Question

Directions: It consists of two statements, one labelled as the ‘Statement (I)’ and the other as ‘Statement (II). Examine these two statements carefully and select the answer using the codes given below:

Statement (I): For the same voltage output, the power factor of a single phase semi converter is better than a full converter.

Statement (II): The single phase semi converter uses two diodes and two controlled switches.

1. Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
2. Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)
3. Statement (I) is true but Statement (II) is false
4. Statement (I) is false but Statement (II) is true

Answer 1

Correct Answer - Option 2 : Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)

• A single phase semi converter uses two diodes and two controlled switches whereas full converter uses four controlled switches.
• For the same voltage output, the power factor of a single phase semi converter is better than a full converter because of the freewheeling action of the diode and thyristor in symmetrical connection and the freewheeling action of the two diodes in asymmetrical connection.
• It prevents the output voltage from becoming negative and hence power factor is improved.

 

Therefore, both Statement (I) and Statement (II) are individually true and Statement (II) is not the correct explanation of Statement (I).

Purpose of using Freewheeling Diode:

• The Freewheeling Diode improves the waveform of the load current of Rectifier circuits, inverter circuits, and chopper circuits by making it continuous.
• The Freewheeling protect the SCRs from damage in the circuits with Inductive Load from the excessive reverse voltage creating by the Inductive Load.
• In the converter, freewheeling diode is used to conduct current during the off period of the thyristor
• The Freewheeling Diode improves the Input Power Factor of Phase controlled Rectifiers.
• It decreases the possibility of discontinuous conduction in the load.
• The Freewheeling diode sustains the average output voltage of the circuit with an Inductive Load.
• It also helps to reduce Ripple components in the output signal of the circuit with Inductive Load.