Article
Article
Universal motor
Article By:
Kosow, Irving L. Series Editor, Electrical Engineering Technology, John Wiley & Sons, Inc., Marietta, Georgia.
Last reviewed:August 2020
DOI:https://doi.org/10.1036/1097-8542.721900
A series motor built to operate on either alternating current (ac) or direct current (dc). It is normally designed for capacities less than 1 hp (0.75 kW) and usually operated at high speed, 3500 revolutions/min loaded and 8000 to 10,000 revolutions/min unloaded. For lower speeds, reduction gears are often employed, as in the case of electric hand drills or food mixers. As in all series motors, the rotor speed increases as the load decreases, and the no-load speed is limited only by friction and windage losses. To obtain more constant speed with variations in load, a centrifugal governor may be used to switch in or out a small resistor in series with the armature as in Fig. 1.
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