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James Newton
01-01-2013, 08:51 PM
This turned into a book, skip to the last paragraph for the real question.

I'm a little scared. I'm connecting an HP 6434B DC Power Supply. This is an old school boat anchor 40 volt 25 AMP DC supply. That is TWO FIVE AMPS at 40 volts or ONE THOUSAND WATTS. Direct Current. Maybe that doesn't scare you but I'm famous for my patented style of construction: Wonky Style. I'm a software / firmware / digital logic guy. I can manage analog electronics in general and I have good support on that from online friends. Physical construction? No. High power wiring? Not even a little bit. Hey, I'll plug in a 1500 watt electric heater and not worry about it, but I've seen what my style of wiring and a 12 volt 300 watt power supply can do (smells bad, burns things, turns black, etc...) so I want to make sure I do the wiring right. And this monster was damaged when it was shipped to me, (volt meter busted, and (-) banana plug and right handle sheared off) so I'm hoping I repaired it correctly and didn't miss any internal damage.

Once I got the front repaired, I thought I would just plug it in and see if it worked at low voltages / light load. But oh no, "one does not simply" plug in a 6434B. It has a /terminal block/ for the AC power cord!

The Manual says: "2-14 To protect operating personnel, (!!!) the National Electrical Manufacturers Association (NEMA) recommends ... this instrument should be used with a three-conductor power cable that has #12 AWG wire." The thickest appliance power cable I can find at the local hardware store is #14 gauge. Seriously? Do I have to order #12 gauge from online? Or drive to the next town?

It also says: "At 115 Volts, 60Hz, the full load requirement is 1300 Watts at 19 Amperes. The input power line should be fused for 25 Amps at 115Vac." We just had this addition made in 2009, and the wiring is up to California code for that time. The circuit breaker does say 25 Amps. Should be ok, no? Nothing else plugged in on that outlet except the spindle motor and an old PC.

On the output, the hookup wire I got is #14 guage... but I'll be running two sets of that, so it should be fine... right?

On either of those, the question is how to form the wire to make a secure attachment to the terminal block. That is where I really need help: What is the correct way to make a high power connection to a terminal block? I seem to remember the correct way is to make a loop in the wire, wrapping it around itself to form a "noose" then solder that to make sure it can't come apart, and finally, slip that around the screw and tighten it down. Yes? No? I can't seem to find anything on the net that says for sure. I can find lots of "wonderful" products and connectors, but isn't that wire loop the most direct, strongest, and least likely to fail or develop a resistance?

Al_The_Man
01-01-2013, 09:41 PM
Bit of a discrepancy between the input power and output?
It should be roughly the same?
But you can either use approved crimp tool with crimp ring terminals or use the method you described.
Al.

neilw20
01-02-2013, 08:48 AM
But you can either use approved crimp tool with crimp ring terminals or use the method you described.
Scared?
I've played with and used on a regular basis a 750v 40A DC supply. Now THAT is fun.
Not much smoke, but load bangs from time to time. Both hands in my pockets, and safety glasses.

James Newton
01-02-2013, 05:20 PM
Meh, 300 Watts loss between input and output doesn't seem bad when you are herding that much power. I can't imagine working with 30,000 watts! That is insane!

Anyway, I looped the wires and fired it up and it works! I'm jazzed!

neilw20
01-02-2013, 05:23 PM
Great. Just keep both hands in your pockets, or only use one hand.
Been doing that for years on 38KVA inverters.
It is all just a matter of scale.
The bang goes up as the cube of the power, it seems.

Al_The_Man
01-02-2013, 06:59 PM
It also says: "At 115 Volts, 60Hz, the full load requirement is 1300 Watts at 19 Amperes. The input power line should be fused for 25 Amps at 115Vac."

This is maybe where the confusion came in?
It is not clear if the 19a was output or input current?
Al.