Abstract
The focus of this study lies on the investigation of the space vector modulation of a self-sensing three-phase radial active magnetic bearing. The determination of the rotor position information is performed by a current slope-based inductance measurement of the actuator coils. Therefore, a special pulse width modulation sequence is applied to the actuator coils by a conventional three-phase inverter. The choice of the modulation type is not unique and provides degrees of freedom for different modulation patterns, which are described in this work. For a self-sensing operation of the bearing, certain constraints of the space vector modulation must be considered. The approach of a variable space vector modulation is investigated to ensure sufficient dynamic in the current control as well as the suitability for a self-sensing operation with an accurate rotor position acquisition. Therefore, different space vector modulation strategies are considered in theory as well as proven in experiments on a radial magnetic bearing prototype. Finally, the performance of the self-sensing space vector modulation method is verified by an external position measurement system.
Highlights
Magnetic bearings are of great significance for the stabilization of levitating rotors
The rotor can be stabilized by electromagnets, which is stated as active magnetic bearing (AMB)
The measurements on the prototype demonstrated the characteristics of different space vector modulations concerning self-sensing and current dynamic
Summary
Magnetic bearings are of great significance for the stabilization of levitating rotors. The self-sensing position determination of this study is performed by a modulation-based current switching ripple evaluation of the actuator coils. INFORM (Indirect Flux Detection by Online Reactance Measurement) method is used to determine the rotor position. This method was originally designed for the rotor angle determination of a permanent magnet synchronous motor [10]. Concerning AMBs, the INFORM method is based on a current slope measurement, detecting the inductance change depending on the rotor’s eccentricity. The current controller stops in equidistant time steps and measurement pulses are applied to the coils This approach has the drawback of a limited bandwidth of the position measurement and an interruption of the current controller. 3-Active pattern [12], is the point of origin for the space vector modulation in this work
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