3 practice sets · Page 1 of 1
The single phase fully controlled rectifier allows conversion of single phase ____________________.
DC into AC
AC into DC
AC into AC
DC into DC
Correct Answer: B — AC into DC
Explanation:
A single-phase fully controlled rectifier uses four thyristors in a full-bridge configuration to convert AC input into controlled DC output. The firing angle α determines the output voltage level, ranging from maximum positive DC at α = 0° down to zero at α = 180°.
The input voltage with resistive load of a single phase half wave controlled rectifier is 400 sin 314t. For the firing angle of 60°, the average output voltage is __________.
(\frac{300}{\pi})
(\frac{200}{\pi})
(\frac{100}{\pi})
(\frac{400}{\pi})
Correct Answer: A — (\frac{300}{\pi})
Explanation:
The average output voltage of a single-phase half-wave controlled rectifier is (V_{o(avg)} = \frac{V_m}{2\pi}(1 + \cos\alpha)). With (V_m = 400) V and (\alpha = 60°): (V_{o(avg)} = \frac{400}{2\pi}(1 + \cos 60°) = \frac{400}{2\pi} \times 1.5 = \frac{300}{\pi}).
Three statements are given below regarding the suitable choice of HVDC converter configuration:
a. Transformer utilization factor should be nearly unity.
b. Ratio of peak inverse voltage to no load DC output voltage should be as high as possible.
c. Pulse number should be high.
Identify the correct statement and choose the correct option.
a, b and c
c and b
b and a
c and a
Correct Answer: D — c and a
Explanation:
A TUF close to unity is desirable as it indicates the transformer is being used efficiently. A higher pulse number reduces DC ripple and harmonics, improving smoothing and commutation. Statement b is incorrect — the PIV to no-load DC output voltage ratio should be kept low, not high, to prevent diode breakdown.
