Power Electronics Lab Experiments

Study of Single Phase Full Wave AC Voltage Controller with R and RL load

Nov 27 2023

Objective

Study of Single Phase Full Wave AC Voltage Controller with R( Lamp Load) and RL (motor load).

Apparatus Required:

High Voltage Power Electronics Lab
4mm Patch Cords
Product Tutorials

Circuit Diagram

Single Phase Full Wave AC Voltage Controller with Lamp Load

Single Phase Full Wave AC Voltage Controller with Motor Load

Procedure:

Make sure that there is no connection on the Work Bench initially.

Switch on the three phase MCB of back panel.
Red, Yellow and Blue indicator glow at front panel.
Connect +12V, +5V and ground (GND) and connect 18-0-18 at ramp comparator firing circuit from single phase low voltage power supply.
Use SCR1 and SCR2 from SCR Assembly and to construct single phase full wave AC voltage controller.
Connect cathode of SCR1 to anode of SCR2 and connect cathode of SCR2 to anode of SCR1.
Connect Line Terminal (L) from single phase supply to anode of SCR1 or cathode of SCR2.
Connect the one terminal of load from Load Assembly to common cathode anode terminal of SCR1 and SCR2 and other terminal of load is connect to neutral terminal (N) of single phase supply.
Connect gate pulse G1 at gate (G) of SCR1 and connect K1 at cathode of SCR1 from ramp comparator firing circuit.
Connect gate pulse G3 at gate (G) of SCR2 and connect K3 at cathode of SCR2 from ramp comparator firing circuit.
Verify the connections before switch on the MCB of single phase supply.
Connect BNC to BNC cable at CH1 of oscilloscope to output of Power Scope A.
Switch of ATT of A is x 100 position and switch of coupling of A is AC position.
Connect input of Power Scope A to the load.
Connect the Universal Motor at the Load.
Switch on MCB of Single Phase Supply and observe the output waveform of load terminals on the oscilloscope.
Connect the AC Voltmeter at the load and measure the output AC voltage across the load.

Observe the output waveform at the load as shown in figure

Observation table:

R load:

Firing angle(α)	V_avg(Theoretical)	V_avg(Practical)	Time Period(ms)	V_rms(Theoretical)	V_rms(Practical)
59.4	0	-3.58	3.3	206.3	229
108	0	-6.9	6	127.33	161
120	0	-1.74	6.7	101.69	151

RL load without freewheeling diode:

Firing angle(α)	V_avg(Theoretical)	V_avg(Practical)	Time Period(ms)	V_rms(Theoretical)	V_rms(Practical)	β(ms)	β(degrees)
60	0	-7.51	3.33	214.98	227	11.5	207
90	0	-8.19	5	168.36	183	11.3	212.4
108	0	-3.55	6	134.59	152	12.3	221.4
120	0	-4.82	118.979	118.979	118	11.8	212.4

Equations:

R Load

V_rms = V_s[1/π[(π-α) + sin2α/2]] ^1/2

RL Load

Experimental Waveforms:

R load:

RL load:

Conclusion: By varying the firing angle control potentiometer of ramp comparator firing circuit, output voltage across the loads, their waveform for single phase full wave AC voltage controller with R and RL Loads was observed.