Answer:

To understand why option B is the correct answer, let's first understand what an M-6 controlled converter or a 6-pulse half-wave controlled converter is.

M-6 Controlled Converter:
An M-6 controlled converter is a type of rectifier circuit that converts alternating current (AC) into direct current (DC) using six thyristors. It is called an M-6 converter because it uses six thyristors arranged in a specific configuration.

Thyristors:
A thyristor is a semiconductor device that acts as a switch and allows current to flow in only one direction. Thyristors are commonly used in power electronic circuits for controlling AC power.

Working Principle of M-6 Controlled Converter:
The M-6 controlled converter works on the principle of phase control. It consists of a transformer and six thyristors connected in a specific configuration. The AC input voltage is applied to the primary winding of the transformer, and the secondary winding is connected to the thyristors.

The six thyristors are connected in a three-phase bridge configuration, with each phase having two thyristors connected in series. The thyristors are fired in a sequence to control the output DC voltage.

Why Option B is Correct:
Option B states that the transformer used in an M-6 controlled converter has a double star connected secondary winding. This means that the secondary winding of the transformer is connected in a star (or wye) configuration.

The star connection of the secondary winding is important because it provides a neutral point for the three-phase output. In an M-6 controlled converter, the output DC voltage is obtained by rectifying the three-phase AC voltage. The star connection allows for a balanced output and helps in reducing the harmonics in the output waveform.

The other options are not correct because:
- Option A: A double delta connected secondary winding does not provide a neutral point, which is necessary for a balanced output.
- Option C: A double delta connected primary winding is not relevant to the configuration of an M-6 controlled converter.
- Option D: Having six windings on both primary and secondary sides is not necessary for an M-6 controlled converter. The number of windings depends on the specific configuration and requirements of the converter.

Hence, option B is the correct answer as it describes the appropriate secondary winding configuration for an M-6 controlled converter.

Explanation:

The M-6 controlled converter or 6-pulse half-wave controlled converter is obtained by using a transformer with a double star connected secondary winding. Let's understand why option 'B' is the correct answer.

Controlled Converter:
A controlled converter is a power electronic device that converts AC power to DC power by controlling the conduction of the power semiconductor devices (such as thyristors). It consists of a transformer and a rectifier circuit.

6-Pulse Half-Wave Controlled Converter:
The 6-pulse half-wave controlled converter is a type of controlled converter that uses a 6-pulse rectification technique. It consists of a transformer with a double star connected secondary winding and a rectifier circuit with six power semiconductor devices.

Transformer:
A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. It consists of two or more coils of wire (windings) linked by a magnetic field.

Double Star Connected Secondary Winding:
In a double star connected secondary winding configuration, the secondary winding of the transformer is connected in a star (Y) arrangement. This means that the ends of the three windings are connected together and the three remaining ends are taken as the output terminals.

Advantages of Double Star Connected Secondary Winding:
1. It provides a balanced output voltage.
2. It allows the use of three-phase loads.
3. It reduces the harmonic distortion in the output voltage.

6-Windings on Both Primary and Secondary Sides:
The option 'D' suggests that the transformer has six windings on both the primary and secondary sides. However, a 6-pulse half-wave controlled converter does not require six windings on both sides. It only requires a double star connected secondary winding.

Conclusion:
In conclusion, the correct answer is option 'B' which states that the M-6 controlled converter or 6-pulse half-wave controlled converter is obtained by using a transformer with a double star connected secondary winding. This configuration provides a balanced output voltage and reduces harmonic distortion in the output voltage.