What phase inductivity value should my stepper motor have?

Stepper motor phase inductivity varies widely. Even for a given size of stepper motor, such as NEMA17 with a length of 38mm, you can buy widely varying inductivity values even from the same manufacturer:

• NEMA17x38 from Nanotec with 25mH inductivity
• NEMA17x38 from Nanotec with 8mH inductivity

Both of these have the same holding torque of 80Ncm. Inductivity is not an indicator of motor power! As a general rule, remember:

• NEMA17 steppers tend to be in the 1mH to 50mH range.
• NEMA23 steppers tend to be in the 250μH to 25mH range

If you are checking your motor for a shorted winding, if the inductance is below 100**μ**H, you can be pretty sure that the stepper motor is defective.