2 Introduction to electric motor drives

An electric motor-drive system, as shown in Figure 2-1, takes power from the AC mains, rectifies it to a DC voltage, and inverts the DC back to AC with variable magnitude and frequency based on load demand through complex feedback control algorithms.

A motor-drive system typically has two voltage domains: the “high-voltage” domain and the “low-voltage” domain. The microcontroller or digital signal processor, typically on the low-voltage domain, receives feedback signals (voltage, current, temperature, etc.) from the three-phase IGBT power stage and generates pulse-width modulated signals for controlling the power switching transistors and other high-side power circuitry. Such systems demand resilient and reliable galvanic isolation to isolate high-voltage circuits from low-voltage circuits. An isolation architecture enables reliable operation of motor-drive systems, preventing damage to expensive circuitry by breaking the ground loops between the high- and low- voltage circuits and helping protect human operators from high voltages.