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Pennwood Wrong Wattage for Pennwood numechron motor

78Rus

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Dec 5, 2011
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Saint-Petersburg
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Hi! I have two motors (pennwood numechron) for desktop clock. Wattage indicated as 3,7 W. But when connect ammeter is obtained 50mA, which corresponds to 55W. Why so? Thanks!
 

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praezis

Registered User
Feb 11, 2008
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Germany
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Hi! I have two motors (pennwood numechron) for desktop clock. Wattage indicated as 3,7 W. But when connect ammeter is obtained 50mA, which corresponds to 55W. Why so? Thanks!
...because 120V x 50mA gives 6W, no 55W :confused:
...because with inductive loads there is a phase shift between AC voltage and current, and then V x A is different from Watt.
...because a running motor generates his EMF voltage which is subtracted from his supply voltage.

Regards,
Frank