Newbie- Power supply step down? Gecko high voltage?

[bead]

I have a 80v 12amp power supply from Antek
http://www.antekinc.com/details.php?p=324

I got it for the Keling steppers I have which I was told take 80V
http://www.kelinginc.net/KL23H286-20-08B.pdf

I am using Gecko 203Vs so they should be able to handle the voltage I think?

Also, what is the simplest way to step down the voltage from this power supply? The only thing I could think of would be to get another transformer and put it on the output side of the toroidal transformer before the full wave bridge and filter capacitors.

What do you guys think? Thanks for the help.

[H.O]

The G203's are specified to handle 80V max, so you're right on the limit. They won't instantly turn into vapor if the voltage gets to 81V, there's a bit of headroom built in, but a surge on the mains at the same time as you decelerate an axis (or two or three) MIGHT push it above its destruction point. I'm not saying it will I'm saying you're on the limit.

The motors inductance is 6.8mH in parallel and Geckodrive recommends no more than 32*(SQRT Inductance) or 83V in this case so again, you're are really at the top of the spectrum.

The best aproach to lower the voltage is probably to get a new powersupply. Another option (probably just as expensive as a new supply) is to power THIS supply with a variac, that'll let you adjust the output voltage.

Finally you can either remove a couple of turns of wire from the secondaries (same number of turns from both windings) or you can wind some more turns on "in reverse" to lower voltage but don't mess with this if you don't know what your doing.

You can also add a power dump circuit which loads the supply when the voltage gets above a certain limit but since you're right on the limit here it can get a little tricky. OR you could add a crowbar circuit, it's "a bit" more brutal in that it simply shorts the supply out, blowing its fuse if when the voltage rises above its set limit.

If you're worried, try talking Antek into replacing your supply with a lower voltage one or sell it and get another.

Good luck!
/Henrik.

[bead]

Thank you for the reply!
I will look into what Antek says about possibly trading my transformer for a different one.

I also might get some lower voltage motors too, those might be harder to send back. I've never used them however, but we will see. I know the motors are kind of high voltage, I made a newbie mistake when I was buying this. I don't know what kind to get now. Maybe some good bipolar 40 some volt ones from Keling.

[bobsch]

power THIS supply with a variac, that'll let you adjust the output voltage.

Don't mistake a light dimmer for a variac. They aren't the same thing and a light dimmer won't work. They are usually limited to 600 watts and don't like inductive loads, like anything with a transformer.

[Al_The_Man]

That the beauty of the Toroidal transformer, it is very easy to tailor by removing turns, approx 2t/volt, or adding a small auxiliary winding for 5 ~ 24v etc.
There are quite a few previous post on explaining it.
Al.

[bead]

Originally Posted by Al_The_Man That the beauty of the Toroidal transformer, it is very easy to tailor by removing turns, approx 2t/volt, or adding a small auxiliary winding for 5 ~ 24v etc. There are quite a few previous post on explaining it. Al.

Could you perhaps direct me to a post on it? It would be really great even if it was a Antek torrid but they are probably all made the same way.

[bead]

I was talking to someone at work here and he suggested maybe wiring it as if I was going to run it on 220Vac but still plug it into 110. Would that effectively cut the output voltage in half?

Would this be safe to do?

[Al_The_Man]

Safe, but not quite so efficient, it will change the VA rating.
I use Antek and modify all the time to get the actual secondary I want.
Here is one of many links if you search Toroidal.
http://www.cnczone.com/forums/showth...oroidal&page=2
Al.

[Mariss Freimanis]

The G203V has a healthy supply voltage derating. It's rated at 80VDC, designed for and tested at 100VDC and it doesn't come apart until you hit 116 to 118VDC. Avoid going over 80VDC if you can but nothing terrible will happen at 81VDC. There is about a 36V safety margin, going over 80VDC eats into that margin. Here's the reason for it:

1) Line voltage goes to the +10% tolerance; 80VDC turns into 88VDC.

2) Rapid deceleration returns energy to the power supply; 88VDC turns into 98VDC. This applies to single axis systems. There is no voltage rise when multiple axis are powered by a common power supply.

3) A load dumps to the mains (air compressor, etc.) and the shop lights brighten for a half second. 98VDC turns into 108VDC.

It's just Murphy's Law; if it can happen, it will happen. All 3 things happening simultaneously can turn 80VDC into 108VDC for a half-second. The G203V will shrug it off like it never happened with a nominal 80VDC supply. At 88VDC nominal your results could be unhappily different.:-)

Mariss