Good day.

I have a 200kw motor running through a soft starter at the moment. Previously it ran with a VSD, that burnt due to this matter.

We have redone a water treatment plant in 2012, and noticed that the voltage was good testing it with a multi meter. As soon as you start a motor it runs at almost 45% amps difference. If you run it through the standby generator, then the amps are fine.

Its also time dependant, and weather. Between peak hours its worse and if its winter even more.

Supply voltages: 405V, 411V and 412V.
Amps on the 200kw motor: 340A, 210A and 315A.

Generator voltages: 400V, 400V and 400V
Amps on the 200kw motor: 330A, 325A and 332A

This has been a big problem, as engineers of the electical supply company and engineers of Johannesburg and PE are batheled with this issue.

The supply company says they only supply voltage and not amps, duh I know that, but why did our voltage regulator poped as wel as 3 VSDs in 2 weeks time and then the motors started burning.

Any person than can give advise on this matter please.

I assume its poor load ballancing of towns on the gridline as we have our own 22kV line supplying the water treatment plant.

Ivan