Three-Axis Inductive Displacement Sensor Using Phase-Sensitive Digital Signal Processing for Industrial Magnetic Bearing Applications

Teemu Sillanpää,Jouni Vuojolainen,Pekko Jaatinen,Alexander Smirnov,Olli Pyrhönen,Rafal Jastrzebski,Niko Nevaranta

doi:10.3390/act10060115

Teemu Sillanpää, Jouni Vuojolainen + Show 5 more

Open Access

https://doi.org/10.3390/act10060115

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Journal: Actuators	Publication Date: May 31, 2021
Citations: 9	License type: CC BY 4.0

Affiliation: Lappeenranta-Lahti University of Technology

Abstract

Non-contact rotor position sensors are an essential part of control systems in magnetically suspended high-speed drives. In typical active magnetic bearing (AMB) levitated high-speed machine applications, the displacement of the rotor in the mechanical air gap is measured with commercially available eddy current-based displacement sensors. The aim of this paper is to propose a robust and compact three-dimensional position sensor that can measure the rotor displacement of an AMB system in both the radial and axial directions. The paper presents a sensor design utilizing only a single unified sensor stator and a single shared rotor mounted target piece surface to achieve the measurement of all three measurement axes. The sensor uses an inductive measuring principle to sense the air gap between the sensor stator and rotor piece, which makes it robust to surface variations of the sensing target. Combined with the sensor design, a state of the art fully digital signal processing chain utilizing synchronous in-phase and quadrature demodulation is presented. The feasibility of the proposed sensor design is verified in a closed-loop control application utilizing a 350-kW, 15,000-r/min high-speed industrial induction machine with magnetic bearing suspension. The inductive sensor provides an alternative solution to commercial eddy current displacement sensors. It meets the application requirements and has a robust construction utilizing conventional electrical steel lamination stacks and copper winding.

Highlights

IntroductionMany industrial processes are based on pumping or compressing liquids or gases
Many industrial processes are based on pumping or compressing liquids or gases.Such processes include, for example waste-water purification plants based on aeration compression, heating, ventilation, air conditioning and refrigeration (HVACR) systems based on liquid chiller compression and sub-sea gas compression units helping to utilize the full potential of subsea gas fields
In typical active magnetic bearing (AMB) levitated high-speed machine applications, the displacement of the rotor in the mechanical air gap is measured with commercially available eddy current-based displacement sensors

Summary

Introduction

Many industrial processes are based on pumping or compressing liquids or gases. Such processes include, for example waste-water purification plants based on aeration compression, heating, ventilation, air conditioning and refrigeration (HVACR) systems based on liquid chiller compression and sub-sea gas compression units helping to utilize the full potential of subsea gas fields. A common factor for these processes is that the actuator, for example, a compressor, pump or blower, benefits from the use of very high rotational speeds of up to several hundred thousand rotations per minute. The low-efficiency gearbox between the electrical machine and actuator can be removed by integrating the frequency converter driven high-speed electrical machine with the magnetic bearing suspension on the same shaft as the actuator. The result is increased overall efficiency, higher power density and smaller size [2]

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