Compare ON-OFF Control and Phase Control.

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Sr. No.	ON-OFF Control	Phase Control
1	Output Voltage is controlled by controlling the number of ON Cycles 'n' and number of OFF Cycles 'm'.	Output voltage is controlled by controlling the phase angle or firing angle of the thyristor.
2	Thyristor conducts $180^0$ as it is triggered at $\alpha = 0$	Thyristor is triggered at some angle depending upon output power.
3	No harmonic due to the switching at zero crossing instants.	Harmonic are present due to switching at instants other than zero crossing.
4	Load voltage waveform is not distorted	Load voltage waveform is distorted. Distortion increases with increase in $\alpha$
5	Average load voltage and load current is zero	Average load voltage and load current is zero
6	Load voltage will be equal to full supply voltage or zero.Hence output waveform has high voltage fluctuation.	Supply voltage is applied partially to load.Hence there is less voltage fluctuation.
7	Applications: Industrial heating, speed control of induction motor erc.	Applications: Heat control, light dimmer, fan regulator.

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