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Computing the Lumped Parameters of Induction Machine Models

Motors and generators with MotorSolve

The equivalent circuit analysis is based on computing the lumped parameters of induction machine models. The procedure for computing the lumped parameters is outlined in the IEEE Standards test procedure for Polyphase Induction Motors and generator (2004). Following this procedure, MotorSolve IM performs no-load saturation, locked-rotor and impedance test simulations to evaluate the circuit parameters. The tests are based on FEA solves and include accurate estimation of core losses. In this analysis mode, computation of the lumped parameters allows the user to specify the leakage ratios between the rotor and stator.

In addition, MotorSolve IM offers another option for calculating the equivalent circuit parameters that approximate the leakage inductances using an FEA based approach that accurately separates rotor and stator leakage fields with the correct ratio. Some examples using the equivalent circuit based analysis of a 17 bar - 24 slot machine are given below.

Computing the lumped parameters of induction machine models



The equivalent circuit based analysis can provide all essential results to the designer at any stage of the design process. It gives the user the ability to study designs under different operating conditions or as functions of synchronous speed, slip, etc. Model characteristics useful to both machine and inverter designers can be generated instantly (see example on the left). The accuracy level of the results can be controlled using a single parameter that the user sets. Typical results which can be computed using the equivalent circuit analysis include torque, efficiency, voltage, current, power factor, etc. Some examples are shown next. Note that the results shown were obtained using the equivalent circuit analysis method at different synchronous speeds. As such, each curve label corresponds to synchronous speed simulation at that value.

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Model summary in the form of a nameplate computed using equivalent circuit analysis is shown here.

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Induction motor speed-torque and other typical graphs.

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Various loss components vs rotor speed

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