bridge inverter, total how many numbers of thyristors will be required________.
In the current limit control of a step-down chopper, when the current reaches the lower limit, what operation must be done_________.
In a step-up chopper working on a constant input DC voltage, the duty cycle must be__________, if the average value of the output DC voltage is to be decreased.
In a three-phase bridge inverter with sinusoidal PWM control, if the modulation index is increased from 0.5 to 0.8, then it results in____________ of RMS value of output AC voltage.

Power Electronics key

Greater than
1 to 1.5 volts.
3
,
i. forward voltage triggering

ii. Gate triggering.

iii. Thermal triggering.

iv.

triggering.

The angular time elapsed between the instant of starting of source voltage and the instant of gate signal.
string efficiency= Actual voltage or current in the string/ (no. of SCRs in the string*voltage or current in the string).
Derating factor =1-
Uniform distribution of voltage across SCRs is necessary.
The minimum voltage for an SCR when gate triggering is applied for conduction.
The minimum anode current below which the SCR stops conducting.
The minimum ON-state current needed to keep the SCR conducting even with the removal of triggering pulses.
i. Natural commutation