Abstract: A self-adjusting magnetic bearing automatically adjusts the parameters of an axially unstable magnetic bearing such that its force balance is maintained near the point of metastable equilibrium. Complete stabilization can be obtained with the application of weak restoring forces either from a mechanical bearing (running at near-zero load, thus with reduced wear) or from the action of residual eddy currents in a snubber bearing. In one embodiment, a torque is generated by the approach of a slotted pole to a conducting plate. The torque actuates an assembly which varies the position of a magnetic shunt to change the force exerted by the bearing. Another embodiment achieves axial stabilization by sensing vertical displacements in a suspended bearing element, and using this information in an electrical servo system.

Abstract: A DC-DC current-mode controlled flyback switching power supply provides a high efficiency of operation throughout a wide range of input voltages. An error amplifier produces an error signal from the difference between a reference voltage and an output voltage feedback signal. The error signal controls a VCO that sets a latch to enable a power switch to store power in a flyback transformer. A comparator compares the error signal against a current sense feedback signal indicating the current flowing through the power switch. The comparator resets the latch and disables the power switch to transfer the stored energy in the flyback transformer to the output of the power supply. The extended input range of operation is achieved by varying the switching frequency of the DC-DC converter through the use of the VCO to accommodate varying input voltages and loading.

Abstract: In a safety system for a stepper-motor drive, a stepper motor for operating a throttle valve has poles with windings. Each pole winding is divided into part-windings, each of which is driven by a dedicated output stage. As a result, in the event of a failure of a part-winding or an output stage, it remains possible to control the stepper motor.

Abstract: Apparatus and method are disclosed for use with a starting circuit to prevent start-up of an electric motor when the motor's insulation resistance is of a value below a selected insulation resistance limit value below which the motor should not be energized. The selected limit value is a selected percentage of a known maximum value. A variable resistance device, such as a potentiometer, having first and second adjustable resistance portions is adjusted so that the adjusted resistance value of the second portion is of the same percentage of the total resistance value of the first and second portions as the selected percentage discussed above. A DC test voltage of a known value is applied to the motor's insulation resistance to cause a test current to flow therethrough. The test current is directed to flow through the second resistance portion to develop a test voltage.