Electrical Engineering: Circuit Design Questions

The question make no sense at all. HV / LV? 13kV, 450V, 110Vor 5V?

Mixing up star center neutral return with protective ground?

QUIT before you injure yourself or someone else.

I may be able to answer your first question, the second I have no idea what you are talking about.

Question 1:Most 3 phase motors are designed to be dual voltage;

Lets say 400 or 230 volts.

For a supply of 400 volt in this case we would wire the motor in star configuration, this is so that the windings are in series via connection at the star point

For a supply of 230 volt the windings are in parallel, no star point.

In this example the motor is delta connected at 230 volts, that means the windings are in directly wired across the phases. If you did the same at 400 volts you would have a motor burnout.

Best Regards

1. HV motor is star connected so that voltage stress on the windings is reduced to root three times of line voltage; reducing the insulation cost and chances of failure due to less application of voltage.

2.In Secondary circuit of voltage transformer(110 volt) middle phase (L2/Y-Phase ) is earthed to facilitate to complete ground fault current path in case of occurence of ground fault in secondary circuit of voltage transformer and blowing off of protective HRC fuse (preferably 2Amp rating ) to save the secondary voltage circuit.

Manindra