A reliable switching amplifier for active magnetic bearings

In this paper a concept for a reliable switching amplifier for active magnetic bearings is presented. Depending on the reliability required, it consists of two or more left and right switching amplifier half-bridges. These so called "hot swap modules" (HSMs) are connected in parallel, each with its own error detection and decoupling circuitry. If an error occurs in an HSM, it is autonomously switched off and disconnects itself from the AMB-actuator, while the remaining, fully functioning HSMs take over the required current. The faulty HSM can be replaced by a functioning one during full operation of the AMB in a hot-swap procedure. For recognition of HSM-errors the functions of several components on each HSM are monitored, for example IGBT and diodes of the half-bridge and the correct operation of the error detection circuitry. To test the basic functionality of this concept along with the behaviour during component-faults extensive simulations with PSpice were carried out. Simulation results allow an efficient and reliable design of the error detection circuitry.