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Posted by dan michaels on April 11, 2006, 6:13 pm
guesswhat@gmail.com wrote:
> Hello,
> I have a stepper motor with 48Vdc and 3 Amp. I would like to design
> a non linear dc power supply to powe this stepper. Could somebody point
> it to me how can I size the capacitor on the dc power supply? I am
> planning to use a regular transfomer to conver regular 208Vac to 48Vdc.
> For the calculation, the RMS value on the transformer's secondary
> side is 34Vdc (48Vdc/1.41) and the voltage across the load capacitor is
> 68Vdc. My question is that how do I size the proper capacitor to power
> my stepper motor?
You should be able to find info on power supply design on the web.
Offhand, I'd say you're in trouble on this, and you might be better off
springing $100 or so to buy a regulated supply off the shelf.
Roughly speaking, you want to keep the ripple down to 1%, which is
probably still high, and you'll need roughly 50,000 uF.
At 68v, your 48v stepper will pull something like (68/48) * 3A = 4.2
Amp. If you use full-wave rectification, then the half period is about
0.008 sec. For a 1% drop, the dv will be about linear, so you can
estimate the capacitance from I = C dv/dt, or C = I * dt/dv, giving
C = 4.2A * 0.008 sec / (0.01 * 68V) = 49,000 uF
First guess.
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> I have a stepper motor with 48Vdc and 3 Amp. I would like to design
> a non linear dc power supply to powe this stepper. Could somebody point
> it to me how can I size the capacitor on the dc power supply? I am
> planning to use a regular transfomer to conver regular 208Vac to 48Vdc.
> For the calculation, the RMS value on the transformer's secondary
> side is 34Vdc (48Vdc/1.41) and the voltage across the load capacitor is
> 68Vdc. My question is that how do I size the proper capacitor to power
> my stepper motor?