Electric generators and motors: An overview

Abstract

Starting with Faraday's law of electromagnetic induction in 1831, electric (electromagnetic) machines have been developed ever since as “assembles” of electric and magnetic coupled circuits that convert mechanical to electrical energy (in generators) and vice versa (in motors), via magnetic energy storage. Generators and motors are reversible. The Maxwell four equations (laws) later in 19th Century have prompted the rapid development of all basic (DC. brush and travelling field AC machines by 1900. Then by 1930 AC (alternating current) power (energy) systems evolved by connecting in parallel electric synchronous generators (with voltage boost and buck electric transformers for efficient AC power transmission lines) of rather constant frequency and voltage, driven by turbines (prime movers) that harness fossil (coal, gas or nuclear fuels), thermal or hydro energy. The last 50 years have witnessed a dramatic extension of generators power/unit, renewable energy generators and of variable speed AC motor drives in applications with variable output such as ventilators, pumps compressors, conveyors, orr-mills, electric transport (mobility), industrial automation, robotics, home appliances and info — gadgets. This formidable development, required by the need of more but cleaner energy, was mainly driven by power electronics, better materials, better modeling, design methodologies and digital control. This humble inaugural overview attempts to combine a brief history of electrical generators and motors with recent progress and trends in their design and control, for representative applications.