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single phase domestic fan speed control

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Posted 23 March 2004 - 03:56 AM

speed is =120*f/p .in single phase motors we dont control freq. then how speed is changed

#2 marke


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Posted 23 March 2004 - 07:28 PM


Many fan motors have special induction motors whereby the reistance of the rotor circuit is higher than normal This results in a very differnt torque speed curve and allows for torque control by varying the voltage applied to the motor. This is not direct speed control, but ast the torque increases with speed, if you reduce the torque produced by the motor, it will slow until the torque produced equals the torque consumed by the fan. This is often done by a triac controller similar to (but not the same as) a domestic light dimmer.
This technique must not be applied to standard cage induction motors!!

Best regards

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