Three Phase Full Converters MCQ Quiz in বাংলা - Objective Question with Answer for Three Phase Full Converters - বিনামূল্যে ডাউনলোড করুন [PDF]
Last updated on Mar 18, 2025
Latest Three Phase Full Converters MCQ Objective Questions
Top Three Phase Full Converters MCQ Objective Questions
Three Phase Full Converters Question 1:
A three phase fully controlled bridge converter is feeding a load drawing a constant and ripple free load current of 20 A at a firing angle of 60°. The approximate total harmonic distortion (% THD) and the rms value of fundamental component of input current will respectively
Answer (Detailed Solution Below)
Three Phase Full Converters Question 1 Detailed Solution
Total rms current
Fundamental current
Three Phase Full Converters Question 2:
A solar energy installation rectifier a three phase bridge converter to load energy into power system through a transformer of 400V/ 400V, as shown below.
The energy is collected on a bank of 400V battery and is connected to converter through a large filter choke of resistance 10Ω.The KVA rating of the output transformer is
Answer (Detailed Solution Below)
Three Phase Full Converters Question 2 Detailed Solution
Input transformer kVA rating =
kVA rating of transformer
= 22.6kVA
Three Phase Full Converters Question 3:
Compute the peak inverse voltage of thyristor connected in three-phase, six-pulse bridge rectifier having input voltage of 415 V. Consider the voltage safety factor to be 2.1.
Answer (Detailed Solution Below)
Three Phase Full Converters Question 3 Detailed Solution
The Correct option is 3
Concept:
The output voltage of 3 phase 6 pulse bridge rectifiers is:
VO =
Rms Line voltage = 415 V
Out voltage = VO
Calculation:
Pick inverse voltage 3 phase 6 pulse bridge rectifiers if the safety factor is 2
V peak =
Peak inverse voltage =Vpeak
Additional Information Thyristor:
- A thyristor is a four-layer semiconductor device, consisting of alternating P-type and N-type materials (PNPN). A thyristor usually has three electrodes: an anode, a cathode, and a gate, also known as a control electrode.
Three Phase Full Converters Question 4:
In a single-phase full-wave bridge circuit and in a three-phase, delta full-wave bridge circuit, what will be the ripple voltage frequency respectively?
Answer (Detailed Solution Below)
Three Phase Full Converters Question 4 Detailed Solution
Concept:
Ripple frequency of three-phase full-wave converter:
Figure: output voltage waveform of three-phase full-wave rectifier.
From the above output voltage waveform, we can observe that for a complete one cycle of input supply we got 6 pulses in the output.
So, the three-phase full-wave ac to dc converter is a 6-pulse converter.
Then the ripple frequency of the output f0 = m × f
Where,
m = number of pulses in the output per one complete cycle of the input
f = supply voltage frequency
Solution:
For single-phase full-wave bridge circuit f0 = 2 × f
For a three-phase full-wave converter f0 = 6 × f
Hence, the ratio output ripple-frequency to the supply-voltage frequency = f0 / f = 6
Three Phase Full Converters Question 5:
A six pulse thyristor bridge converter is connected to a balanced three-phase Ac source. Assuming that the DC current of the rectifier is constant.
Which of the following harmonic components are absent in the AC input current.
Answer (Detailed Solution Below)
Three Phase Full Converters Question 5 Detailed Solution
In a six-pulse thyristor bridge converter, the harmonics present in source or current are:
6k ± 1, k = 1, 2, 3 …
So, the harmonics present are 5, 7, 11, 13…
Harmonics frequencies are 250 Hz, 350 Hz, 550 Hz, 650 Hz…
Therefore among the given options, only 250 Hz is present.
Three Phase Full Converters Question 6:
How many thyristors are there in a three-phase full wave controller?
Answer (Detailed Solution Below)
Three Phase Full Converters Question 6 Detailed Solution
Three-Phase Full Converters:
If all diode is replaced by thyristor, a three-phase full converter bridge formed as shown below,
- A three-phase input supply is connected to the terminal A, B, C, and RLE load is connected across the output terminal.
- It worked as three-phase AC to DC converter for firing angle delay 0
- The positive group of SCRs is fired at an interval of 120° and a similarly negative group of SCRs fired at an interval of 120°, but SCR of both groups are fired at an internal of 60° or commutation occurs at every 60°.
- At any time tow SCRs, one from the positive group and one from the negative group must be conducted together for the source to energize the load.
Waveform:
Voltage and Current Equation:
The average output voltage (V0) is given by,
Where Vm is the maximum value of line voltage.
Voltage and current waveform for α = 30° and for constant current can be drawn as,
From waveform RMS value of Thyristor current (IT = iT1) will be,
Where I0 is constant DC load current.
Three Phase Full Converters Question 7:
A 3-ϕ fully controlled converter is fed through the star-delta transformer as shown in the figure
The converter is operated at a firing angle of 300. Assuming the load current (Io) to be virtually constant at 1 p.u. and the transformer to be an ideal one, the input phase current waveform is
Answer (Detailed Solution Below)
Three Phase Full Converters Question 7 Detailed Solution
Assuming each secondary winding is identical and has the same resistance R
When the R phase has a maximum voltage, lines a and c will conduct. At this condition, the current will be divided into R and YB winding.
Current through
Current through B and Y =
And
Current through R and Y
Current through B
The current through Δ-phase winding
Current through primary
Three Phase Full Converters Question 8:
A solar energy installation rectifier a three phase bridge converter to load energy into power system through a transformer of 400V/ 400V, as shown below.
The energy is collected on a bank of 400V battery and is connected to converter through a large filter choke of resistance 10Ω.The maximum current through the battery will be
Answer (Detailed Solution Below)
Three Phase Full Converters Question 8 Detailed Solution
Three Phase Full Converters Question 9:
A three-phase diode bridge rectifier supplied from a three-phase, 400 V, 50 Hz ac supply delivers power to a resistive load of 50 Ω. The peak value of the instantaneous load voltage would be
Answer (Detailed Solution Below)
Three Phase Full Converters Question 9 Detailed Solution
As the load is resistive the peak instantaneous output voltage is
Vm = √2 Vrms
Three Phase Full Converters Question 10:
A three phase converter feeds pure resistance load at a firing angle of α = 60°. The average value of current flowing in the loads is 10 A. If a very large inductance is connected in the load circuit, then the:
Answer (Detailed Solution Below)
Three Phase Full Converters Question 10 Detailed Solution
Given that:
There phase converter feeds purl resistive load.
Firing angle α = 60°
There phase full converter is a fully controlled bridge converter using 6 thyristors connected in the form of a full wave bridge configuration
For firing angle α = 60°,
Now, average value of current is,
For both R and RL load average current equation is same.
Therefore, its value is also same i.e. 10 A for R and RL load.