Design of a Minimum Current Magnetic Bearing

Current consumption of active magnetic bearings is an essential factor for the runnin_ costs and particularly for the acquisition costs. The maximum value of the needed current defines the size of the power amplifier, the diameter of the windings and the size of the slots etc. For the same lifting capacity, size and costs can be reduced significantly by reduction of the current. This paper analyses the current consumption systematically. At first it shows how the bias current premagnetization can be replaced by permanent magnets. Different constructions are discussed. Furthermore, a control strategy will be presented, which minimizes the DC currents necessary for the support of static loads. The avoidance of currents caused by imbalance compensation has already been discussed in former papers. All three measures together are usable to reduce the current consumption of AMBs significantly. Solely the transient currents are still required.