frequency. If the dc source is not controllable, a dc-dc converter may be inserted
between the dc source and the inverter.
The PWM inverter is useful in a constant volts/hertz application because the
amplitude of the output voltage can be adjusted by changing the amplitude modulation
ratio ma. The dc input to the inverter can come from an uncontrolled
source in this case. The configuration in Fig. 8-34 is classified as an ac-ac converter
with a dc link between the two ac voltages.