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To observe the working operation of 1-φ to 1-φ Cycloconverter with R and RL loads and to plot the voltage waveforms across the load.

Apparatus Required

☞Trainer kit- Cycloconverter -1 No

☞Patch Chords - Sufficient Nos

☞Load - Internal Resistive Load

☞CRO - 1 No

☞10:1 CRO Probe - 1 No

Circuit diagram

Circuit Diagram

Figure: Single Phase to Single Phase Cycloconverter



CRO Settings

☞Time (X) Axis : 5ms/div

☞Voltage (Y) Axis : 20V/div

☞Probe : 1:10 CRO Probe is suitable one.


Initial Settings

☞Ensure the 230V Power Supply is in proper with Tester.

☞Ensure the CRO is working properly with probe checking and proper ground line axis.


Mimic Diagram

single to single cyclo converter

Experiment Steps

☞Switch on the main supply to the firing circuit.

☞Observe the test points and trigger outputs by changing frequency division and by varying firing angle, using CRO.

☞Switch OFF the supply to the firing circuit.

☞Make the power circuit connections as per the circuit diagram.

☞Connect the firing pulses from the firing circuit to the respective SCRs in the power circuit.

☞Switch ON the supply to firing circuit and the main supply.

☞Set the frequency division.

☞Vary the firing angle potentiometer and observe the waveforms across the load and note down the readings.

☞Repeat the experiment for different firing angles.

☞Switch OFF the supply to the firing circuit and main supply.


Note: If the connections are wrong the kit will get damage.




Total Time (ms)

F select Position in (Hz)

Firing angle

(α in Degree)





F= 50












Data from input waveform:

Total Time for one cycle = 20ms For one cycle = 360 ° Calculate for 1ms = 360/20 For 1ms = 18 degree

Calculate α:

Calculate off time of scr from output waveform = eg.4ms Then αvalue is = 4*18= 72degree

Calculate Output Frequency:

Total Time for one cycle (T) = 20ms So, F= (1/T) T in Sec = 1/ (20*10-3) = 50Hz

Model graph

Model graph

Figure : input voltage and load voltage


Output Waveform

Frequency Select =F

Frequency Select =f/2

Frequency Select =f/2

Frequency Select