blazini36 wrote: I'm trying to figure out a good capacitor value for the 8i20 with the 750w BLDC. I'll be running it off of straight rectified 120v AC so it's 160v DC. I have a bunch of 470uf caps I can run in parallel, a 1000uf cap or a 4700uf cap. I'd prefer to use a single 1000uf or the 4700uf because they have screw terminal and mounting options
You can find online calculators to help with this:
www.changpuak.ch/electronics/power_supply_design.php
(For direct-on-mains connection I think you just need to set the delta-volts-per-amp to 0. Load resistance can be got from R = V^2 / P )
Bear in mind that the servo won't be working at full power for very much of the time, so you should consider when doing the calcs.
One critical thing is the ripple current, and the ripple current rating of the capacitors. If your cap is something like this:
uk.rs-online.com/web/p/aluminium-capacitors/3819245/
Then it is rated 15A ripple current, which looks about OK given some allowance for the servo duty cycle.
It is interesting to note that the ripple current is higher with a bigger cap, partly because the average load voltage is so much higher.
On balance, I think I would use the 4700uF one.
