Practical Method for Experimental Detection of DC Motor Inertia to Design a Speed Regulator

The paper presents a practical step by step tutorial how to determine the moment of inertia and mechanical losses in DC electrical machine and use this information to design speed and current regulators. The experimental procedure for detecting moment of inertia is described in the paper. During this test the motor is accelerated above its rated speed, what can be easily done by using field weakening and then disconnecting motor from the power supply. The speed change during the time are measured and then by using mathematical expressions the moment of inertia could be found if the power losses are known. The paper provides experimental verification of separation of mechanical losses from the total armature losses. In the paper accurate and approximated mathematical models of DC motor in frequency domain are shown. Bode plot method is applied to analyze stability of speed and current regulators. The controller is implemented in digitally controlled DC-DC converter and experimental results are shown.