Revolving and Evolving-Early dc Machines [Historical]

In an age largely characterized by information and communication technology, which uses more and more feeble currents, electrical power is experiencing a period of excellent health and heading toward a bright future. This success is largely due to electric motors, which are available in different types and powered by dc as well as ac sources operating at either utility or variable frequencies. The versatility and ubiquity of electric motors are so wide that they can be found almost everywhere: in many household appliances, technician power tools, building fans, factory machine tools, blowers and pumps of industrial fluid systems, cableways, railway and streetcar locomotives, computer disk drives, drivers and printers, and cell phone vibration alerts.