Modifying a power supply's output

[Bloy2004]

I have a power supply that puts out 95.6VDC as pictured. I need to alter its output to 75VDC to enable the use of a Gecko 320 which has a max input of 80VDC.
What are the options that can be applied to this power supply to bring it to the required 75VDC?

Bloy

[ViperTX]

How many amps are you planning on drawing at 80VDC? So, the options are rewind the toroid, use a DC to DC converter, or use a simple voltage divider. By the way, where did you find that toroid and the design for that supply.

[arvidb]

Viper, I'm not so sure a voltage divider will work with the varied loads of a servo/stepper?

Another option is to use a linear series regulator to make a regulated supply. You will burn 20 W of power for each ampere you draw from the supply (for a 95-75=20 V voltage drop), so this might not work too well, though...

I think your best bet is to rewind the toroid.

Arvid

[bunalmis]

You can reduce the coils of secondary of transformer.

[Al_The_Man]

There is an earlier post on modifying the TXR , not by re-winding, but taking turns off, the previous post covers drilling out (carefully) the centre eboxy if necessary.
Toroids usually have the secondary as the last winding so it is relatively easy. They are usually wound at around 2 to 3 turns/volt square laminated TXR's are usually around 5 turns/volt.
Al

[Bloy2004]

Hi!
The amps will be no more than 20 as that is the max of the Gecko320...although I CAN supply more as the Gecko has a current limiter adjustment.
I got the toroid on ebay a while back. Its primary is 208 and the secondary is 110/1900VA, but I am putting in 120vac on the primary. The caps are just 22000 100v/150surge.
The rest is just a 1000v 35Amp full wave bridge that also came from ebay.

That core is really solid..I was hoping that I could go with a step down tranny but boy things are getting heavy.

[ViperTX]

So, you are only using one Gecko? You can't step down DC only AC. So, is the output voltage that you're measuring under some load, if not then you need to add something like a 10 amp or 20 amp load and measure the voltage.

[Bloy2004]

If I can, and I think it will do it, is to run three geckos with total amps approximating 20 under extreme forces....probably even not that...
I'm sure this supply will handle three Gecko320s and the two other smaller motors, but short of taking away windings, my knowledge here is very limited and was hoping for some way to alter the output...whether from the ac or the dc to bring it down to the Gecko's voltage limit. Otherwise I would find the resources to get a Rutex drive.
Thanks,
Bloy

[ViperTX]

Well, I just thought of something...what's the voltage rating of your motors. That is the voltage that you should input to the Gecko.

[ViperTX]

Well if you want to mess with the input side...isolation transformer and a variac....but you need to measure the output voltage with a load and also what is the voltage rating of the motors.

[Bloy2004]

I will get that information....right now my wife is summoning me for supper...

I'll be back

Bloy

[Bloy2004]

Originally Posted by ViperTX Well, I just thought of something...what's the voltage rating of your motors. That is the voltage that you should input to the Gecko.

The rating of the pictured motor is 60V/krpm..so it can take up to 180 volts.
but it will function just fine with 75VDC (or Gecko320's max 80VDC).
The other two motors will max at 60VDC, though they will work fine with 50VDC. I DO have a supply of 50VDC,25amps for the two smaller motors which will be the Y and Z axes. The pictured motor will drive the gantry itself.
Bloy