Gentlemen,

There is a lot of fog and theories about Variable speed drives creating stray voltages and causing problems to cows in dairy farms.

I know cows are sensitive to stray voltage, but do VSd's cause such voltages ?.

What are the methods to avoid/measure these voltages?

Any thoughts/ideas are appreciated.

Hi chaterpilar

This a definite fact and the problem can be minimized by the correct installation of the correct VFD.

The VFD generates a high voltage high frequency carrier on its output terminals. This is connected to the motor and the high frequency currents can leak in all directions.

There are a number of steps that can be taken to minimize the problem, but the first is to ensure that you start with a good drive that is easily able to comply with the European EMC requirements. Some of the cheaper VFDs just can not be quietened down sufficiently.

I have a page on installing VFDs in irrigation installations for minimum EMC and these steps are exactly the same in cowshed applications. see http://www.lmphotonics.com/vsd/vsd_05.htm

If you have any further questions, ask them here.

Best regards,

Thanks Marke for the reply. The link is very informative.

I tried to post a question there but it directed me here.

Just one thing more...What is the best way to measure stray voltage at say a Stanchion..?

Found this link very informative also..

http://www.emfrelief.com/stray.htm