bridge rectifier

[osdhillon]

Hi everybody

I need help in selecting the right bridge rectifier and other components to drive my three 170VDC servo motors @ 9 amps each.

I was thinking to use 5KVA transformer which will give 120vAC at the secondary coil. I need to convert this 120vAC to 170vDC. What kind of bridge rectifier I should be looking for. Then I need to select the right transformer to store 170vDC (@ 27 amps). Your help is appreciated.

Thanks
Onkar singh

[Al_The_Man]

Bridge rectifiers do not go up that much in price for the larger values so go with something like a GBPC3504W 400V at 35 amps.
For the transformers look up Hammond, for a 240/120 or 120/120, I would think you could go with a 4 kva at 60% duty cycle as you are probabally not going to see maximum power on all three motors for any extended time.
You will also need a electrolytic capacitor bank for 5% ripple at that voltage/current around 10,000µfd.
Some amplifier manufacturers recommend grounding the motor negative, if you do, do not ground the secondary of the transformer.
Al.

[osdhillon]

Al
Regarding the capacitor. Do i need 170v 10,000 ufd? Where can I find it? Any suggestions.
Thanks
Onkar singh

[Al_The_Man]

Go with 250~200vdc minimum, they are not cheap at that voltage, Electrosonic in Canada is one source, You may have to parallel a couple of 5,400µfd. Or ebay may be another alternative.
Al.

[Russ Shugg]

Hello, The rutex website, (rutex.com) has a paper that you can download regarding power supply/servo motor matching that will point you in the right direction for proper sizing of transformer etc. I purchased the bridge rectifiers for my power supply on EBAY for $9.00 each (40 amp @ 500 volt) and actually I have a few left if you need one or can't find them on ebay. I got my capacitors from a fellow CNC builder, so I cant help you there. 5 kva sound a bit big because I doubt you will be running all (3) axis full tilt for extended moves at the same time. Good Luck!!