A simple dynamic model of a controlled DC motor consisting of a variable voltage source, a couple of resistors, an inductor, and an electro-motoric force element representing the coupling between electric energy and mechanical energy provided by the magnetic field in the DC motor. The motor axis is represented by a rotating inertia. Reliability annotations have been added to various components in the model.

Comparison of step response for the rotational speed of the inertia using the default parameters (DCMotor 1) and with resistances in resistor1 and resistor2 set to 20 Ohm, inductance 0.1 H, and moment of inertia to 0.3 kg m²  (DCMotor 2):