Three phase converters

1) Three period converters provide greater manufacturing voltage that is typical.

2) Frequency of ripples on production voltage is greater compared with that of solitary duration converter.

3) Hence the filtering demands for smoothing out load present & load voltage are easier.

4) Of these reasons, three duration converters are extensively present in high power price that is variable.

Three phase semiconverters

1) Three phase that is revolution that is solitary is connected to form a three period half revolution converter.

2) Similarly three phase semiconverter makes usage of 3 SCRs T1, T3 & T5 and 3 diodes D2, D4& D6

3) R,Y,B are phase voltages with regards to 'N'.

4) To the circuit shown above whenever any device conducts, line voltage is used across load. so line voltage are essential to draw

5) Phase change between two line voltages is 60 level & between two stage voltages it's 120 level

6) Each phase & line voltage is wave that is sine the frequency of 50 Hz.

Operation of semiconverters with R load

1) With purely resistive load current will be in phase with load voltage.

2) Depending on value of firing angle, circuit can operate in two different modes.

T1 is triggered at α=30. SCR T1 and D6 conduct and line voltage RY is applied to the load from is more positive so conducts. Therefore, line voltage RB is applied to load. This continues up to firing

the output voltage is continuous so called continuous mode of operation.

for some duration of time no device conducts so called discontinuous mode of operation.