A four-pole, single-phase, 120 V, 60 Hz induction motor gave the following standstill impedances when tested at rated frequency: Main winding : Zm =1.5+j4 ohms Auxiliary winding : Za =3+j6 ohms a) Determine the value of external resistance to be inserted in series with the auxiliary winding to obtain maximum starting torque as a resistor split-phase motor. b) Determine the value of the capacitor to be inserted in series with the auxiliary winding to obtain maximum starting torque as a capacitor-start motor. c) Determine the value of the capacitor to be inserted in series with the auxiliary winding to obtain maximum starting torque per ampere of the starting current as a capacitor-start motor. d) Compare the starting torques and starting currents in parts (a), (b), and (c) expressed as per unit of the starting torque without any external element in the auxiliary circuit, when operated at 120V, 60Hz.
A four-pole, single-phase, 120 V, 60 Hz induction motor gave the following standstill impedances when tested at rated frequency:
Main winding : Zm =1.5+j4 ohms
Auxiliary winding : Za =3+j6 ohms
a) Determine the value of external resistance to be inserted in series with the auxiliary winding to obtain maximum starting torque as a resistor split-phase motor.
b) Determine the value of the capacitor to be inserted in series with the auxiliary winding to obtain maximum starting torque as a capacitor-start motor.
c) Determine the value of the capacitor to be inserted in series with the auxiliary winding to obtain maximum starting torque per ampere of the starting current as a capacitor-start motor.
d) Compare the starting torques and starting currents in parts (a), (b), and (c) expressed as per unit of the starting torque without any external element in the auxiliary circuit, when operated at 120V, 60Hz.
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