Stepper Formulas

Stepper Formulas

What Voltage should the power supply be?

To calculate the voltage needed empirically take a 24 VDC power supply

or any power supply that you have on hand that is above the minimum for

the drive and hook it to the heaviest loaded axis.

Run that axis and increase the speed until you find the fastest speed

that it will run without missing steps with the test voltage.

Using the following formula you can determine your voltage needed.

Speed you want ÷ (Speed you got * 0.9) * Test voltage used = Voltage needed

Example (300IPM ÷ (150IPM * 0.9) * 24VDC = 53.3VDC

Just make sure that the voltage is within the range of your stepper driver.

What Voltage is my Stepper?

Some steppers just have the resistance and current on the tag.

When I asked this question I had to do a slap on the forehead!

Using Ohm's Law R x I = E (Resistance x Current = Voltage)

Example 1.1 Ohms x 2.8 Amps = 3.08 Volts

Compute Maximum Voltage vs Inductance

To compute the maximum voltage that you should use

depending on the inductance of the motor use this formula.

Maximum Voltage = 1000 * SQRT(inductance)

Example a motor that is rated at 1.5mH inductance per phase.

1000 * SQRT(0.0015) = 38.73 Volts MAXIMUM.

Example a motor that is rated at 6mH per phase

1000 * SQRT(0.006) = 77 Volts MAXIMUM.

Example a motor that is rated 2.5mH

1000 * SQRT(0.0025) = 50VDC MAXIMUM.

NOTE: Not all motors are created equal.

If you use this formula and your motor seems to be excessively hot, turn down the voltage

until the temperature is acceptable. Stepper motors are designed to run hot, but there's no

need to stink up the place with fried insulation.

Many motors are rated to withstand an 80 C temperature rise.

For my own purposes, I limit the temperature rise to 60 C.