Active magnetic bearing controller

Abstract

Unique systems, methods, techniques and apparatuses of active magnetic bearing control systems are disclosed. One exemplary embodiment is a power converter electrically coupled to an active magnetic bearing (AMB) having a plurality of windings, the power converter comprising a DC bus, two capacitors, a first leg, a second leg, and a controller. The capacitors are electrically coupled in series between the positive rail and negative rail, one capacitor being electrically coupled to the other capacitor at a midpoint connection. The first leg comprises a first semiconductor switching device and a first output node. The second leg comprises a second semiconductor switching device and a second output node. The first output node is electrically coupled to the midpoint connection by way of a first AMB winding and the second output node is electrically coupled to the midpoint connection by way of a second AMB winding.

1 . A power converter electrically coupled to an active magnetic bearing (AMB) having a plurality of windings, the power converter comprising:
 a DC bus having a positive rail and a negative rail;   two capacitors electrically coupled in series between the positive rail and negative rail, one capacitor being electrically coupled to the other capacitor at a midpoint connection;   a first leg electrically coupled between the positive rail and the negative rail, the first leg comprising a first semiconductor switching device electrically connected between the positive rail and a first output node;   a second leg electrically coupled between the positive rail and the negative rail, the second leg comprising a second semiconductor switching device electrically connected between the negative rail and a second output node; and   a switch controller electrically coupled to the first semiconductor switching device and the second semiconductor switching device,   wherein, the first output node is electrically coupled to the midpoint connection by way of a first AMB winding, and   wherein, the second output node is electrically coupled to the midpoint connection by way of a second AMB winding.   
     
     
         2 . The converter of  claim 1  additionally comprising a pair of current sensors, one sensor being electrically coupled between the first output node and the midpoint connection by way of a first AMB winding and the second sensor being electrically coupled between the second output node and the midpoint connection by way of a second AMB winding. 
     
     
         3 . The converter of  claim 2 , wherein the sensors are shunt resistors structured to take a series of current measurements and transmit the measurements to the switch controller. 
     
     
         4 . The converter of  claim 1 , additionally comprising a third semiconductor device in communication with the switch controller, the device being electrically coupled between the positive rail and the negative rail; and a diode electrically coupled to the positive rail between the third semiconductor device and the pair of capacitors, wherein the switch controller is structured to open and close the third semiconductor device so as to perform power factor correction. 
     
     
         5 . The converter of  claim 1 , wherein the switch controller is structured to control the first semiconductor switching device and second semiconductor switching device so as to provide power to the first and second AMB winding. 
     
     
         6 . The converter of  claim 5 , wherein the switching controller is structured to provide power to the first AMB winding with the first semiconductor switching device and to provide power to the second AMB winding with the second semiconductor switching device such that the power provided to the first AMB winding and second AMB winding is substantially cophasal. 
     
     
         7 . The converter of  claim 1 , additionally comprising four pairs of legs electrically coupled between the positive and negative rail, each leg having a semiconductor switching device and an output node, wherein a unique AMB winding is electrically coupled between each output node and the midpoint connection. 
     
     
         8 .- 14 . (canceled) 
     
     
         15 . A method for providing power to a plurality active magnetic bearing (AMB) windings with a power converter, comprising:
 coupling two capacitors in series across a DC bus, the capacitors being electrically coupled at a midpoint connection;   coupling a magnetic driver circuit to the DC bus, the magnetic driver circuit having a first leg with a first switching device and a first output node, and a second leg having a second switching device and an second output node,   coupling at least one of the AMB windings in series between the midpoint connection and the first output node;   coupling at least one unique AMB winding in series between the midpoint connection and the first output node; and   providing power to the AMB windings by operating the first switching device and second switching device.   
     
     
         16 . The method of  claim 15  wherein the power provided to the AMB windings is provided in a substantially cophasal manner by simultaneously providing power to the first output node and second output node. 
     
     
         17 . The method of  claim 16  wherein power provided to the first output node has voltage substantially opposite to the power provided to the power provided to the second output node. 
     
     
         18 . The method of  claim 15  additionally comprising balancing the voltages across the capacitors. 
     
     
         19 . The method of  claim 18 , wherein the voltage across the capacitors is balanced by:
 coupling the first output node and the midpoint connection in series by way of an inductor;   coupling the second output node to the first output node; and   operating the first switching device and second switching device such that the voltage across each capacitor is substantially equal.   
     
     
         20 . The method of  claim 19 , additionally comprising sensing current flowing through each AMB windings using a shunt resistor.