The current-source input (CSI) inverter produces a voltage
waveform that looks more like an ac sine wave and current waveform that
looks similar to the original on/off square wave of the earliest inverters
that cycled SCRs on and off in sequence. This type of inverter uses transistors
to control the output voltage and current. The on-time and off-time of
the transistor are adjusted to create a change in frequency for the inverter.
The amplitude of each wave can also be adjusted to change the amount of
voltage at the output. This means that the CSI inverter like the previous
inverters can adjust voltage and frequency usable in variable-frequency
motor drive applications or other applications that require variable voltage
and frequency. Fig. 1 shows the voltage and current waveform for the CSI
inverter.

Above: Fig. 1: Voltage and current waveform for the current-source input
(CSI) inverter.
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