Re: Stepper Voltage, does it really matter?

Michael,

It matters a lot if you need more than just holding torque. The rated
voltage on the motor simply means if you apply that DC voltage to the
motor, it will draw the rated current.

The faster a step motor turns, the more it resists current. It
requires a higher voltage to overcome this resistance. This voltage
must be current limited when the motor is stopped, otherwise the
motor will over-current.

As a rule of thumb, the maximum power supply voltage should be no
more than 20 times the motor's rated voltage. This means 36VDC for
your 1.8V motors and 120VDC for your 6V motors.

You can limit current with resistors or make a circuit that limits
current by pulse-width modulating (PWM) the motor. Using resistors is
very simple but inefficient; they generate a lot of heat, 300W
potentially for your 4.8A motor. PWM drives are very efficient but
complex.

Mariss

--- In CAD_CAM_EDM_DRO@y..., "Michael Holm" <Michael@H...> wrote:
> I'm building my first cnc mill, and have been picking steppers up
from here and there. I now have around 12 steppers, of which 4 looks
pretty good. (Large, cool looking, 200steps/rev) :o)
>
> When I connect my psu from my childhood race-track (6V, 10VA) they
all deliver a very good holding torque, while not running warm, so I
think they'll all run resonably with that psu.
>
> The thing is... On the two largest steppers are a small sticker
that says "VOLT DC 1.8 AMP DC 4.8A/PH" and one of the smaller
says "1A/PH" no voltage on that one., and the last says "6.0V/PH,
1.2A/PH" How do I decide what powersupply to use?
>
> I also have a 300VA 12V PSU and a 150VA 12V psu. What combination
will give me the best performance, and do I need to limit the current?
>
> What else should I look out for?
>
> Thanks.
>
> Michael
>
>
>
>
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