Three phase breaker problem

[FilipeG]

Hi

My problem is i have one three phase source feeding my motor(7.5kW) and then i have the same source feeding a vsd and another motor and i want to separate electrally electrically using a three phase breaker. When i check the voltage going to vsd, it should be zero but there is one sine wave with amplitude 1.5 V.

I tried to fragment my simulink code and when i use only a source a three phase breaker and a motor, it works fine.
Anyone could tell me an opinion and an advice!?

Best regards

 

[jraef]

Are you are saying that you have the 3 phases feeding a VFD being held OPEN by a 3 pole circuit breaker, but you are still reading a voltage of 1.5VAC on the LOAD SIDE of that circuit breaker or line side of the VFD?

If so, 1.5VAC measured from where to where? Phase to phase, or phase to ground? All phases? How long has the circuit breaker been open at the time that you take the measurement? You do realize I hope that a VFD has DC bus capacitors that will store a significant charge for sometimes several minutes after de-energization. A 1.5V ripple could simply be the leakage through the diodes if the measurement was taken too soon.

"Will work for (the memory of) salami"

 

[FilipeG]

yes, im reading a voltage of 1.5V AC on the load side of the circuit breaker.
i forget to say that is 1.5V AC phase to phase, the circuit breaker is always open during simulation time 1 second, so ideally in output would have 0 V, but seems that 1.5V come from VFD.

 

[waross]

It's probably induction from a nearby circuit. I have seen small voltages induced by nearby cables and by ballast type light fixtures.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

This voltage is measured in a simulation?

 

[John2025]

High impedance digital meter? You will probably see all kinds of stray voltages in a factory.

 

[FilipeG]

yes,it was measured in a simulation.