Mechanical power measurements of an electric machine are very important to help understand what the motor is doing at any given time and operating point. Mechanical measurements help characterize the motor, build up models for the machine, ensure confidence in controllers, and understand the limits of the system. Measuring torque with high accuracy, bandwidth, and resolution is particularly important for designing a controller and implementing an electric motor solution. In electric machines, we often want to understand the efficiency and dynamics. Since torque is not a static value, it is preferred to have a highly accurate averaged measurement. This is comparable to using RMS values for electrical efficiency. The torque accuracy is of high importance since electric machines can operate in the high 90’s of efficiency percentage. If a machine has a 98% efficient measurement with a ±3% error, this means it could have an efficiency of 101%, which is impossible. Therefore, a highly accurate torque measurement is required. This is a relatively new issue since internal combustion engine efficiency is much lower.
Topics covered in this paper include:
- Instantaneous and Average Torque
- Dynamic Load Testing
- Torque Ripple
- Control Change
Find out more information about the measurement of instantaneous torque ripple, transient torque, and electric machine characteristics.