Microprocessor control of a `hidden-link¿ convertor drive

This synchronous motor drive, unlike the DC link convertor drive, has a single mode of operation from starting to above synchronous speeds. The simple control scheme requires synchronism to the supply waveforms and rotor position. Hardware, software and interface circuits for a Z80 microprocessor-based controller are described. A modest clock rate of 2.5 MHz is sufficient and still leaves the microprocessor 88% idle. High levels of control, and possibly some diagnostic features, can therefore be included.