In a McMurray inverter, diodes are connected in inverse parallel to thyristors to 1. Protect the thyristor 2. Make the turn off of the thyristor successful 3. Make the turn on of the thyristor successful 4. Provide path to the reactive component of the load current Which of the above statements are correct?

In a McMurray inverter, diodes are connected in inverse parallel to thyristors to 1. Protect the thyristor 2. Make the turn off of the thyristor successful 3. Make the turn on of the thyristor successful 4. Provide path to the reactive component of the load current Which of the above statements are correct? Correct Answer 2 and 4

The circuit diagrams of single-phase half-bridge and full-bridge inverter are as shown below.

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• In a half-bridge inverter, thyristors T1 and T2 are in series across the source; in a full-bridge inverter, thyristors T1, T4 or T3, T2 are also in series across the source.
• During inverter operation, it should be ensured that two SCRs in the same branch, such as T1, T2 in the half-bridge inverter, do not conduct simultaneously as this would lead a direct short circuit of the source.
• For a resistive load, two SCRs in half-bridge inverter and four SCRs in full bridge inverter would adequate, because load current i0 and v0 would always be in phase with each other.
• But this is not the case with the other type of loads.
• For such type of loads, current i0 will not be in phase with voltage v0 and didoes connected in antiparallel with thyristors will allow the current to flow when the main thyristors are turned off.
• These diodes are known as feedback didoes, the main function is to freewheel the load current.