Single Phase Full Wave Controlled Rectifier with 'RL' load:
Operation of this mode can be divided between four modes
1) In positive half cycle of applied ac signal, SCR's T1 & T2 are forward bias & can be turned on at an angle α.
2) Load voltage is equal to positive instantaneous ac supply voltage. The load current is positive, ripple free, constant and equal to Io.
3) Due to positive polarity of load voltage & load current, load inductance will store energy.
1) At wt=ϖ, input supply is equal to zero & after ϖ it becomes negative. But inductance opposes any change through it.
2) In order to maintain a constant load current & also in same direction. A self inducedemf appears across 'L' as shown.
3) Due to this induced voltage, SCR's T1 & T2 are forward bais in spite the negative supply voltage.
4) The load voltage is negative & equal to instantaneous ac supply voltage whereas load current is positive.
5) Thus, load acts as source & stored energy in inductance is returned back to the ac supply.
1) At wt=ϖ+α SCR's T3 & T4 are turned on & T1, T2 are reversed bias.
2) Thus , process of conduction is transferred from T1,T2 to T3,T4.
3) Load voltage again becomes positive & energy is stored in inductor
4) T3, T4 conduct in negative half cycle from (ϖ+α) to 2ϖ
5) With positive load voltage & load current energy gets stored
1) At wt=2ϖ, input voltage passes through zero.
2) Inductive load will try to oppose any change in current if in order to maintain load current constant & in the same direction.
3) Induced emf is positive & maintains conducting SCR's T3 & T4 with reverse polarity also.
4) Thus VL is negative & equal to instantaneous ac supply voltage. Whereas load current continues to be positive.
5) Thus load acts as source & stored energy in inductance is returned back to ac supply
6) At wt=α or 2ϖ+α, T3 & T4 are commutated and T1,T2 are turned on.