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Help for an Exam


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#1 rical

rical

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Posted 27 October 2005 - 06:08 PM

A 1 phase induction motor is drawing 10 Amps when connected to the supply. It is required a device that increases the "efficiency" of the motor. During some tests a device was connected in parallel to the motor and the current decreased to 8 amps. When a second device was connected in parallel to the motor the current decreased down to 6 Amps. Question: what device will cause the decrease of the current?

#2 marke

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Posted 27 October 2005 - 06:38 PM

Hello rical

Welcome to the forum.

1) If you connect somehing in parallel with the motor and we assume that the supply impedance is low, you will not affect the efficiency of the motor. The same voltage will appear across the motor terminals and the same current will flow into the motor.
2) The current flowing from the supply is a combination of inductive magnetising current and resistive work current. Connecting a capacitor across the motor will reduce the inductive cruuent drawn from the supply but will not alter the current into the motor.
Have a look at our power factor correction page for more information.
http://www.lmphotonics.com/pwrfact.htm

Best regards,




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