Re: Power Supply and Capacitor Questions Help!!

--- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers <rogersmach@y...>
wrote:

Ron,

I am using similar size motors for XY&Z and a smaller motor for A. I
am using the same 3 caps. As this is my third iteration of this
supply, having upgraded motors, I used the following mounting
layout: The 3 capacitors, bridge rectifier and individual fuse
holders are mounted on one side of 1/2 al. plate, the 4 Geckos are
mounted on the other side of the plate. The capacitors are connected
by copper buss bars, I used flattened 3/8" copper tube. Power wiring
to the Geckos is from the nearest point on the buss bars to the
drive, the positive via a fuse. As the longest lead is less than 6"
there is no need for the ESR cap directly across the Gecko power
inputs. Using this configuration I found that the radiated switching
spikes are almost completely confined and and the drives are much
more predictable.

As added precautions I also use a NTC inrush surge suppressor (to
prevent trips on power up), and added Mariss's circuit shown in the
files section as "Power Supply.pdf", this protects against damage
from back voltages generated by the motors.

In another post you queried the use of gas struts; have you, or are
you, replacing the knee screw? If you haven't then there is
considerable ineffiency in ACME screws and you will probably not be
able to gear the servo sufficiently to get into its power band.
There have been several posts on this subject and also on the use of
counter balances in the past.

On the question of the transformer temperature, at this stage I
suggest suck it and see, also you will benefit by adding cabinet fan
(s). If you need a more definitive answer there is someone on the
list (Jan Rowland?) who has details of power transformer sizing.

Hope this helps,

Bernard

> Hi Bernard,
> Thank you for taking the time to respond. I did what you

suggested and put the 33 v tap and the 12v together in parallel and
it works. I misread those the other day. Anyways I'm getting about 47
volts out of my supply. Jon Elson mentioned on another email that
these two sets of taps may not be isolated from one another. Its
working so I'm assuming they are. I left my Transformer plugged in
for about 2 hours with no load and one lead from each set still
connected and it got rather warm, still touchable but warm. is this
normal? Also, do I need all these Capacitors?(they consume 1/4th of
my cabinet) Ive got 3 at 100 vdc and 15,000 macrafarads each. On
another Email someone mentioned that two at this value should be
sufficient. And the bleed resistors are getting omitted due to the
responses ive recieved. Everyone is saying I dont need them because
Gecko has them built in.

>
>
> Ron
> Bernard R <bwjarandall@c...> wrote:
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "rogersmach"
>
> Wire the capacitors in parallel, you only need 1 resistor if you

feel

> you need a bleed. Check the wire size of the transformer
> secondaries, if they are similar, wire the 31 V in series with the

10

> V, check with a voltmeter you should get 41 VAC, if its 21V swap

one

> pair of windings. Use one bridge rectifier across the 41VAC, when
> connected with the capacitors you will get (41 x 1.414) - approx

1.5

> (bridge diode drop) VDC, near enough 55 VDC, you can increase it to
> slightly over 60VDC by also including the 4 volt tap, again if it

is

> of similar gage ( or bigger) than the other two. The 320s are
> conservatively rated at 80VDC.
>
> Bernard
>
> > Hello,
> >
> I'm using a
> > power supply from the old control of my bridgeport which has 4

set

> of
> > output taps on the secondary and their voltage values are: 1 set

at

> > 31 volts AC, 1 set at 10 volts AC, 1 set at 4 volts AC and the
> other
> > set read 0. In talking with Mariss at Gecko drive (brilliant man,
> > hate to bother him), he suggested that I use about 60 volts DC

with

> > his drives. Which would reduce the speed with little effect on

the

> > torque (if I understood him correctly). And I would need a 100

volt

> > DC capacitor rated at 45,000 macrofarad or greater. I could not
> > locate a cap with this value and had to settle for 3 100 volt
> > computer grade DC caps at 15,000 macrofarad. Question: Can I wire
> > these 3 capacitors in series to achieve the same Macrofarad

value?

> I
> > intend on using a 1.2k 5 watt bleed resistor on each. Next
> Question:
> > Would it be possible for me to run the 31 volt taps through one
> > bridge rectifier and 10 volts through another bridge rectifier,
> wire
> > them in parallel to get my output up to around 41 volts DC? Is it
> > possible to change the configuration of the primary side and get
> > higher values? I intend to use the present supply temporarliy to
> get
> > operational, then acquire a more adequate supply later. At the 31
> > volts it appears to be pushing the X axis (servo running directly
> off
> > of bridge at 31 volts DC without capacitor and a 2.5:1 reduction)
> > about 30 inches/min Id like to get it around 70 or 80 inches /min
> > rapid. Any more than that is unsafe on a bridgeport. Any input on
> my
> > inquiries would be appreciated.
>
>
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