# When a line commutated converter operates in the inverter mode

1.  it draws both real and reactive power from the A.C. supply

2.  it delivers both real and reactive power of the A.C. supply

3.  it delivers real power to the A.C. supply

4.  it draws reactive power from the A.C. supply

4

it delivers real power to the A.C. supply

Explanation :
No Explanation available for this question

# In voltage source inverters

1.  load voltage waveform v0 depends on load impedance Z, where as load current wave form i0 does not depend on Z

2.  both v0, i0 depends on Z

3.  v0 does not depend on Z but i0 depends on Z

4.   none of these

4

v0 does not depend on Z but i0 depends on Z

Explanation :
No Explanation available for this question

# In an inverter with fundamental output frequency of 50 Hz, if third harmonic is eliminated, then frequencies of other components in the output voltage wave in Hz would be

1.  250, 350, 500, high frequencies

2.  50, 250, 350, 500, high frequencies

3.  50, 50, 350, 550

4.   none of these

4

50, 250, 350, 500, high frequencies

Explanation :
No Explanation available for this question

# An inverter has a periodic output voltage with the output waveform as shown in the given figure. When conduction angle α = 120o, then rms fundamental component of output voltage is

1.  0.78 V

2.  1.10 V

3.  0.90 V

4.   1.27 V

4

1.27 V

Explanation :
No Explanation available for this question

# A single-phase full-bridge voltage source inverter feeds a purely inductive load, as shown in the given figure, where T1, T2, T3, T4 are power transistors and D1, D2, D3, D4 are feedback diodes. The inverter is operated in square-wave mode with a frequency of 50 Hz. If average load current is zero, what is the time duration of conduction of each feedback diode in a cycle

1.  5 msec

2.  10 msec

3.  20 msec

4.   2.5 msec

4

2.5 msec

Explanation :
No Explanation available for this question

# An ac induction motor is used for a speed control application. It is driven from an inverter with a constant V/f control. The motor name-plate details are as follows : V = 415 V, Ph = 3, f = 50 Hz, N = 2850 rpm The motor is run with the inverter output frequency set at 40 Hz, and with half the rated slip. The running speed of the motor is

1.  2400 rpm

2.  2280 rpm

3.  2340 rpm

4.   2790 rpm

4

2340 rpm

Explanation :
No Explanation available for this question

# The speed/torque regimes in a dc motor and the control methods suitable for the same are given respectively in Group II and Group I P. Field Control 1. Below based speed Q. Armature Control 2. Above base speed 3. Above base torque 4. Below base torque The match between the control method and the speed/torque regime is

1.  P-1 ; Q-3

2.  P-2 ; Q-1

3.  P-2 ; Q-3

4.  P-1 ; Q-4

4

P-2 ; Q-1

Explanation :
No Explanation available for this question

# In machine tool drive application, the speed of separately excited dc motor is required to be controlled both below and above the rated speed of the motor. Which one of the following methods is best suited for the purpose (Vα = armature voltage, If = field current and If, rated = field current rated speed)

1.  If = If, rated, Vα variable

2.  Vα fixed, If variable

3.  Vα and If variable, with If ≤ If,rated

4.  Vα and If variable, with If ≥ If, rated

4

Vα and If variable, with If ≤ If,rated

Explanation :
No Explanation available for this question

# Consider the following statements regarding speed control of induction motors by means of external rotor resistors : Reduction in speed is accompanised by reduced efficiency. With a large resistance in the rotor circuit, the speed would vary considerably with variation in torque The method is very complicated. The disadvantage of such a method of speed control would include

1.  1 and 3

2.  2 and 3

3.  1 and 3

4.  1, 2 and 3

4

1 and 3

Explanation :
No Explanation available for this question

1.  2 RC

2.  3 RC

3.  RC/2

4.  2 RC/3

4