Re: SLA7062 technical stuff - supply voltages

Very simple.

1) Get a 0.022uF/100V capacitor and a 15 Ohm/2W resisitor.
2) Put the capapacitor in series with the resistor.
3) Put the capacitor end to a winding output.
4) Put the resistor end to ground.
5) Repeat (1) thru (4) for all other winding outputs.

Mariss


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turyga1963" <TIntruder@...>
wrote:

>
> Mariss,
>
> Your info is very interesting!
>
> Would you be willing, if you have the time, to sketch out a drawing
> what it takes to construct a "snubber" and how one would add it to
> an existing stepper drive using a 7062?
>
> I think this would be a valuable accessory for those of us who have
> 7062-based drives and are operating with power supplies over 30vdc.
>
> Regards,
>
> Tom
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis"
> <mariss92705@> wrote:
> >
> > I hope nobody minds me sticking my nose into this.
> >
> > For fun I took a G201 and turned it into a unipolar drive by
> removing
> > the top MOSFETs in each full bridge. The motor center-taps went

to

> > the +supply, otherwise everything is the same. The drive actually
> > works that way.
> >
> > Run this way (kind of like an SLA7026 with 33A-rated MOSFETs) it
> > avalanches on each on-to-off output transition. The avalanche
> voltage
> > is 112VDC, the current is 3A and the time is 250nS. The energy is
> > 84uJ. This results in 8.4W dissipation due to avalanche heating.
> >
> > Avalanche operation should be avoided no matter what mfg.
> literature
> > says. Monolithic power ICs usually "pop" during that condition.
> >
> > I calculated an RC snubber to eliminate this behavior (I = 3A, V

=

> > 42V, 750nS time constant gives 15 Ohms and 0.05uF). The snubber
> was
> > built and applied to each output; it limited the voltage "spike"
> to
> > 12V.
> >
> > The SLA7062 claims 100V MOSFETs. This gives 44VDC as the absolute
> > maximum supply voltage (Vds = (100V - 12V) / 2). Throw in a sane
> > derating of 80% and you get 35VDC as the max rated voltage for

the

> > drive.
> >
> > These snubbers and 35VDC max should stop the "popped SLA7062"
> effect.
> >
> > Mariss
> >
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turyga1963" <TIntruder@>
> > wrote:
> > >
> > > Dave,
> > >
> > > You're right...I wish I hadn't spent so much time looking for a
> > > transformer that would supply those extra volts!
> > >
> > > I think this is valuable information, but I also wonder what

the

> > end
> > > effect is on how the steppers operate?
> > >
> > > If a board is rated to 42vdc and you supply only 34vdc or even
> > > 24vdc, what happens? If you still have the amperage, do the
> motors
> > > still turn as fast with as much power? If not, is the effective
> > > decrease linear?
> > >
> > > Tom
> > >
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> > > <dave_mucha@> wrote:
> > > >
> > > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turyga1963"
> <TIntruder@>
> > > > wrote:
> > > > >
> > > > > Dave,
> > > > >
> > > > > Good to know. Problem in my case and I suspect that of many
> > > others
> > > > > who have had similar problems is that we were expressly

told

> by
> > > HCNC
> > > > > that we could use up to 42vdc and the circuit board is even
> > > > > silkscreened to show that voltage. Further we were told the
> > > closer
> > > > > to 42vdc we got, the better as that would insure maximum
> > > power/speed
> > > > > from the steppers.
> > > > >
> > > > > Oh well, live and learn...
> > > > >
> > > > > Tom
> > > >
> > > > I found that many of the parts seem to fit well with existing
> > > > transformers.
> > > >
> > > > a 24V transformer times 1.414 to get 34 volts fits well to a
> 44
> > > volt
> > > > maximum unit.
> > > >
> > > > 48 volts to the Gecko offers about 66 volts to the drive.
> Again a
> > > > nice fit without leaving too much room for improvement.
> > > >
> > > > Some time ago, Mariss posted some results of life expectancy
> of
> > his
> > > > drives. at 114 volts the life expectancy was something in

the

> > > minutes
> > > > range. at 80 volts it was in the years, at 90 it was in the
> > months
> > > > and only got worse as the voltage increased.
> > > >
> > > > I suspect that this is the case with all drives. there is a
> sweet
> > > > spot that offers a very long life and a bleeding edge where

one

> > > > mistake, one time results in that sinking feeling you get

when

> you
> > > > smell that magic smoke.
> > > >
> > > > Dave
> > > >
> > >
> >
>