Everyone needs a variable power supply for bench testing of your motors right? Well, a lot of the motors out there seem to run on 12 & 24V, which is no problem, but what about the ones that take 90V? Must you make/buy a separate power supply for each one?
My goal right now is to run some 24V brushed DC motors (Yaskawa Minertia R-series servo motors). The data sheet (for the 50 oz-in one) specs the stall current at ~28 amps IIRC, which would dictate my overall power rating I would think. However, if some higher voltage (i.e 90 V) DC motors come along at a later date, it would nice to be able to run them off this same supply as well.
I've considered going the PWM route, with 90VDC as the rail voltage, but have concerns about such a large square wave pulse if used with lower voltage motors, even if the duty cycle provided the appropriate "RMS" voltage. And if I used a 24 V rail voltage, then it wouldn't be capable of driving a 90 V DC motor I wouldn't think.
I was thinking of making a linear power supply to have the capability of running any range of voltages between ~0 and 90+volts DC. Anybody do this before? The vast majority of one's I've seen out there go ~1.2-36 VDC (probably for good reason, I'm just not experienced enough know why)
After trying to find some multi-tapped transformers that would provide the appropriate levels of AC, I started thinking about using a variac to supply 0-120 VAC, followed by a diode bridge rectifier of appropriate maximum rating, and some fairly large filter caps dictated by my max voltage (rectified 120VAC). This would provide an unregulated source of DC. I haven't thought through how to regulate anything above 36V yet, but.....
I was considering using an LM317 voltage regulator (~1.2V - 36V IIRC) that would be switched into the circuit for cases where I was needing voltages below 36V, to provide much better regulation without a lot of fuss. I haven't checked the current capacity of the LM317 yet, so it may not be up to the task. Perhaps if I lower the current requirement to ~3-5 amps @ 24V (since I won't be using this to power the system, just want to bench test the RPM/volt spec on the encoders, probably under minimal load), this would become more practical?
I haven't thought through cases higher than 36V yet -- would the unregulated supply have a LOT of voltage droop under load at, say, 90V?
Again, I haven't considered all the details of this design yet, I was just wondering if you folks tend to draw a line between 0-24 VDC and the "higher-voltage" motors and get different power supplies for these two cases.
Chad