Permanent Magnet DC Motor

This model is based on a Faulhaber Series 0615 DC-Micromotor. For the 1.5V variant, equivalent circuit parameters are given as:

Rotor resistance R=3.9 Ohms
Rotor inductance L=12uH
Back emf constant K=0.072mV/rpm
Rotor inertia J=0.01gcm^2
Friction torque Mr=0.02mNm

The model uses these parameters to verify manufacturer-quoted no-load speed, no-load current, and stall torque, which are:

No-load speed = 19,100rpm
No-load current = 0.03A
Stall torque = 0.24mNm

When running the simulation, for the first 0.1 seconds the motor has no external load, and the speed builds up to the no-load value. Then at 0.1 seconds the stall torque is applied as a load to the motor shaft. Zooming in on the RPM and Motor Current scopes shows a good level of agreement with manufacturer data.

Often manufacturers do not quote the equivalent circuit parameters, and they must be estimated from information such as no-load speed, stall torque, and efficiency. A test harness such as this model can then be used to test the estimated equivalent circuit prior to using the motor model in a complete system simulation.