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Thread: Circuit Diagram for a Capacitor-Start Capacitor-Run Single Phase Incution Motor

  1. #1
    Associate Engineer
    Join Date
    Jan 2016

    Circuit Diagram for a Capacitor-Start Capacitor-Run Single Phase Incution Motor

    I have created a circuit diagram for a single phase CSCR induction motor, but only for the purpose of calculating start-up current (i.e. motor speed is at, or very near, zero RPM). I have created this diagram because: 1) I do not have the tools & knowledge required to generate the Steinmetz equivalent circuit with the capacitors included; and 2) The values for each of these circuit elements can be measured using an LCR meter (except for my beta term).

    Please review the attached circuit diagram and let me know if you find anything incorrect. Or, if it looks like this is a reasonable approximation for near zero speed currents then please give me a confirmation.

    The beta term I have in the diagram is something I conjured to represent the magnetic flux that the roto bars consume. My idea is that the measured inductance of each stator coil will be greater than the actual stator coil inductance during the start-up event because the LCR meter does not pass a sufficiently large current that a significant portion of the resulting magnetic field would pass through the rotor bar loops. For one motor tested on one power supply, I have found that my calculated start-up current is within 3% of the measured start-up current when I set beta = 50%. Does it make sense that, during the start-up event, the rotor would consume half of the magnetic flux generated by the stator coils?

    Thank you in advance for your help!
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