Small Scale VFD Noise Suppression

I'd suggest telling your pump supplier that there are no shortage of competing suppliers for pumps, and that if they aren't prepared to help, you will be forced to go elsewhere.

I would question the need for a phase loss monitor for a motor operated from a VFD. All of the VFDs I am aware of would trip off line if one of the phase currents was significantly lower than the others, a better form of phase loss monitring than the (likely) voltage based version you have built-in (I say that because of its ability to be fooled by a PWM output).

I would question it as well.

I am talking about operating these pumps on a power supply shared by a VFD for another motor, not using the VFD to drive the pump.

The pumps have a contactor built in, which the phase monitor commands. This contactor alone would not permit operation on a VFD. The purpose of this internal control is to only allow the pump to operate with the correct rotation, all three phases present and the thermal cut-out circuit closed. These are considered portable pumps and these features make them "plug and play".

I am looking for a way to filter the incoming power supply within the chamber containing the phase monitor and contactor.

JRaef,

My reference to a Load Reactor in my OP is incorrect, It should be Line Reactor.

Sorry for the confusion.

H JRaef. He said that motors controlled by VFDs were sharing the same line, not that the pump was driven by a VFD.

Edit: Sorry - he had already pointed that out - just ignore me!

If you have explained this problem to the phase module supplier in the same clear way as you have here, and they have balked at providing either a solution or information, you might need to seek a different phase module supplier.

From an overall system view, one should examine the cost of a perhaps large line reactor on a VFD vs. a perhaps smaller filter on the phase module.

I have explained it to the supplier. Everything is market driven, every improvement, every innovation, must be justified for consideration by management in Sweden (as it would be for anywhere).

It is a requirement in Europe, to have line and load filters on VFDs, which makes for an easy excuse.

Most phase monitors, whether voltage referenced or zero crossing networked, will not tolerate noise.

There is a limited amount of space inside the head of the pump.

I don't know enough about filter design to develop a filter that would work at such low current levels (input of the phase monitor).

I have offered to supply the pumps without the system, but the customers want it.

What I need is what you mentioned, a smaller filter at the phase module.

If the phase detection module has low input current requirements then you may get away with a resister/capacitor 3 phase filter JUST feeding the detection module. Is it easy to disconnect the detection module from the 3 phase supply to insert a filter?

How big is the pump? What line voltage? Frequency? Make? Part number?

It might be easier to test a similar pump from another manufacturer. If this pump phase module is so sensitive that some harmonics are disturbing it, it is not well designed. Harmonics filters are expensive and are often custom designed (should be). Be wary of somebody selling you a simple capacitor bank. It might help short term but cause various problems later. There are many discussion on this site on this subject.

If it is affected by the VFD high frequency switching noise, revise the grounding scheme of the VFD, its motor, your pump, and the power feeder. Something might be floating or grounded at the wrong place.

Good luck.

The pumps with this protection system range from 2 hp to 30 hp 3 phase 60 Hz 230-575v.

There has to be a way to "decouple" the line voltage input so that the phase monitor "sees" only the 60Hz sine wave.

If the power supply influnced by the VFD was also supplying power to electronic equipment (computors, controllers, ect.) the need for a line filter or reactor on the VFD would most certainly be necessary. But, if you have for example, a dredge where the main dredge motor is driven by a VFD, supplied by a generator, then the requirement for a line reactor on the VFD just to supply clean power to a 10hp pump becomes a hard argument.

Everybody, thanks for the help.