Re: [CAD_CAM_EDM_DRO] Re: LARGE Gantry table: Geckos on large servos.

----- Original Message -----
From: "Mariss Freimanis" <mariss92705@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, March 11, 2004 3:50 PM
Subject: [CAD_CAM_EDM_DRO] Re: LARGE Gantry table: Geckos on large servos.


> Peter,
>
> Jon is right; it does work that way and nicely too. Here's the math:
>
> Motor: 5 mH, 2 Ohm, 80VDC rated (about a 500W output motor)
> Drive: 25 kHz switching frequency
>
> Ripple current (p-p) = V / 2*f*L = 80 / 2 * 25,000 * 0.005 = 0.32A
> RMS current (triangle waveform) = I (p-p)/4 = 0.08A
> I^2*R heating = 0.08^2 * 2 = 0.0128 Watts
>
> The motor will be stone-cold when stopped and unloaded.
>
> Mariss
>

Then I stand corrected. I had worked on chopper drives long ago and that
is the way that
I remembered them.

Pete.