Determination of Induction-Motor Parameters


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Determination of Induction-Motor Parameters

  • DC Test

    • Determines R1
    • Connect any two stator leads to a variable-voltage DC power supply
    • Adjust the power supply to provide rated stator current
    • Determine the resistance from the voltmeter and ammeter readings



For a Y-Connected Stator



For a Delta-Connected Stator



Determination of Induction-Motor Parameters





Simplified Equivalent Circuit









How Is the Blocked-Rotor Impedance Divided?



Determination of Induction-Motor Parameters

  • No-Load Test

    • Determine the magnetizing reactance, XM and combined core, friction, and windage losses.
    • Connect as for blocked-rotor test (next slide).
    • The rotor is unblocked and allowed to run unloaded at rated voltage and rated frequency.




Determination of Induction-Motor Parameters

  • At no-load, the speed is very close to synchronous speed – the slip is =0, causing the current in R2/s to be very small, and will be ignored i the calculations.

  • IM>>Ife, so I0 = IM.







Example 5.16

  • The following data were obtained from no-load, blocked-rotor, and DC tests of a three-phase, wye-connected, 40-hp, 60-Hz, 460-V, design B induction motor whose rated current is 57.8A. The blocked-rotor test was made at 15 Hz.
















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