induction motor and capacitance
HI all. I am new to CE.
consider this situation:
we have an induction motor in hand , which is of capacitor-start-capacitor-run type. the datasheet of the motor says that its maximum speed is 380 rpm.
the motor has a 2 microfarad capacitor fitted external to its body.
it now becomes evident that the 2 mf capacitor enables the motor to run at 380 rpm.
now how do we determine the speed of the motor if its capacitor was replaced with that of a different capacitance value.
we do not have any tachometers in hand to measure the spindle speed physically. so how do we determine the speed mathematically ?
my approach is as follows : for example if the 2 mf cap was replaced with a 1 mf cap, then the speed will vary proportionally, that is it will be reduced by half to 190 rpm.
is this calculation correct ? does the speed vary with capacitance linearly ?
consider this situation:
we have an induction motor in hand , which is of capacitor-start-capacitor-run type. the datasheet of the motor says that its maximum speed is 380 rpm.
the motor has a 2 microfarad capacitor fitted external to its body.
it now becomes evident that the 2 mf capacitor enables the motor to run at 380 rpm.
now how do we determine the speed of the motor if its capacitor was replaced with that of a different capacitance value.
we do not have any tachometers in hand to measure the spindle speed physically. so how do we determine the speed mathematically ?
my approach is as follows : for example if the 2 mf cap was replaced with a 1 mf cap, then the speed will vary proportionally, that is it will be reduced by half to 190 rpm.
is this calculation correct ? does the speed vary with capacitance linearly ?
Replies
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Ramani Aswath
That is not the purpose of the capacitor. The run capacitor ensures a proper rotating magnetic field is maintained. It has to be sized for each capacity of motor and the winding. Changing the value will drastically affect performance.Pawl supiranis this calculation correct ? does the speed vary with capacitance linearly ?
The speed cannot be controlled by varying the running capacitance.
Motor Capacitor
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