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Selecting Brushless DC Motors for Initial Testing in Cardiovascular Applications

February 8, 2024

When an engineer begins the development of a new cardiovascular device, motor selection is a critical component to achieving the desired performance requirements. Brushless DC motors are the ideal technology for these devices, but the challenge lies in identifying the micro-motor that is most suitable for initial testing. In this article, we'll dive into the key considerations that should govern this selection process.

1. Mechanical Envelope. The cardiovascular device features a basic envelope that includes set dimensions for the motor. The motor's diameter and length are critical factors that influence its performance capabilities, with both dimensions needing to be evaluated in conjunction with the overall device profile. The reason is simple – equivalent performance may be achieved by opting for a larger diameter and shorter length motor, or conversely, a smaller diameter and longer length motor.

2. Working Point. The power requirement is defined by the calculations completed for the device performance, which will determine the speed and torque output needed from the motor. Engineers can identify the precise working point by examining the speed/torque curves for each motor, ensuring that it falls within the continuous or intermittent range relevant to the application. This approach guarantees that the motor's performance aligns with the specific demands of the device.

3. Thermal Considerations. The motor constant, defined by R/K2 (resistance divided by the torque constant squared), is the merit factor to use to ensure the temperature rise will be optimal during operation. This must be closely evaluated to ensure that the selected motor can sustain optimal thermal conditions during prolonged usage.

4. Duty Cycle. The application will determine the on and off time for the motor during operation.  For continuous operation, it’s recommended that the motor torque, current, and maximum speed not be exceeded. For initial testing, it is best to ensure a safety factor for the torque and current due to additional friction that may be present in the early prototypes of the device.

By addressing each of the above factors, engineers can lay a solid foundation for the cardiovascular device's micro-motion system, ensuring optimal performance and reliability as the development progresses. Portescap’s engineers have extensive experience in this design process, including readily available specification pages that provide the technical details (including the speed/torque curves), as well as an eStore for purchasing motor prototypes online. Reach out to us here to start collaboration on your next device iteration!