[snakebit95]

Al,
I do not have any mounting around the perimeter of the transformer. I machined a mounting support boss from nylon, to support the weight for a vertical mount. I attached a photo.

[ViperTX]

Do you have a schematic of the input and how the secondary is wired...

[Al_The_Man]

I think you are going to need a bit of instrumentation and log/find out what is happening, not only on switch on, but normal running.
Do you have access to someone who has at least a clamp-on amp attachment (below), preferably one that can capture peak as well as display normal.
I tried my 1kva DC shop power supply, powers up with both AC & DC.
The inrush was just detectable and the running no-load barely shows on the meter.
Al.

[lerman]

Most toroidal transformers I've come across like these have dual windings on both the primaries and secondaries. They may be connected in either series or parallel.

If you have the secondaries connected in parallel with the windings reversed, I believe that will act like a short circuit. Also, make sure you know which wires are which. Connecting a low voltage secondary across the line would be a problem. Connecting the two primaries in parallel across a 220 volt line would also be a problem.

I would suggest you proceed as follows:

1 -- Disconnect all of the secondaries. See what happens.

2 -- If there are multiple primaries, disconnect one, and connect the other to 120 volts. See what happens.

Report back.

Ken

[snakebit95]

I think you are going to need a bit of instrumentation and log/find out what is happening, not only on switch on, but normal running.
Do you have access to someone who has at least a clamp-on amp attachment (below), preferably one that can capture peak as well as display normal.
I tried my 1kva DC shop power supply, powers up with both AC & DC.
The inrush was just detectable and the running no-load barely shows on the meter.
Al.

Al,
Thanks for taking the time to test your 1kVA transformer. That tells me there is definitely something wrong on my end. I can borrow a scope from work, but it will be Tuesday before I get that chance due to the holidays.

Just for grins, I disconnected EVERYTHING and wired the transformer directly to the 110V outlet (but included the main power switch and the fuse ahead of the transformer). It popped another fuse. I am starting to wonder if there is a short in this transformer. Before I ever started this thread, I called Hammond to verify that I had it wired properly; and they confirmed that I did. I explained my problem to the tech, and he stated I probably needed a high magnetics breaker to address the in-rush issue. That did correct the breaker issue, but now the problem moved to the fuse block. I have a smaller transformer (870 VA) that I may try installing today to see if the problem persists.

Viper,
I do not have a wiring schematic, but will try to sketch something by hand today and scan it in. I am a mechanical guy, so my sketch will be pretty crude - LOL. To give you a bit more background, I simply moved this control system from a smaller working machine that did not display any of these issues. The only difference this time, is a larger power supply (i.e. larger transformer, rectifier and cap).

[Al_The_Man]

Its too bad you can't at least get past the initial inrush stage, because if there is also something else causing a high current, after a few minutes, something would be getting VERY warm!
Al.

[snakebit95]

Al,
I may have figured it out!! I pulled the tranny from the box and connected it directly to the outlet (no fuses or main switch) and it powers-up just fine. I did it numerous times without popping any breakers. However, I did notice a slight flicker of the lights each time I switched it on. The small rubber insulation pad seems awefully thin and small in diameter. Is it possible one of the windings was arcing or touching the mounting plate and creating a short-circuit? I do not see any electrical burns to indicate so, but it has me wondering. I am on my way to Lowes to pick-up some more fuses and some thicker rubber sheet (if I can find some) to make a larger insulation pad.

[Al_The_Man]

Al,
. However, I did notice a slight flicker of the lights each time I switched it on. The small rubber insulation pad seems awefully thin and small in diameter. Is it possible one of the windings was arcing or touching the mounting plate and creating a short-circuit?

Flicker is normal.
It had crossed my mind at one point that maybe something had been pinched or wires had been forced together if you reefed it a bit hard on to the the base.
I would inspect the underside closely before re-mounting.

At least now you can enjoy your Christmas
Al.

[Bloy2004]

Heh! ...not that anyone is here now....the night before christmas...but,

to mount my "heavy" toroid I took some of that clay-like caulking, rolled it into a rope, made a circle to fit under the tranny. I plopped the tranny on it and put a mounting bolt up the middle through the temporary base. I mixed up a batch of "bondo" and oozed it down the throat of the tranny surrounding the bolt and filling just a bit more that half way up to make it self secure. The putty ring held it from getting out. Once solidified the tranny had a nice "saddle" under it and a hole through the middle to mount.
Then just used an appropriate flat washer to secure the tranny.
The bondo under the tranny gave equally distributed pressure all around the bottom for gravity, and the nut /washer just held the bondo.

This I did to ensure there were no forces pressing on the coils to cause a possible internal short.

By the way, Al-THE-Man guided me through rewinding the beast!

[snakebit95]

Just a quick update to let everybody know the power-supply is now working correctly. Evidently it was shorting to the mounting plate when I clamped it down. I want to thank everybody for their help with this problem. Your suggestions forced me to dig a bit deeper and find the solution. Thanks again and I hope everybody has a MERRY CHRISTMAS!!!

Bloy.........Thanks for the laugh!! There is no way I would have ever thought of using bondo to mount the tranny. I guess if everybody in the world thought the same.......the world would be a boring place

[Tig]

Hi Haydn,
Great looking PS. I just ordered a couple of NTC surge limiters for a PS I am assembling. Could you elaborate a little more on your relay setup. Is the switch integral to the relay, and could you elaborate further how you wired it with the E-stop.
Thank you for your time.

[Tig]

Hi,
Another question regarding inrush current suppression.
I was just wondering: if one was to stick the Inrush Current Limiter on the primary side of a 220V:120V, 3KVA Industrial Control Transformer, why you need only one NTC. It seems odd if both of the feeds are energize. The sales person at Ametherm said to use only one. Can you explain to me why only one NTC is required.
Another question if I may. Is there any reason why the bleeder resistor must be in the circuit all the time. Why not just dump the capacitor charge to a resistor on shut down via a DPDT main power switch, and or switch that could close during loss of power.
As always thank you for your time.
Tig

[pastera]

You need only one inrush limiter because it is in series with the transformer.
A time delay relay that shorts it out after power up will allow the limiter to cool down and be ready for immediate reapplication of power.

The bleeder resistor can be hooked up to a relay that will connect it at power down - it can then be a much smaller wattage as it will only dissipate for a very short time.

Aaron

[Haydn]

Hi Haydn,
Great looking PS. I just ordered a couple of NTC surge limiters for a PS I am assembling. Could you elaborate a little more on your relay setup. Is the switch integral to the relay, and could you elaborate further how you wired it with the E-stop.
Thank you for your time.

I will try and getting something up by the weekend.

[Haydn]

You need only one inrush limiter because it is in series with the transformer.
A time delay relay that shorts it out after power up will allow the limiter to cool down and be ready for immediate reapplication of power.

The bleeder resistor can be hooked up to a relay that will connect it at power down - it can then be a much smaller wattage as it will only dissipate for a very short time.

Aaron

Thats exactly how mine is done.

[Tig]

Thanks Haydn,
I will look forward to it.