Problem in Stepper Motor block Parameters with predefined parametrization

I am using the stepper motor block provided in the Simscape toolbox R2020b. I used the predefined parametrization from the provided motors list. The selected motor was Minebea 17PA-KA39B, as seen in the below picture.

From the manufacturer catalog, the motor data are shown in picture 1. The most important are the rated current, 1A, and the holding torque: 610 mN.m. Also, the supply voltage for this motor is 24 V, as seen in picture 2.

The Torque constant is not provided in the motor data, but Matlab provided a value of 606 mN.m/A, as seen in picture 3. It seems this value is calculated as Holding Torque / Rated current = 610 mN.m /1 A, which is about 606 mN.m/A.

I have run a Matlab model with a stepper motor block with Minebea 17PA-KA39B data, and the supply voltage is 24V. The phases currents and Torque are shown in picture 4, and here the differences appear as follows:

1- The Max phase current is 4A, which is 4 times the rated current provided by the manufacturer (1A).

2- The holding torque is 2.424 N.m, which is 4 times the holding torque provided by the manufacturer (606 mN.m).

What is the reason behind these differences?

Answer 1

[Vishwa]

Stepper motor has some unique characteristics. It is a dynamic motor, characteristics depends on the:

1. Load inertia, it will decides the maximum step rate
2. Load damping and load torque
3. Motor drive (voltage-controlled, current-controlled)
4. Speed-torque curve provides information, for a particular step rate, what is the maximum load torque it can acheive without slipping. Datasheet gives the data for constant current-controlled drive for micro-stepping. If you provide current controlled drive like input current of 1 A, you will get the rated torque.
5. Voltage-controlled and current-controlled drive operation offer different performance for stepper motor.
6. Stepper motor performance is very limited with constant voltage drive.

Kindly refer these example to understand how to generate these curves.

1. Pre-Parameterized Stepper Motor Block Validation: https://de.mathworks.com/help/sps/ug/pre-parameterized-stepper-motor-block-validation.html
2. For approximate parameterization refer this example: https://in.mathworks.com/help/sps/ug/stepper-motor-pull-in-characteristics.html

Hope that helps!