Re: Gecko wiring question

Two seperate points here.

1) Running the drives with supply voltages above 80VDC. The drives
are rated at a maximum voltage of 80VDC. The parts inside the drive
are rated at 100VDC. The drives come apart at 108VDC to 113VDC.

From 24VDC to 80VDC they will run for years. At 108VDC to 113VDC they
will die in microseconds. The point is as you go from 80VDC to 113VDC
the lifetime compresses from years to microseconds. How far into that
region do you want to be?

What you give up is margin when you operate up against the max limit.
A compressor or other large load will dump a surge on your 115VAC
line, running the motor into a stop or stalling at high speed will
dump energy back into your power supply. These events can add 20 or
more volts onto your supply momentarily.

At 24VDC, 48VDC or even 60VDC there is plenty of margin, at 80VDC
there is very little. At 80VDC the supply should be regulated and or
clamped to prevent overvoltage. Otherwise the odds of Murphy's Law
happening greatly increase.

2)There should be a compelling reason to run step motors at that
voltage. You must have an application where the highest possible
speed is of paramount importance. If that is not a requirement, it is
pointless to run them at that voltage. You should have a very good
reason when you give up reliability for performance.

Motor manufacturers like Pacific Scientific (the Mercedes Benz of
motors) and some others rate their motors for 65VDC maximum
operation. Why? Because more than that shortens the motor's life.

The drives have a diagnostic tell-tale that indicates if they have
ever been exposed to 100VDC or more. About 50% of the drives we see
returned for repair have.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Steven Ciciora
<sciciora@A...> wrote:

> The transformer is rated at 24VAC _at_ 10 amp load. With a 10A

load, the

> output should sag a little, getting it closer to spec.
>
> Also, the bridge rectifier only charges the caps at the peaks of

the sine

> waves. As soon as you start discharging the caps a bit, the

voltage will

> drop, because the caps will be discharging most of the time, and

only

> charging when the peaks of the sine wave are greater in voltage

than what

> is on the caps. Kinda hard to explain; easier to draw a picture.

If you

> looked at the loaded output of the power supply, it will look like

a saw

> tooth. A (somewhat) linear drop in voltage as the cap discharges,

and not

> a linear charge, but a shape that matches the peak of the sine wave

as it

> charges. Mariss posted a *.pdf file to the files section, with a

schematic

> showing how to automatically discharge the caps when power is

removed. He

> drew a nice picture showing what I'm trying to explain. If you put

a 10W

> 110VAC light bulb on the output, the voltage might drop, say, 3V.

Put a

> second 10W bulb on the output, and it might only drop 0.1V, etc.
>
> I'd like to hear what Mariss says about driving the geckos with

this setup,

> since he is the last word (warrantee wise) :-)
>
> Just a FYI...
>
> - Steven Ciciora
>
> At 09:34 PM 1/17/03 -0000, you wrote:
> >Well I started with 2 24V 10 amp transformers runn in series to

give

> >me 48 volts. but these are rated at 110 volts.
> >The power as measured in my shop is 122 volts. So I ended up with
> >29.5 volts per transformer or 58.7 (as measured) in series.