Re: Power Supply and Capacitor Questions Help!! sizing

I did the calc's on the caps, and with a 31 VAC transformer rectified
to 43.8 volts, and a 13.7 amp load, you need a 25kuF capacitor.

IF (big if) you can get the 31V and 10V out of the transformer for 41
volts, your 57.9VDC voltage would reguire an 18,905 capacitor.

lower voltage would use a higher capacitor, and there is no reduction
in voltage on my calc's for the voltage drop of the rectifier, but it
should be in the 1.2 volts range.

The next calculation would be for the size of the filter capacitor.
Use the equation of (C= (80,000 * I) / V)). C is the value in
microfarads, I is the current and V is the voltage.


It seems like two caps in parallel (NOT SERIES) will offer 30,000uF
so should work.

Visit the www.geckodrives.com page for the calculation listed above
and a paper on power supplies.

About bleed resistors, why ? the drivers will blead the caps in
short order and all you are doing is adding a mini low watt heater.




Dave




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

> Hello,
>
> I'm in the process of assembling a CNC control consisting of

the

> following: 4 axies, 3-40 in/lb DC brush type servo motors that are
> rated 40v/K at 2500 rpm 13.7 amps maximum current. 1 servo motor

for

> the 4th axis which I have not obtained yet but will be smaller. I'm
> using Mach2 for a control program. Bob Campbell's Sound Logic
> breakout board for Mach2. I'm using Gecko 320 drives. 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.