Active cooling for on-machine device

In permanent magnet servo motors, each component has a certain temperature limit. For on-machine device with electronic components, like the high resolution optical encoder, the temperature limit is commonly less than 125°C. While for the motor body, the winding and the magnets usually have higher temperature limit. During continuous operation, the encoder temperature, rather than the winding or magnet temperature can limit the output torque density particularly for non-ventilated / IC410 configurations. The encoder temperature limitation results in a de-rating of the motor continuous output torque. This paper investigates the torque de-rating problem caused by the optical encoder temperature limit. Three dimensional (3D) finite element analysis (FEA) simulations with different cooling approaches are made and an active cooling solution using a thermoelectric cooler (TEC) is proposed to reduce the encoder temperature and improve the torque output. Several prototypes with different cooling strategies are tested and compared to verify the analysis. Both computer simulation and experimental results validate the working principle and the effectiveness of the proposed active cooling system.