Dear Friends,
We have a large piece of lab equipment that uses 3 vacuum pumps and
several power supplies. The controllers for the pumps are stand alone
type, fully encased. We take these controllers and power supplies and
install them inside our equipment.
The problem that we have is that the controllers and some of the power
supplies have their own EMI filtering. This causes the leakage current
of each one to be between .5 mA and 1 mA, well within the limits. But
when we install them inside of our end product, these add together
with the EMI filters of the end product to create a high leakage
current of 6 mA. (We are using EN 61010 clause 6.3.2.2, and these
values are measured with the ground wire open.)
I see 3 possibilities, but could use some feed back, as "there is
wisdom in many counselors".
1. The controller manufacturer has stated that we could isolate the
ground path to the Y caps in their unit. The draw back here is the
modification of an approved component.
2. Change from a detachable line cord to a permanent wiring scheme,
and provide another ground wire. So in the event the ground wire in
the line cord breaks, there is another ground path. Although I've seen
this, I can not find any reference to this construction in EN 61010.
3. Provide multiple line cords. I'm not sure this will work because of
the disconnect requirements.
Thank you for your thoughts on this issue.
Regards,
Ray Russell
ray_russ...@leco.com
