INSULATING CHOKES AND MODULATION INDUCTOR'S ABOVE GROUND

[W2PFY]

Who said ePay ain't good for nothing? Well I came across this today and it shows a nice way to bolt down your iron with a tiered layout. In the past I would just put them up on something and hope for the best that an arc over wouldn't occur. Nowadays you can go to Home Depot or Lowe's and get large size plastic screws to anchor your iron to the cabinet if your in an earthquake zone, or anticipate a move somewhere in the house or a new QTH to hold them in place.

Now all I need to do is get back my insulation materials that are currently at another's  QTH and get to work!

A word about safety, before touching iron above ground, please be sure to alligator clip them to ground! Don't forget to unhook your grounding devise before re-energizing the circuit!

Hope this helps!  

[w7fox]

Excuse my ignorance, but why would you want to insulate a transformer?  I always make sure there is good safety ground attached to the core.

Yours inquisitively,
Fox, W7FOX

[W2PFY]

Excuse my ignorance, but why would you want to insulate a transformer?  I always make sure there is good safety ground attached to the core.

Yours inquisitively,
Fox, W7FOX

Well Fox, many of us have been doing that for years. Some may feel that it is not good engineering practices but this is ham radio. As an example, I just found a beautiful RCA modulation transformer that is probably 80 years old. There is no name plate rating on the voltage the winding's are rated at to the core or from primary to secondary. By mounting it above DC ground there is less a chance that it will create a current path to its core and save it from an early trip to the scrap yard  

In the case of a inductor where you needed one at 1 amp at 4 KV and you don't have it, but you do have one rated at one amp at 3 KV, I would use it in the 4 KV circuit above ground.

I have a nice 11 Henry choke that is rated at 6 KV but it has leakage to the core in the order of a few meg ohms. For whatever reason, heating it up to hopefully drive out the moisture (if that is what it is) didn't work. I ended putting it in the negative lead of a full wave power supply and that solved that problem. But there is another part of the story about that inductor, it is a modulation reactor complete with spark gaps and it really a waste using it the way that I am so, one day it  will come out of that service and mounted above DC ground to gain use for it's intended service.  

I am sure there are many others on here that have done the same. I even heard of people just putting their iron above ground using ordinary dry lumber.

Generally speaking,  high voltage power supplies are very dangerous and I just cannot see any additional danger putting components above DC ground, when one should consider that it is NEVER a good idea to stick your hand in there to measure temperature of a given component as an example. One thing for sure, I would never mount a plate transformer above ground! That could get ugly very fast!

I hope this explains this a bit more and I hope others will chime in!

Terry  

[Opcom]

I agree with Terry. The modulation transformer in the big AM set here is from the 1940s. It was rated for 3000-3300V and is run around there, sometimes a little more. Rather than risk blowing it due to its age and physically decrepit condition, it's bolted onto 2x2 wood strips, sits on them. The strips are bolted through the 1/2" plywood floor to the high strength metal floor of the cabinet. There could be a very slight leakage but no direct short. Dry wood is important. Lot of people do this as a preventive measure because those parts are expensive.

[KD6VXI]

I have a Henry 2k xformer that has leakage from one terminal to ground.

It Noah's a nice sticker on it that states it's floating and at B+.

Transformer works just great,  but the case sits at about 300 volts above neutral.

Micarta sheets and Glastic insulators are your friends.

--Shane
KD6VXI

[KC4VWU]

I've been told hardwood 1x1's, and some have said to soak them in paraffin to resist moisture. Bob Sullivan gave me 1x1's of hardwood when I got the BTA-500R from him. IIRC, the bottom of the tx. didn't have any holes in it to mount the iron, so it just sat in there.

[KB2WIG]

Plasteek cutting bordes are cheep and easily worked. Yew can counter sink mounting boltes fer yer heavy iron, and then mount the plasteek bored onto yer ply wood. It will sit like a bug in da rug in yer rack .....  The Derb would be proud.


KLC