Re: [CAD_CAM_EDM_DRO] Re: capacitor

I just do a quick rough calculation where the total energy of
a regenerative brake at max velocity (1/2mv^2) plus
the energy stored in the motor field (1/2Li^2) equals the additional energy
in the supply cap (1/2C(v+vr)^2 to find
the voltage rise in that cap. I needed about 20,000 uf
to keep the rise a few volts maximum without using a
shunt regulator.

Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.rabun.net/~leswatts/wattsfurniturewp.html
engineering page:
http://www.rabun.net/~leswatts/shop.html

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, March 20, 2002 12:38 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: capacitor


> mariss92705 wrote:
>
> > Jon,
> >
> > Good points except for the cap size which is a bit of an over-kill. I
> > suggest using the following for sizing caps:
> >
> > For 60Hz, C = (80,000 times I) / V
> > For 50Hz, C = (100,000 times I) / V
> >
> > Where V is the power supply voltage, I is the maximum power supply
> > current and the answer, C, is in microfarads.
> >
> > This scales the ripple voltage to about 10% of the output voltage and
> > keeps the power factor reasonable.
> >
> > For 10A @ 80VDC, this yeilds 10,000 uF at 60Hz.
>
> Well, maybe I'm thinking of Servo power supplies, but I use a MUCH bigger
> cap than that in my power supply. But, then, a servo can really draw
> substantial current surges. Also, unless you have a braking resistor
> and control circuitry, you need enough energy storage to prevent the
> DC bus from surging during motor deceleration.
>
> Jon
>
>