Centroid Community CNC Support Forum

BartakamosRex wrote: ↑Thu Feb 18, 2021 5:22 pm I thought of that, but I didn’t want to buy an expensive transformer to find that it wasn’t supplying enough voltage. I wasn’t sure what the calculation is to figure that out— is it just as simple as applying the percentage?

cncot wrote: ↑Thu Feb 18, 2021 7:29 pm I just built and tested an exact replica of the capboard connected without a transformer today.
I found with 180 ohm load the voltage drops to 145 VDC RMS. I have not yet, but I believe if I put my Oscilloscope on it I would find that the tops of the ripple are being knocked off....
If you want more measurements, write back, I am retrofitting an anilam 1100, but nothing is wired yet. The anilam motors are 140 volt. I reused the old components except for changing the capacitor to a 120,000 microfarad capacitor and an adding an Antihrium 25 amp inrush limiter in between the bridge and the capacitor.. These motors ran for over 30 years on this supply. If you carefully limit the maximum allowed speed in the setup of the allinone, you should never reach 150 volts. I don't know the exact voltage/speed ratio of your motors, but if you start at a very slow speed limit and measure the voltage while running at the limit, then repeat while slowly upping the limit, you will find a happy sweet spot compromise. Don't set faster than the slowest speed you can live with, keeping in mind that you want to keep your voltage under an arbitrary safe upper limit. Give yourself some room for transients, etc. according to the slowest fast speed you can live with. Why not post your measurements? Let us know how it turned out..

tblough wrote: ↑Thu Feb 18, 2021 8:07 pm

BartakamosRex wrote: ↑Thu Feb 18, 2021 5:22 pm I thought of that, but I didn’t want to buy an expensive transformer to find that it wasn’t supplying enough voltage. I wasn’t sure what the calculation is to figure that out— is it just as simple as applying the percentage?

Yup. Transformers are all about the turns ratio. There are some small losses in transformers, but essentially the turns ratio = the voltage ratio, the VA is the same in both sides, and it doesn't matter which is primary and which is secondary.