Accurate heat loss evaluation of water-cooled electric motors using a differential ultrasonic calorimeter

Measuring thermal losses of electric motors is important for their design, optimization, and correct pricing after manufacture. This measurement can be conducted by checking the temperature difference of the motor coolant (usually water) between the coolant inlet and outlet. High speed measurement facilitates testing various load scenarios and manufacture throughput; high measurement accuracy and resolution is required for drawing the correct conclusions on the efficiency of design alterations. Ultrasonic temperature sensors can quickly sense temperature with high resolution and accuracy across the entire ultrasonic pathway. However, conventional high resolution ultrasonic sensors are expensive. By contrast, oscillating ultrasonic temperature sensors can be implemented using mass produced transducers and electronic parts at a fraction of the price of conventional high resolution ultrasonic measurement equipment. The presented ongoing research focuses on the development of a differential ultrasonic oscillating temperature sensor for evaluation of power losses in electric motors. Computer simulations, electronic and firmware design, and experimental results are presented and discussed.