Often, when performing power circuit analysis using precision bridge resistance measurements of our large electric motors, we see values of resistance that are very small. Some of these are down in the milliohm or even micro ohm range. These actual resistance values can vary greatly with changes in temperature. However, the balance calculation between the three values on a three phase induction motor should not. A change in the resistance imbalance from .08% to .8% doesn't seem like a lot when in fact it is a 900% increase. This stresses the importance of getting good baseline data early for good trending and comparison.
For another example of power circuit analysis where a little thing made big things happen go to www.pdma.com and click on "The Case of the Broken Bolt".
