# Why is the voltage more in case of same polarity during a polarity test of induction motor?

I was performing experiment in the lab of my university. The experiment was supposed to be performed on a squirrel cage induction motor. But I performed it on a three phase slip ring I.M with its rotor short circuited. All the voltages used were AC voltages. I applied 100 V across one terminal of phase(A1) and neutral(N) of a star connected stator winding. When the polarity was same (i.e. the star point was at A2,B2,C2), the voltage across A1 and B1 came out to be 84 V, which is less than 100 V. My question is: Shouldn't it be more than 100 V because the voltages induced in both the windings are additive in nature or am I interpreting anything wrong? When we change the star point to A2,B1,C2, then the voltage across A1 and B2 comes out to be more than 100 V. In this case, shouldn't it be less than 100 V?

• You would do well to specify whether the voltages are AC or not. In addition a diagram or two would be useful to helping understand your question. Have the diagram include the excitation points and the measurement points. Jan 19, 2016 at 14:22
• @MichaelKaras I've done that, but still I have not got any responses. I don't know why? Jan 20, 2016 at 14:16