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Archive for July 23rd, 2013

Vexta C6925-9212K Stepper Motors

A box of surplus Vexta NEMA 23 stepper motors arrived:

Vexta C6925-9212K stepper motors

Vexta C6925-9212K stepper motors

The data plate sayeth:

  • Model C6925-9212K
  • 2 phase
  • 1.8°/step
  • 2.3 V
  • 3 A

According to Dan, who happened into the deal, that Vexta model number applies to their custom motors, which accounts for the fact that there’s no further data available anywhere.

[Update: A National Instruments description of the motor wiring.]

Dividing 2.3 V by 3 A = 0.77 Ω windings. Multiplying 2.3 V by 2 A suggests a 7 W maximum dissipation.

Poking around with a meter identifies the windings:

  • Blue – White – Red
  • Green – Yellow – Black

Given those colors, the Y G B W R K color sequence on the connector doesn’t make any sense to me. Most likely, there’s a standard I’m unaware of.

The resistance from the center taps outward measures 1.0 Ω, which is close enough to 0.8 Ω for me. Measuring across the whole winding gives 1.8 Ω.

The inductance is 1.0 mH from the center tap and 4.0 mH across the whole winding. Remember that inductance varies as the square of the number of turns.

The time constant for a complete winding = 2.5 ms = 4 mH / 1.6 Ω.

That’s all I know…

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