Gerhard,

On Wed, 16 Aug 2006 08:46:00 -0300, Gerhard Fiedler wrote:

>...
> What kind of electric motor doesn't lose torque with increasing speed?

A synchronous motor.

> Doesn't a typical electric motor have an almost linear drop of torque with
> increasing speed? Highest torque (stall torque) at (almost) 0 speed, 0
> torque at the shaft at max. speed (when all the power is used to overcome
> internal friction and other losses)?

I don't know what you mean by a typical motor (there are very many designs) but no, a synchronous motor has maximum torque at its design speed, 
and it falls off either side of that.  They may have zero torque at zero RPM - I remember an electric clock when I was young which would not 
self-start - you had to pull out and release a knob on the back, which gave it a kick and it would run from then on, but from a standing start it was 
stalled.

"Capacitor start" motors again have insufficient torque to start in their running configuration, and a capacitor is switched into circuit to change the 
characteristics until a certain speed is reached, and it's then switched out.

Cheers,


Howard Winter
St.Albans, England


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist