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Stepper Vs Servo Motor Torque Curves Part III

NEMA23 Single Stack Motors

In this post, I’m going to look at some fun NEMA23 single stack servo motors and a single stack stepper motor.  The entrants are:

  • In brown, the PacSci M21 with Sigmax technology.  The M21 has a lot more torque than many (most?) NEMA23 single stack steppers.
  • In blue and red, one of my favorite motors: the BH02300 servo motor.  I’ve spun one of mine at 20,000 RPM.  Like the Emoteq QB series, the BH series has great peak torque.
  • In yellow and green, the MCG (now Ametek) I2351014NC servo motor.  After all the high end motors, I decided it was time to feature a non-exotic and affordable (if you can get it) motor.


  1. The difference between the I2351014NC and the BH02300 is the peak torque (the BH02300 has much more) and maximum speed (20,000 RPM vs 12,000) and, of course, price; continuous torque is about the same.
  2. Both servos are can go much, much faster than the M21 stepper (although at 3000RPM, it’s pretty fast for a stepper motor).
  3. The M21’s continuous torque looks pretty good; it always has more continuous torque than either servo, and below about 2000 RPM has more continuous torque than the I2351014NC has peak torque.
  4. OK, it’s not really far to compare these motors — they obviously have their own areas (low end torque and low cost for the M21, high speed and moderate cost for the I2351014NC, and high speed, high peak torque, and high cost for the BH02300) but it’s fun to see big differences between motors that are all about the same size.



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