Re: Stepper Drivers

stratton@... wrote:

> From: stratton@...
>
> > Oh, now we're really going off the deep end. We were talking about
> a
> > suitable transformer for some 24 W stepper motors. Yes, if you use
> a
> > 5 KVA transformer, you will have no trouble providing 75 Watts to 3
> > motors, and you will also prevent thieves, tornados and tsunamis
> from
> > stealing/blowing/washing away your CNC control!
> >
>
> I'm not sure they are 24 watt motors. They may be rated to dissipate
> 24 watts as heat, but how much electrical energy can they convert to
> mechanical energy? I suspect more than that.

Well, if a standard stepper driver is used, with some method to limit
current (ie.
resistors or chopper drive) then the motor power dissipation at idle is
provably
more than the maximum mechanical power output of the motor.
Actually, a motor with extremely small inductance and a very carefully
designed
chopper drive might be able achieve more power out than the idling
power,
but it could be quite tricky to obtain. Most steppers have very large
inductance, which affects performance even at very low speeds.

The only way to get more power out, is to have some mechanism to raise
motor
current with increasing speed. There have been some systems that do
things
like this, but they are not used, to my knowledge, on the small, home
shop
CNC setups.

Jon