Comparative Evaluation of Voltage- and Current-Impressed Inductive Power Transfer to Multiple Stainless-Steel-Enclosed Moving Receivers

Linear actuators in high-purity environments require full stainless-steel (SS) encapsulation and, advantageously, contactless, i.e., inductive power transfer (IPT) to several moving sliders which carry the actuator motor drives and application-specific tools. To avoid high eddy current losses in the SS enclosures by avoiding perpendicular magnetic field components, each IPT receiver features a closed toroidal magnetic core (with the secondary-side winding) that is arranged coaxially around the common primary-side winding which extends along the full stroke of the linear actuator. The primary winding is supplied with a full-bridge inverter through a compensation network that either compensates the primary windings’ series inductance (voltage-impressed operation, V-I) or ensures a constant, load-independent amplitude of the primary current (current-impressed operation, C-I). Both operating modes support operation with multiple receivers but differ in terms of realization effort and efficiency characteristics in dependence of the load situation and/or the number of connected receivers. Therefore, after introducing the operating principles, this paper proposes a procedure to identify optimum V-I and C-I designs for given specifications, which then facilitates a comparative evaluation. All in all, an optimized C-I system achieves better efficiencies in the range of 98% at high load and with the maximum supported number of receivers actually used, but this comes at the price of a larger and more expensive compensation network. The modeling procedure is finally verified by equipping an industrial SS-enclosed linear actuator demonstrator with IPT to two moving receivers, each providing an output power of 100W at an output voltage of 72V.