A dc separately excited motor has a constant field current. The armature is fed

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Question
A dc separately excited motor has a constant field current. The armature is fed from a single phase supply through a semi-converter. When a = 0, speed is 600 rpm. If a = 90�, the speed is likely to be
Options
A. about 300 rpm
B. about 150 rpm
C. about 75 rpm
D. about zero

Correct Answer

about 300 rpm

Explanation

Average output voltage is reduced to 50% if a = 90�. Hence speed is also reduced to 50%.

More questions

2. During forward blocking state of SCR, the voltage and current respectively are
Options
A. high and high
B. low and low
C. high and low
D. low and high

3. Match the following:

	List I		List II
A.	CTFS	1.	Periodic
B.	DTFS	2.	Non-periodic
C.	CTFT
D.	DTFT

Options
A. A-2, B-1, C-2, D-2
B. A-2, B-1, C-2, D-1
C. A-1, B-2, C-2, D-2
D. A-1, B-2, C-2, D-1

4. For the system in the given figure. The transfer function C(s)/R(s) is
Options
A. G₁ + G₂ + 1
B. G₁ G₂ + 1
C. G₁ G₂ + G₂ + 1
D. G₁ G₂ + G₁ + 1

5. In a certain inverter circuit each thyristor carries 26.67 A for 60�, 13.33 A for 120� and zero A for 180� of the cycle. The rms current of thyristor is
Options
A. 20 A
B. 13.33 A
C. 6.67 A
D. 3.33 A

7. In van der walls crystals, there exists a high degree of stability of the outer electron shell.
Options
A. True
B. False

8. If ?_r' and ?_r" are the real and imaginary parts of complex dielectric constant ?_r, and ? is the loss angle. Then
Options
A.
B.
C. tan ? = ?'?"
D. tan ? = 1 - ?'

10. In a radio receiver with simple AGC
Options
A. the highest AGC voltage is produced between stations
B. the faster the AGC time constant, the more accurate the output
C. an increase in signal strength produces more AGC
D. the audio stage gain is normally controlled by AGC

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