[tesart]

I am retrofitting a compumill 4000. I plan to install Gecko drives and Mach3. The Geckos are limited to 80VDC. The transformer in the machine puts out 63VAC from 220 which when rectified gives me about 86VDC. What can I do to lower the dc a bit?

Thanks

Tom

[irving2008]

I am retrofitting a compumill 4000. I plan to install Gecko drives and Mach3. The Geckos are limited to 80VDC. The transformer in the machine puts out 63VAC from 220 which when rectified gives me about 86VDC. What can I do to lower the dc a bit?

Thanks

Tom

Tom, you need to be looking at 65v DC to allow for Back-EMF from the drivers. This means you need
to drop the AC from the transformer to 45v,AC which is quite a large drop. Is unlikely you can do anything on the DC side because of the current draw.

You have these options:

1/ replace it with a 45v AC transformer

2/ use an external autotransformer to reduce the input volts from 220 to 157v

If its a toroidal transformer you have two other options...

3/ remove some of the secondary winding - this is quite easy to do unless its overwound paralleled secondaries (because then you have to fully unwind the top one to unwind part of the bottom one, then rewind the top one again)

4/ create a 'buck' winding on the transformer. Find some wire similar to what its already wound with. Wind 10 turns onto the transformer and measure the volts across the ends (V). Unwind then wind ((63 - 45) * 10/V = 180/V turns on. Connect this new winding in series with the original secondary so as to reduce the voltage there (you will need to experiment which way round, one way will increase the volts, the other way will reduce them). If there are two paralleled secondaries you will need a buck winding for each. If there are two in series then only one winding needed.

Persoanlly I'd go with option 1 as the quickest/easiest but maybe not the cheapest...

[tesart]

Thanks you. I'll look at the options, I may be farther ahead to get bigger drivers.

Tom