Half of all the electricity made in the world is turned into motion by electric motors. Every one of them works by two facts: a current in a magnetic field feels a force, and a changing field induces a voltage. Arrange copper and iron so the force always pushes the same way round and you have a motor; feed it the right current at the right moment from a handful of transistors and you have a drive. Run on the page: magnets, iron and the air gap; force, torque and the load; the brushed DC motor and its chopper; three-phase and the rotating field; induction, synchronous, permanent-magnet, brushless, stepper and reluctance machines; the inverter and its modulation; feedback, sensors and field-oriented control; losses, heat and design. Spin the field, load the shaft, switch the transistors and close the loop — every current and torque computed by the page.
Every field, current, torque and number on these pages is computed by the page or cited with its source; your progress stays in this browser. Nothing here asks you to wire, open or test anything connected to the mains, and nothing here is firmware or a design: real motors and drives are designed, wired and commissioned by qualified people with the right equipment. The course names no product or company outside its history. Not affiliated with or endorsed by any organisation, manufacturer, standards body, publisher or author mentioned here.