Episode #11: How To Select A Mains Filter

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The Motion Control Show

I am continuing my conversation with you about EMC installation. We talked about electrical noise, where it comes from and how we control it. We talked about the reasons for Mains filters. Now I'm going to talk a little bit about how to select Mains filters and unfortunately, it's a real black art.

I'm Corey Foster.  Let's talk about this.

Really quick review on the reasons for Mains filters. It is for EMC compliance. We might have electrical noise issues and so of course we want to reduce that electrical noise problem. That's the purpose for the CE(EMC) compliance. There might be bouncing sensors and feedback problems. We want to protect against that electrical noise input, from the environment. Your system may work in a clean environment in the lab, but once you get to the end location, maybe your customer site, there's external environmental issues that you may not be able to control: welders, VFD’s, pumps, HVAC systems etc.

fig 1 electrical noise
There are a few different approaches. You can put your system together, take the shotgun approach.  Does it work?  Maybe, maybe not. By suggestion: we can suggest a Mains filter to install that has come from a previously successful combination. We can do some spot checking, we can use an oscilloscope scope, or even use a multimeter in some cases. An oscilloscope is better because it can give you a trend over time as shown here. On the top, you have a nice clean ground, on the bottom you have a dirty ground. You could also take some real measurements. You can have a CE certified specialist come, a consultant come in. I have a couple different sources if you want to you know some suggestions.  Reach out to us at Valin.

There are some considerations for Mains filters: the voltage, the current, the leakage current and, in all these cases, particularly the leakage current, there's the good better or best. There's something that is good enough or there's something that is really the best one out there.

At least one Mains filter manufacturer that I know of will give you a suggestion on a model number based upon the drive manufacturer. Manufacturer One in a single drive application, they'll give you a Mains filter part number A. If you have multiple drives, they will give you part number B. A different manufacturer, they'll give you part number B for one drive and part number C for multiple drives. For each manufacturer, they will have different suggestions based upon completed tests. Often times these tests are in their labs, other times they're out on customer sites. They've made these measurements and they've found what worked in those situations.

fig 2 electrical noise
The question is, why can’t we make a more definitive answer? For those of you have kids, this makes sense. Not everything you do to raise one kid will work for another kid. In fact, what works for you won't work for another family and vice versa. Even though drives are the same technology, they are not designed in the same way.
I have a unique situation where I have identical twin boys. We had them DNA tested to verify that, yes, they're identical twins. When you have kids, you always wonder is that the DNA or is it the environment? Just like a drive, is it the way it's designed or is it in the environment? The answer is, yes, it's really both. My kids are identical twins. They look a lot alike as you can see here. Other times they don't look very much alike. As they’ve grown, sometimes they look alike and other times they don't. The environment really does have an impact on the drive and technology and how it interacts with the environment around it, just like people. You must take the environment into account when you are installing your drives. Just like when you're raising your kids. They have their own personalities even if they're designed the same way.

If you have any questions and are wanting to know more, reach out to us at (855) 737-4716, or fill out our online form.