Introduction of three phase half wave uncontrolled rectifier
Figure A shows a three-phase half wave uncontrolled rectifier circuit using delta – star transformer. The anode of the diode D1, D2 and D3 are connected to the secondary winding of the transformer with R phase, Y phase and B phase respectively. The cathode of the three diodes is connected to the neutral point of the secondary winding. The resistive load is connected between neutral point and common cathode point of the diodes.
Three phase half wave rectifier circuit diagram
Working of three phase half wave uncontrolled rectifier
The three phase supply
voltage waveforms are shown in the figure B. The diode can block negative
voltage and it conducts when phase voltage is maximum of the three phases. The
effect of the transformer winding reactance is neglected. The working of three
phase uncontrolled rectifier is given below.
Point a:
The voltage of phase R becomes zero.
The voltage of phase B becomes positive with respect to phase Y resulting diode
D3 conducts. The load current flows through phase B – diode D3 – load
resistance RL – n.
Point b:
The voltage of phase Y becomes negative.
The voltage of phase R becomes positive with respect to phase B resulting diode
D1 conducts. The load current flows through phase R – diode D1 – load
resistance RL – n.
Point c:
The voltage of phase B becomes negative.
The voltage of phase Y becomes positive with respect to phase R resulting diode
D2 conducts. The load current flows through phase Y – diode D2 – load
resistance RL – n.
Waveform of three phase half wave rectifier
There are three diodes and
each diode conducts in a proper sequence of D3 – D2 – D1 – D3 and so on. The
conduction angle for each diode is 120 degree.
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