Test: Advance Three Phase Converters - Electrical Engineering (EE) MCQ

Each SCR conducts for 60° or 2π/6 radians. 6 x 60 = 360°.

Each SCR conducts for 30° or π/6 radians. 12 x 30 = 360°.

Put n = 1 (fundamental component) and the rest of the given values in the above given equation.

 DF = cosα = cos45 = 0.707
Note that ripple free current does not mean that DF = 0. It means the current is continues in magnitude and direction, current will always contain harmonics (distortions) whether it is rippled or ripple free.

PF (power factor) = (distortion factor) x (current distortion factor).

Due to source inductance, SCRs cannot start and stop conducting immediately, hence a time occurs when both incoming and outgoing SCRs are conducting together. This delay is called as commutation angle or overlap period (μ).

2nd harmonics are absent in a 3-phase full converter, it has only odd number of harmonics i.e. 3rd, 5th etc.

 In a p-pulse controlled converter, each device conducts for p radians. p-pulse converter would have p devices. Hence, 2π/p x p = 2π = 360°.

Semi-converters can operate in 6-pulse modes gating the SCRs at appropriate intervals.

M-6 requires a transformer having a delta connected primary and a double star connected secondary such that 6 SCRs are connected to it on the secondary side.