The magnitude of the rotor magnetic flux linkage and its spatial orientation within a permanent magnet synchronous motor directly define the angular position of the rotor and are thus used in many sensorless applications as the governing variables. The rotor magnetic flux linkage in the stator reference frame is represented by two orthogonal sinusoids whose amplitudes and phases are determined by the integration of the orthogonal components of the corresponding voltage, which, due to DC offsets and initial conditions at transient states, result in an integrational drift. This paper proposes a solution to the problem of such integrational drift in the form of a compensation based only on orthogonal properties of waveforms in the stator reference frame. That makes it completely independent of electrical parameters of the motor. As a result, the proposed compensation of the integrational drift does not require any optimization by the user and it is functional from a standstill. The effectiveness of the proposed compensation is demonstrated analytically, by a simulation, and an experiment on a real motor by a simple observer for the sensorless field-oriented control based on the voltage model in the stator reference frame.

High-performance electrical drives, typically comprised of permanent magnet synchronous motors (PMSMs), generally require correct values of electrical parameters for the tuning of controllers. Those parameters are also required for the estimation of the electromagnetic torque together with the magnetic flux linkages in the direct torque control (DTC) as well as for observers of the angular position and speed of the rotor in sensorless applications of the field-oriented control (FOC). In this paper, nonlinearities imposed by the voltage source inverter (VSI) that prevent direct measurements of electrical parameters are circumvented by a method based on quotients of secants as approximations of gradients of reference voltages and measured currents. While each measurement is performed without a position sensor at a standstill, the rotor has to be able to move to align itself with a required angular position. The novelty of the proposed method is the use of currents generated by the VSI for the alignment and the locking of the rotor. The proposed method is presented analytically and its functionality demonstrated by experiments.

A sealless pump, also known as a wet rotor pump or a canned pump, requires a stationary sleeve in the air gap to protect the stator from a medium that flows around the rotor and the pump impeller. Since the sleeve is typically made from a non-magnetic electrically conductive material, the time-varying magnetic flux density in the air gap creates an eddy current loss in the sleeve. Precise assessment of this loss is crucial for the design of the pump. This paper presents a method for calculating the eddy current loss in such sleeves by using only a two-dimensional (2D) finite element method (FEM) solver. The basic idea is to use the similar structure of Ampère’s circuital law and Faraday’s law of induction to solve eddy current problems with a magnetostatic solver. The theoretical background behind the proposed method is explained and applied to the sleeve of a sealless pump. Finally, the results obtained by a 2D FEM approach are verified by three-dimensional FEM transient simulations.

Estimations of magnetic flux linkages, either between the stationary windings of the stator for the direct torque control (DTC), or between the stationary windings and the rotor for the sensorless field-oriented control (FOC), are based on integration of corresponding voltages. Integration of voltages with offsets that come from improperly calibrated measurements as well as from transient states generally produces unwanted drifts in the resulting magnetic flux linkages, which when used within any type of control of sensorless electrical drives results in instability. This paper addresses that problem and proposes a simple self-contained solution based on orthogonal properties of waveforms of input voltages and resulting magnetic flux linkages in the frame of reference fixed to the geometry of the stator. The proposed solution requires only two periodic orthogonal input waveforms with a distinct common fundamental harmonic, which as such is independent of the type and parameters of the used machine. The idea of the proposed solution is presented analytically, its stability is proven by means of the quadratic Lyapunov theory, and its functionality is demonstrated by standalone simulations and experiments within the sensorless FOC of a permanent magnet synchronous machine (PMSM).