Electric Motor Dynamometer

The torque-speed relationship is a key indicator of electric motor performance as the shape of the characteristic curve changes as the motor’s health deteriorates. The relationship can be modelled as a function of the motor torque constant, the motor e.m.f constant and the resistance.

This project designed and fabricated a testing rig for micro DC electric motors with a torque lower than 0.4 Nm. A stepper motor on the rig applies loads to the motor. The loads are measured by a strain gauge. A Labview program stores data from a tachometer mounted on the test motor and the strain gauge to determine the torque-speed curve.

A brushed micro DC motor was used to test the rig’s design and capability. The rig was calibrated over 14 hours of testing to determine relationships between the torque, speed, current, voltage and the strain gauge reading. Analysis of data gathered indicated the stall torque of the test motor to within 4% of the rated torque of the motor. The total cost of the testing rig including fabrication was $1730.

The testing rig provides the basis for future testing of a range of micro motors. They will be tested over long intervals under different conditions and loads. The decline in performance will be monitored and quantified.  The data will be used to determine relationships between motor performance and condition variables such as temperature, vibration, current and voltage. This relationship informs the development of prognostic models.

Leave a Reply