RE: [CAD_CAM_EDM_DRO] Re: Here's my proposed power supply setup.

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@...]
Sent: August 16, 2002 4:13 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
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]


Addresses:
FAQ: http://www.ktmarketing.com/faq.html
FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/

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