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Re: [TCML] Testing a line filter



I can tell you from personal experience that a small (20 amps or less rating) EMI filter at the input to a motor (RSG drive or cooling fan) indeed does seem to offer some protection to the said motor. I burnt up a few RSG motors in my early days of coiling, but have not had a single  motor ‘mishap’ since employing an inexpensive EMI filter at the input of the motor.

Now as far as using large (and more pricey) EMI filters at the input of the power transformer to block the nasties from the coil from finding their way back into your house wiring...I would concur with Gary’s thoughts on this matter, even though I too have (and still do) use them extensively.

David

Sent from my iPhone

> On Feb 27, 2019, at 5:17 PM, Gary Lau <glau1024@xxxxxxxxx> wrote:
> 
> Testing the attenuation of a line filter would be challenging, especially
> since there is no consensus for what it is that the filter is supposed to
> do.  Filter the resonant frequency of the coil (too low, not likely)?
> Filter VHF transients from the spark gap?  How do you measure that?  Filter
> high voltage spikes?  Not the job of an EMI filter!  But considering that
> the price for a new filter on the surplus market is just a couple of bucks,
> just get a new one!  I used such a filter because they're dirt cheap, but I
> harbor no illusions that it makes a measurable difference in anything.
> 
> Gary Lau
> MA, USA
> 
>> On Wed, Feb 27, 2019 at 1:44 PM Daniel Kunkel <dankunkel@xxxxxxxxx> wrote:
>> 
>> Hello list,
>> 
>> I recently exceeded the 20 amps of a commercial line filter. I don't think
>> I let the magic smoke out, but is there a way to verify it is still
>> working? I am thinking of just using a signal generator and oscilloscope to
>> see how much it is attenuating.
>> 
>> Thanks,
>> ~Dan
>> Kansas City area
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