Re: [CAD_CAM_EDM_DRO] Re: Confused over My own Calculations!

On Sunday 18 August 2002 01:59 pm, Jon wrote:

>
> Now, this is ONLY at idle, and will vary due to the design of the motors
> and drivers. When the motor is producing substantial torque at some
> speed, the power drawn will increase dramatically, and therefore the
> current mist also rise. But, the peak power may occur only during
> acceleration, and therefore be transient. So, you should not need a power
> supply rated for continuous output of 8 A per motor in the above example.
> Probably 4 A/motor would work in most cases, except where you know all
> motors would be accelerating simultaneously.
>
> Jon
>

Jon, or anyone else

This is just to satisfy my curiosity as I'm running servos and really don't
ever plan on using steppers again. The servo performance is so much better.

Anyway, we always talk about raising the voltage on a stepper system to
overcome the inductance in a stepper motor's windings. It would seem that at
a high step rate the voltage will not be building up to the max that the
power supply can deliver, and since the resistance of the windings will not
change, why wouldn't the current be more when the motor was not turning.
At idle the voltage will have had plenty of time to raise to the max level
and and hence, using ohms law the full current that can be delivered by the
drive should be flowing. But at speed the voltage will be lower and it seems
as though the current should also be lower. What am I missing here

I know a few years back while running a stepper system with a chopper drive
the motors would get hot as hell while standing still but cool down
considerably when running. Obviously there was no current reduction on that
drive.

Just curious
Bill