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The impedance of the main and auxiliary windings of a 1/3-hp, 120-V, 60-Hz. capacitor-start motor are given as Zm = (4.6 + j3.8) Ω and Za = (9.6 + j3.6) Ω Determine the value of the starting capacitance
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The impedance of the main and auxiliary windings of a 1/3-hp, 120-V, 60-Hz. capacitor-start motor are given as

Zm = (4.6 + j3.8) Ω and Za = (9.6 + j3.6) Ω

Determine the value of the starting capacitance that will cause the main and auxiliary winding currents to be in quadrature at starting.

User Hvester
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Final answer:

To find the starting capacitance for a capacitor-start motor, calculate the capacitive reactance that aligns the currents using the given impedances and then solve for the capacitance value using the formula relating capacitive reactance, frequency, and capacitance.

Step-by-step explanation:

The student is asking how to calculate the value of the starting capacitance that will cause the main and auxiliary winding currents of a capacitor-start motor to be in quadrature at the start. Impedance of the main (Zm) and auxiliary (Za) windings are provided, and the task is to find the right capacitor value that aligns the phase of the two windings' currents. The formula for calculating the capacitive reactance that will bring the currents in quadrature is Xc = |Za| - |Zm|, where Xc is the capacitive reactance, |Za| and |Zm| are the magnitudes of the auxiliary and main winding impedances respectively. To find the value of the starting capacitance, we can use the relationship Xc = 1/(2πfC), where f is the frequency and C is the capacitance. By rearranging the equation, we can solve for C to find the needed starting capacitance.

User Nikhil Gupta
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7.5k points
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