Overview
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Single-phase AC is the most commonly used power supply, and an induction
motor is robust and its cost is low. So the induction motor that is powered
with single-phase AC can be readily usable motor.
Unlike three-phase AC, however, single-phase AC alone cannot generate the
rotating magnetic field and the direction of the rotation cannot be specified
either. So it cannot start the induction motor.
For this reason, an auxiliary winding needs to be placed to help the motor
start.
This note presents the use of magnetic field analysis to evaluate the starting
performance of the induction motor with use of the auxiliary winding. |
Flux Density Distribution / Eddy Current Density Distribution
Fig. 1 shows the flux density distribution right after the motor startup.
And Fig. 2 shows the eddy current density distribution of the secondary
conductor bars.
The flux generated by the winding causes eddy currents in the secondary
conductor bars, and a rotating magnetic field is generated. |
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Starting Performance
Fig. 3 shows the rotation speed versus time graph, and Fig. 4 shows the
torque versus time graph.
The time from the motor startup to when the motor reaches the no load steady
speed is determined by the capacitance of the capacitor. The slip is zero
when the rotation speed reaches the synchronous speed, and the average
torque is zero. |
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