vfd noise on xducer

[bb3030]

I am on a diesel electric boat that has vfd's controlling main propulsion. The boat has 4 1700 kw generators - 480 volts, 60 hz. Multi-tek multifunction xducers are monitoring each generator and sending info to a power management system via modbus.

When drives go above 80%, generator xducers begin xmitting a signal that generators are running at 40 hz. The signal lasts for approx 3 seconds, then goes back to normal readings. The 40 hz appear randomly, 1 gen at a time, generators paralleled. All other data is accurate (volts, amps, kw). Below 80%, no problems. This happens on all 4 gens.

Is there a small filter available to clean up what xducers see? Is there another brand xducer that is not as sensitive to noise?

Any help would be appreciated (I am currently in the Gulf of Mexico on sea trials).

 

[itsmoked]

You can always try a snap-on filter. The kind you see on the cords to your computer monitors.

You can also ask the transducer maker as they have probably seen this before.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Marke]

Hello bb3030

The first thing that i would do, is ensure that the VFDs are installed in a manner to minimise the noise generated.

Make sure that the cable from the VFD to the motor is a screened cable with the screen bonded to the VFD chassis and to the motor frame. Pigtail terminations must be avoided.
Ensure that the screen is continuous all the way from the VFD to the motor.
The noise coupled into the frame of the motor needs to return back to the VFD and you need surface area on the earth conductor (screen) to provide minimum path resistance to minimise the noise voltage on the frame of the motor.

Best regards,
Mark

Mark Empson
L M Photonics Ltd