Re: [CAD_CAM_EDM_DRO] Cheap Servo Motor?

Mariss Freimanis wrote:

>Hi,
>
>I stumbled across this motor:
>
>http://www.surpluscenter.com/item.asp?UID=2003070308293941&item=10-
>1931&catname=electric
>
>It's rated at 4800 RPM at 120VDC with a continuous rated torque of
>250 in-oz.
>
>Working the numbers gives a Kv of 25 volts / 1,000 RPM and a Kt of
>33.8 in-oz per Amp.
>
>At 72 volts you would get 2,880 RPM and draw 7.4 Amps at its rated
>torque. The power output would be 533 Watts or about .71 HP. I don't
>have this motor nor have I tested it with our G320 drive but it may
>work.
>
>At $24.99 it may be worth a gamble.
>
>

That is a VERY good deal, if it will perform adequately as a servo motor.
C&H and others would sell a motor like this for a lot more. One nice
thing to know would be the armature resistance. That is the big problem
with
the Ametek motors that so many people use. The 4.x Ohm resistance combined
with wire and transistor drop means you can't even get full torque with a
72 V supply.

And, of course, if it has bad torque or velocity ripple, it won't be as
good for
smooth low-speed movement.

Jon