Design and evaluation of the power and data contactless transfer device

The transmission of electrical power and data through rotating interfaces in spacecraft equipment is a common requirement which is frequently mission-critical. The use of slip-ring and roll-ring type units, especially for high rotational rates, presents many drawbacks such as friction torque, electrical noise, high contact resistance, wear, debris and criticality concerning reliability and lifetime. These difficulties may be eliminated by means of a Contactless Transfer Device (CTD). The design, development and testing of such a device is described. This space-compatible Breadboard Model (BM) is capable of transferring over 250 W and 5 Mbps bi-directional digital data. The design accommodates a central axle or pole of up to 55 mm diameter, and may be used in an in-side-in or an in-side-out configuration A modulated subcarrier capacitive technique is used for the transfer of multiplexed data, and a rotating transformer for power-transfer. A modular approach allows the design to be tailored to the needs of specific users, and to allow the option of a fully redundant implementation. The paper presents and discusses the results of an extensive evaluation program which covered functional, electromagnetic compatibility, thermal, torque and vibration testing