Characteristics of Load commutated CSI and Output
Points to be noted regarding load commutated CSI:
- It may be observed from the equation given earlier that, as the inverter frequency (f = 1/T) is increased, the turn-off time provided by the circuit decreases. But, the circuit commutation time, toff , should be more than the turn-off time of the thyristor, tq , for reliable operation. This means that there is an upper limit to the inverter frequency, beyond which the thyristors in the inverter circuit will fail to commutate.
- When the inverter frequency (f = 1/T) is low, or time period, T is high, the graph of i0(t)or v0(t) becomes flatter. As this graph is nearer to a square wave, it can be inferred that, for low inverter frequencies, the inverter has square wave output for load current or load voltage (i0/v0).
Output of load commutated CSI:
- When the inverter frequency (f=1/T) is high, or time period, T is low, the waveform of V0 or i0. As this graph is closer to a sine wave, it can be noted that, for higher frequency, the CSI has sinusoidal wave shape for load (output) current or voltage.