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Temperature-Sensitive Speed Control Circuit for DC Fan Motors

IP.com Disclosure Number: IPCOM000046976D
Original Publication Date: 1983-Sep-01
Included in the Prior Art Database: 2005-Feb-07

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Shakib, J [+details]


A speed control circuit for direct current (DC) fan motors is described which is particularly useful for the case where the fan is located inside of an electronic equipment cabinet and is used for purposes of cooling the electronic equipment therein. In such case, the circuit varies the speed of the fan to keep a constant temperature inside the equipment enclosure. Consequently, at lower ambient temperatures, the fan will run at lower than the normal rated speed, hence reducing the acoustical noise generated by the fan. Temperature sensors in the form of thermistors 1, 2 and 3 are used as the controlling elements. These thermistors 1, 2 and 3 are located at various points inside the electronic equipment enclosure.