Re: [CAD_CAM_EDM_DRO] Re: Gecko G201 and Drive Current ?

Yes I'm sure. It's regulated at 36 Volts and can deliver (tested) 9 Amps.
At 9Amps the voltage is 35.9 ... it's solid supply.
Hans W


"ballendo " wrote:

> Hans,
>
> Are you sure your power supply is doing its job?
>
> Ballendo
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Hans Wedemeyer <xyz@h...>
> wrote:
> > Jon,
> > The clamp-on amp meter is DC only, range FSD 0-1mA(one milliamp)
> through 0-10Amps
> > The old HP 428 is one of the few oldies (tubes) I keep around
> because it is so handy.
> > Calibration is easy to check and it is good.
> > Here's one for sale on eBay http://cgi.ebay.com/ws/eBayISAPI.dll?
> ViewItem&item=3308854547&category=4678
> >
> > I did the current shunt, simply placed it in the 0V return total
> power supply. As the resistor is
> > very low in value 0.027 Ohm I figured it would not influence the
> overall performance that much, and the results are the same
> > resisitor in circuit or not.
> > My first measurement was wrong (posted earlier results) as the
> signal across the 0.027 Ohms is so low
> > and there is a lot of switching noise, I missed what appears to be
> steps in the wave form.
> > The new reading appears to be about 0.1V pp which would indicate a
> total circuit current of about 3.7 Amps.
> > I suspect the 3.7 Amps total should be divided by 2 (two windings
> being driven) which would make the per winding current
> > about 1.6 Amps.
> >
> > I have a 15,000uF Cap. at the Power input of the Gecko (6 inches
> from it), total power lead length is 3 feet. Power unit is regulated
> 36 Volts 9Amp.
> >
> > The motor specs. are Current/Phase 5.6 Amps, Phase resistance
> 0.39, Inductance 4.1mH
> >
> > All measurements are taken with motor running. When the motor is
> OFF the disable feature is active and winding current is reduced.
> >
> > One last thing that may shed some light on what's going on.
> > I have zero experience with the Gecko modules, and based upon all
> the massive heat sinks everybody seems to be selling for them, I
> assumed at 5 Amps the Gecko Module should at least be warm... well
> > it's cool to the touch and I only have a small 6" x 6" x 0.065"
> heat sink during this initial testing phase.
> >
> > As my tests are under my control, I'm able to ensure there is no
> over heating. I wish there was some heat ...that would indicate some
> Amps are flowing..!
> >
> > I this ever works, final heat sink will be the case of the device
> which is 0.375" think and has a surface area of over 4 square feet !
> That should be enough to keep the Gecko cool....
> >
> > Any more suggestions would be welcome. In the mean time I'll work
> on measuring AC current in a winding.
> > Best regards
> > Hans W
> >
> >
> > Jon Elson wrote:
> >
> > > Hans Wedemeyer wrote:
> > >
> > > >Here's my setup.
> > > >Gecko G201 and PACSI H32 Series motor parallel wired to take 5.6
> Amps.
> > > >Gecko has a 120K Current set resistor this should be a 5 AMP
> setting.
> > > >DC Supply 36 Volts able to supply Max 9 Amps.
> > > >Length of cable from Supply to Motor 3 feet. 14 Gauge Wire .
> > > >15000uF Cap. at the Gecko module.
> > > >
> > > >I did not get the power I expected. This motor is rate at 445oz-
> in and the project was calculated to
> > > >need about 160oz-in.
> > > >
> > > >When it failed I started to investigate. First I used a clamp
> on Amp meter on the Plus Output lead of the PSU
> > > >
> > > Does this clamp-on meter read DC? Most don't. I suspect it is
> reading
> > > the current peaks
> > > of the chopping action.
> > >
> > > >and started the motor. It read 1 Amp ! I know the reading is
> integrated, but I really did expect it to show at least 2-3 Amps.
> > > >
> > > >
> > > Not necessarily. Your motor probably has a resistance of 2 Ohms
> or less
> > > per winding.
> > > 5.6 A x 2 Ohms = 11.2 Watts per winding, or 22.4 W for both
> windings.
> > > neglecting
> > > switching and other losses in the Gecko, with a 36 V supply, you
> only
> > > need I=P/V =
> > > 22.4/36 = .622 Amps when standing still! Do you have the local
> > > capacitor that is
> > > supposed to be placed at the power input terminals when the main
> > > capacitor is several
> > > feet away?
> > >
> > > >This makes me suspect the Gecko.
> > > >
> > > >Does anyone have a good method to confirm the Gecko really is
> switching these windings at 5 Amps ?
> > > >I have equipemnt to test... just tell me how to test this :-)
> > > >
> > > >
> > > You need a low-inductance current shunt or a Hall effect clamp-on
> > > current probe to measure
> > > pulsed currents like this. a low-inductance current shunt can be
> made
> > > from 10 1 Ohm 1/2 Watt
> > > resistors in parallel. This will have a resistance of .1 Ohm at 5
> > > watts. You can use this with
> > > a DVM, or better with an oscilloscope. But, with the scope, you
> need
> > > isolation, as the
> > > motor outputs of the Gecko are not referenced to ground.
> > >
> > > Jon
> > >
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