Re: max voltage for Electrocraft servo

Hello,
I have two types of bigger Electrocraft servos. Models E643 and
E712. They are both rated at 60V. That doesn't mean that your
smaller motors will run 60V, however, but it just might be.

I believe you can calculate max voltage by knowing MAX RPM and KE.
For example one of my servos has a max RPM of 4800 and a KE of
~12.5v/1000 RPM. 4800/1000 = 4.8, 4.8 * 12.5 = 60V. Maybe this is
just a coincidence, but it seems to work.

From what I've learned from Mariss himself, supplying 70V to a 60V
servo isn't by itself a problem, as the servo drive only puts out
what is needed to maintain servo lock. The problem is when YOU
command the servo to go faster than it's supposed to and having the
extra voltage to drive the servo to it's death. Keeping your PS
within 5V of the motors voltage is simply a safety. With load, and
other losses, you will run out of power before you can overdrive your
servos.

I'm not recommending that you run 70V to your servos. I'm just
telling you what I've picked up. Be aware, unlike steppers which
simply loose steps and shed extra energy, servos will gladly burn
themselves down if they are powered and commanded beyond mechanical
and thermal means. Get in touch with Mariss if you can, he would be
the best one to listen to.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "grantfair2001"
<grant.fair@s...> wrote:

> I have some used Electrocraft E543 brush servos. I did track some
> specs on them, but there was nothing on max. motor voltage.
>
> Does anyone know what this is? Or is there a way to determine this
> from the other specs (KT, KE, max continuous current, motor terminal
> resistance at 4 amps, etc.)?
>
> I know someone who is running these at 67 volts without any

problems.

> But I am cautious (as all this servo stuff is new to me) and the
> Geckodrive 320 (which I haven't tried yet becuase of this question)
> information states not to exceed the motor's rated voltage by 5

volts.

>
> Grant