Re: [TCML] Terry filters

[resonance@xxxxxxxxxxxx]

If you are really on a tight budget using used NSTs and can't afford a
full Terry filter, there is an alternative.

For almost 20 years I used a simple pair of air core RF choke made of 2"
ID x 12 inch long PVC tube.  I wound it for 10 inches with #26 AWG PVC
covered wire.  It seemed to catch especially the very nasty high freq
transients that could break down the NSTs HV coils as these transients can
form a "spider-web" like effect, essentially "crawling" over the windings
until they connect and then the main power flows causes failure.

Using a pair of these simple air core chokes I had only one failure in
nearly 30 years.  Some of these coils with NSTs and these simple chokes
are still in daily operation at museums for over 15 years.

The failure I had was also a used NST so that could have entered into the
factor --- the xmfr might have been ready for a failure from prior neon
service.

Food for thought anyway.

Dr. Resonance




> Hi Neal,
>
> Yes, there are losses with a Terry Filter. It is a trade off for
> protection. It is also specific to center grounded transformers
> primarily NST's due to their fragility. It is a one size fits all for
> NST's for most of the components except the MOV's. When were using
> MOT's, PT's, PIGs, etc.. there is no such filter added other than basic
> mains filtering. Terry Filters are not a big loss, but there is some.
>
> The problem is that NST's can't handle to much voltage over their
> ratings (were using NST's for something quite different then they were
> designed). Most NST deaths are due to one of the secondary windings
> being over-volted near the outer turns. NST's are also a pain in the but
> to fix due to the potting compound. So a little protection does help
> even with some minor filter losses.
>
> Take care,
> Bart
>
>
> Neal Namowicz wrote:
>> Hello everyone,
>> Just a question about terry filters, since the topic seems to be
>> cropping up a lot lately. How much loss is there when using them? I'm
>> no EE, but any time I see the main power coming in going through
>> resistors, there must be some loss. Also, are the TF's "one size fits
>> all", or can the components be sized to correspond with how much
>> potential power you have coming in? It seems that we endeavor to
>> eliminate "lossy" components. "Using beer bottle caps? Replace them
>> with an MMC." Don't use a dimmer switch, too "lossy", etc. Ultimately,
>> is using a TF a trade-off between loss and protection? Kind of like
>> driving a newer car that comes with a mandatory explosive device (air
>> bag) in the steering wheel. "But it's for your protection!" Just one
>> of a number of reasons my two vehicles are 1964 and 1980 Chevys. The
>> k.i.s.s. principle, and no bombs staring me in the face. But I
>> digress, sorry. So, what do you think about the terry filters?
>>
>> Neal.
>
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Dr. Resonance

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