In the induction motor equivalent circuit (either Thevenin or otherwise), the rotor, and stator leakages and reactances are necessary for any useful calculations.

How does one estimate leakages and reactances?

  1. Without computational electromagnetics and
  2. Without building the motor

What relations are there to do this?

In studying this genetic optimization paper for induction motors, and they reference one paper and one book for doing this, so there must be a way!

Thanks in advance!

  • \$\begingroup\$ That just leaves good old fashioned experience or measuring ones already built. \$\endgroup\$ – Andy aka Feb 2 '17 at 19:49

By having a motor those model parameter can be measured from a powered motor or by using it as a generator. As motor it must have a variable and known load. The current, rpm and torque are expressed as equations derived from the model. A series of tests are performed and the model parameters are fitted by choosing those parameter values that imply the closest results for the measured values.

If the motor is only a detailed 3d model including the materials and geometry, the measurements can be done virtually in full physics simulation software. That software is very expensive.

Addendum: Some good induction motor designs have stayed around a very long time. There exists handbooks that have practical design equations for some of those motor designs. The designs allow some amount of variation without causing the equations to lose their usability.

In terms of electromagnetism those design equations are approximations - ie. computational electromagnetics in a coarse form. They're based on graphical and empirical methods, but still can produce a proper estimate for the equivqlent circuit and the behaviour with a load.

A set of design equations is valid only for one design assuming it's circle of validity has not been exceeded by too large variation.

An example: http://publish.illinois.edu/grainger-ceme/files/2014/06/CEME1109HarleyGeorgiaTech.pdf

  • \$\begingroup\$ Gotcha. So the only two methods are: Building a motor and testing it, OR simulating a motor with computational electromagnetics (expensive). \$\endgroup\$ – Jonny Hyman Feb 3 '17 at 3:56
  • \$\begingroup\$ @Jonny Exactly not just that rigid. See the addendum. \$\endgroup\$ – user287001 Feb 3 '17 at 17:19

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