Re: Here's my proposed power supply setup.

Lloyd,

You can use a bleeder if you want to but the drives themselves are
a "bleeder" load. They will rapidly discharge the capacitor to around
12-15V before they shut off.

You have to work very hard to get shocked by voltages less than
80VDC. It may tickle a little bit but that's about it.

For saftey reasons (fire), I would definately switch the 115VAC going
into the transformer.

Any fan and heatsink combo that keeps the drives cool is fine.

Mariss

--- In CAD_CAM_EDM_DRO@y..., "Lloyd Leung" <lloyd@l...> wrote:
> Thanks for the corrections Mariss, it's much appreciated. I now
> understand the major parts of this power supply.
>
> However, there are still a few questions I have...
>
> I purchased is a switch that breaks the connection for both AC wires
> (switches on/off for both wires from the AC in), is this a good
idea? I
> know that the capacitor will act like a battery if I use this kind
of
> switch, as the power will have no were to go. To alleviate this
> potential shock hazard, I will put a bleeder resistor on it. I
> currently have two bleeder resisters - 620ohm 10W, and a 500ohm 5W.
> Which one should I use or does it matter, or should I go out and get
> something else?
>
> If this is a bad idea... how should I implement a switch to power
on/off
> my power supply?
>
>
> Also, what type of computer CPU Fan was good to use with the Geckos?
>
>
>
> Thanks.
>
> Lloyd
>
>
>
> -----Original Message-----
> From: mariss92705 [mailto:mariss92705@y...]
> Sent: August 16, 2002 4:13 AM
> To: CAD_CAM_EDM_DRO@y...
> Subject: [CAD_CAM_EDM_DRO] Re: Here's my proposed power supply
setup.
>
> Lloyd,
>
> Couple of small errors. The 1/3, 2/3 business refers to the current
> drawn from your power supply, not what you set the motors to. Use
the
> name plate rating (3.5A for the Shinano motors, 3A for the Vexta
> motor) if you plan to run them in parallel or half winding. Use
half
> of that current (1.75A and 1.5A) if you plan to run them in series
or
> full winding.
>
> Adding all the currents gives you 13.5A. 2/3 of that is 9A. That is
> what your supply has to provide. It is the same regardless if your
> supply is 24VDC or 72VDC. 72VDC is the practical maximum voltage
for
> an unregulated supply because the output voltage tracks the line
> voltage which has a +/- 10% tolerance. At +10% your 72VDC would
turn
> into 79.2VDC.
>
> Calculate your capacitor size as uF = 80,000 * I / V. At 24VDC the
uF
> is 80,000 * 9 / 24 or 30,000 uF; at 72VDC uF would be 80,000 * 9 /
72
> or 10,000 uF. Your choice of 4,700 uF is not enough.
>
> To your questions:
>
> 1. The higher the voltage, the faster the motors will run. That
comes
> at the expense of having much hotter motors no matter the speed you
> actually run them at. Use a voltage sufficient for what you need
but
> not greatly in excess of that. If you have a mix of motors where
some
> have to run fast and others do not, wire the slow ones in series.
> They will not get as hot then.
>
> 2. No other issues except for what was covered above.
>
> 3. A bleed resistor is not particularly important. The drives will
> bleed it down quickly all by themselves. Use my "power supply
> circuit" in the files section if you intend to operate near the
> maximum end of the supply voltage range.
>
> 4. Whether running or not, if 4 motors are powere up, all 4 will
draw
> current. Use the above calculations for the supply.
>
> 5. Nothing special here. Use a single transformer if you can. It's
> simpler that way.
>
> 6. Covered above.
>
> 7. Power is RPM times torque ( W = RPM * in-oz / 1351 ). Doubling
the
> supply voltage doubles the speed to which a given torque can be
> maintained. At a given voltage, the parallel connection gives twice
> the power as a series connection.
>
> Mariss
>
>
>
> --- In CAD_CAM_EDM_DRO@y..., "Lloyd Leung" <lloyd@l...> wrote:
> > I just want to get my numbers and logic correct. This is my
plan,
> and I
> > would like to hear any comments, objections, errors or omissions
to
> this
> > setup.
> >
> >
> >
> > I've got three Shinano Kenshi steppers (4.2VDC, 3.5A) [8 wire],
and
> one
> > Vexta stepping motor PK296-02AA (3A, 1oHm, documentation says 3V)
[6
> > wire]
> >
> >
> >
> > Which means I should be powering my steppers somewhere in the DC
> voltage
> > range of 16.8V to 105V (Shinano Kenshi), and 12V to 75V (Vexta);
> this
> > range is obtained from multiplying the motors sticker voltage by
4
> (low
> > end) and 25 (high end).
> >
> >
> >
> > The operating range of the Gecko G201 overlaps with the voltage
> ranges
> > found above. So running the gecko g201s somewhere between 24VDC
and
> > 75VDC should not be a problem.
> >
> >
> >
> > The current/amperage setting should be 2/3 of the current rating
on
> the
> > drive if ran in parallel - 1/3 of the current rating if ran in
> series.
> > [www.geckodrives.com]
> >
> >
> >
> > Here's what how I'm going to hook it up [hope the formatting
stays]:
> >
> >
> >
> > Step down transformer; 120VAC to (between 17VAC and 57VAC)
> >
> > - Bridge rectifier (gives me voltages between 24VDC and 80VDC)
> [above
> > range multiplied by 1.4]
> >
> > - 4700 (four thousand seven hundred) uF capacitor (100V)
> >
> >
> >
> > - 5 AMP fast blow fuse
> >
> > - 470 uF (100V) (Z Axis)
> >
> > - Gecko G201 (set at 2.3 A parallel or 1.2 A series)
> >
> > Shinano Kenshi stepper (4.2V, 3.5A)
> >
> >
> >
> > - 5 AMP fast blow fuse
> >
> > - 470 uF (100V) (Z Axis)
> >
> > - Gecko G201 (set at 2.3 A parallel or 1.2 A series)
> >
> > Shinano Kenshi stepper (4.2V, 3.5A)
> >
> >
> >
> > - 5 AMP fast blow fuse
> >
> > - 470 uF (100V) (Z Axis)
> >
> > - Gecko G201 (set at 2.3 A parallel or 1.2 A series)
> >
> > Shinano Kenshi stepper (4.2V, 3.5A)
> >
> >
> >
> > - 5 AMP fast blow fuse
> >
> > - 470 uF (100V) (A Axis)
> >
> > - Gecko G201 (set at 2 A parallel or 1 A series)
> >
> > Vexta Stepping motor (3A, 1oHm, documents show 4.2V)
> >
> >
> >
> > Every Gecko will get its own set of wires to and from the large
> > capacitor, arranged in a "star" power distribution.
> >
> >
> >
> > Questions that I have:
> >
> > 1.) Any reasons why I should not be operate the drivers at the
low
> end
> > or high end, 24VDC and 80VDC? Will life of the drives and/or
> motors be
> > killed? Will they not spin as fast if the voltage is lower on
the
> end?
> >
> >
> >
> > 2.) Will this 4700 uF capacitor be able to help smooth out any
> problems
> > while the drives decelerate? Should I get a bigger one? If my
> 4700 uF
> > capacitor is not big enough, I have another 4700 uF capacitor --
> could I
> > connect them in parallel to get approx. 9400 uF, instead of
buying a
> > bigger capacitor if the need comes up? Are there any issues with
> this
> > parallel capacitor setup?
> >
> >
> >
> > 3.) On some people's setup, there is a 1.2K 5Watt bleed resistor
on
> the
> > large cap, do I need that? What does it do? Do I need a Zener
> diode,
> > or is it a good idea to use one anyways?
> >
> >
> >
> > 4.) Since I have 4 axis (sometimes which only two are being used
[x
> and
> > y]) will this effect any power issues? If all 4 axes are funning
> at the
> > same time, will this be too much of a drain on the system? If I
> only
> > use 2 of the axis in this 4 axis setup, will there be issues?
And
> how
> > can I resolve them?
> >
> >
> >
> > 5.) When looking for a transformer, is there anything I should
look
> for?
> > Are there any specific ratings I need for my setup? I have a
> 120VAC ->
> > 24VAC transformer, that's rated for 1amp, is this too weak?
Should
> I go
> > out and buy another 120->24VAC transformer that is also 1amp, and
> hook
> > them up in parallel? Can I even do this with AC power? Should I
> go out
> > and buy another transformer, if so at what sizes?
> >
> >
> >
> > 6.) Do I have my gecko G201 Amp settings correct for the drives?
> Or is
> > the AMP setting on the drive determined by means other than 2/3
and
> 1/3
> > pending on parallel or series (respectively)?
> >
> >
> >
> > 7.) If I run a stepper motor in parallel winding, is that more
> power or
> > more RPM? I know series would be the other.
> >
> >
> >
> > [Non-text portions of this message have been removed]
>
>
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