Re: Choosing Power/Volts on Stepper Motor

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Luke1027 <luke1027@p...> wrote:

> How do you choose the right supply voltage to run my Stepper Motors at?

Voltage and Current are seperate.

Voltage should be at least 5 times the nameplate and no more than 25
times nameplate.

Current is at nameplate, depending on the drivers. some drivers use
nameplate current for each phase, so double nameplate per motor.
others, specifically choppers use the wattage of the motor so you can
calculate backwards.

Assuming the driver you want to use is rated for 30 volts, you are
good as far as the voltage/motor is concerned.

The amps would be best determined by the board manufacturer.

it may be that the chips are the A3977 chips from Allegro.

That being the case, it is a chopper and you can use 1.5 amps per
motor and not 1.5 amps per phase. (3 amps for the motor)

> If I figure how much power I need by multiply the IPM by in-oz (motor
> Specs) and then dividing the result by 531. My results will be in Watts
> of power. So how do I take this result in Watts and figure out what
> voltage I should be running my Stepper Motors at?

The motor will be run at 2.3 volts and 1.5 amps no matter what power
supply voltage or current you have. That is if the driver is set
correctly.

What the higher voltage does is to inject a very fast current into the
motor to get it to move quickly. Then chop the power to maintain the
nameplate rating for the motor.

The calculations for motor electrical watts is not the same as
calculating delivered power watts. It would be great if it were that
simple. But I have a 150 oz-in motor that is rated almost identially
in current as a 810 oz-in motor and almost half the volts.

1.7 volts 4.7 amps = 150 oz-in 7.99 watts of electrical power
4.7 volts and 4.7 amps = 810 oz-in, 22 watts or slightly under 3 times
the electrical power, but 5.4 times the mechanical power.

Those are old motors, check the new hybreds, Camtroncis has 1,303
oz-in steppers with 2.5 amps. I am pretty sure they are not 85 volt
motors, so they are getting a considderable difference in delivered
power than electrical power.

Work out your mechanical watts and compare that to the motor rating in
delivered mechanical power.

Mariss has mentioned motor power in relation to the voltage, but I do
not recall a simple calculation that would align the two.

Dave

>
>
> Motor Example:
>
> 4 Wire Bipolar Stepper
> 2.3 Volt/Phase
> 80 oz.-in.
> 1.5 Amp/Phase DC,
> 1.5 Ohm/Phase,
> Steps 200,
> Size NEMA 23
>
> Motors to be used on Table Top CNC with 200 IPM max.
>
> The reason I ask is I want to decide which driver to go with to run 3
> axis. One axis needs to have two motors used it.
>
>
> Luke