What Is Pulse-Width-Modulation (PWM)?
A PWM inverter, unlike the ferroresonant type, employs high speed switching power devices to generate a series of “pulses” in the inverter bridge to “simulate” a sine wave. This signal is then filtered and fed to the load through a linear transformer. Because the PWM employs a non-regulating linear transformer (rather than a non-linear regulator such as the ferroresonant type), a fairly complex network of feedback circuits is required to maintain the output voltage and current at the correct levels for the load. PWM inverters were first developed for Electronic Data Processing (EDP) applications, typically much cleaner and environmentally controlled installations than the industrial applications for which the much more rugged ferroresonant design is intended for. It has only been in the last few years that PWM inverters (and UPS systems) have become available for industrial applications. Many of the PWM units being marketed as Industrial Systems, however, are not ruggedized to withstan
