This paper proposes a new method for fast radial vibration computation in switched reluctance motors. Only a piecewise first-order linear function is used to calculate the total peak acceleration, which is rather fast. The overall radial vibration is the superposition of natural oscillation of each mode. Before that, several critical parameters need to be calculated or measured in advance, including weight factor, natural frequency and damping ratio of each mode, in order to obtain the respective analytical expression of natural oscillation of each mode. First, the total peak acceleration concerning the multiple of current and its slope is derived analytically from the perspective of abrupt change of radial force. Then, a simple method for calculating weight factors is presented for the distribution of peak acceleration of each mode from the total peak acceleration. Natural frequencies are measured and compared by three methods, including finite-element analysis, hammer impulse test, and dc pulse excitation. The calculation of damping ratio is improved since the traditional damping ratio calculation method cannot be used in a multiple degree-of-freedom system. Finally, both simulation and experiments are conducted to verify the effectiveness and accuracy of the proposed method.

It is well-known that current and radial vibration harmonic may cause resonance and will thus cause severe vibration and acoustic noise in switched reluctance motor (SRM). However, not each order of harmonic will cause resonance. It has not been fully discussed which order of current and radial vibration harmonic is the most important. This papers gives an analytical method to derive the most important order of current and radial vibration, which lays significant foundation for resonance reduction method. Then influence of different switch angles on current and radial vibration is analytically derived and comprehensively discussed. Based on that, resonance can be reduced by optimal switch angle selection considering efficiency sacrifice. Both simulations and experiments on a three phase sample SRM have verified the correctness of the analytical method and effectiveness of the optimal switch angle selection method.

The accurate model of switched reluctance motor (SRM) is critical for performance prediction. However, due to the doubly salient structure, the flux linkage of SRM is a non‐linear function with phase current and rotor position, which makes the determination of the characteristic of SRM very difficult. In this study, indirect measurement method is used to obtain the sample data and least square support vector machine (LSSVM) is used for the prediction of flux linkage. First, the basic principles of indirect measurement and the exact methods of realisation are presented. Second, the errors in the indirect measurements are analysed and post‐processing is given to reduce them. Third, the entire static electromagnetic characteristics are obtained by the prediction of improved LSSVM. The results are compared with those of using artificial neural network and those of using less training data by LSSVM, which shows both strong learning ability and generalisation ability. Finally, a simulation model is built up using MATLAB/Simulink and the results are compared between simulation and measurement. The good agreement shows that the proposed model has good accuracy. In addition, the LSSVM does not need any prior knowledge which is much easier for modelling than the existing literatures.

Radial vibration and torque ripple are the most two important factors to acoustic noise, especially when resonance is excited. This study focuses on radial vibration, which is composed of vibration impulse and fundamental vibration. The respective influence of the two components to resonance noise is analysed. It is experimentally demonstrated that fundamental vibration is more significant to resonance noise compared with vibration impulse. Accordingly, based on the already proposed randomising turn‐on angle method, the reduction effect of the method is analysed in detail using different control parameters like different variation range of turn‐on angle and different overlapping. The resonance noise is substantially reduced, which verifies the effectiveness of the randomising turn‐on angle. In addition, it is found that the reduction effect is almost the same by different control parameters, which shows the flexibility of the method.

In this article, a triple current slope difference (CSD) threshold based low-speed sensorless scheme for low-cost SRM drives is proposed. First, slope based methods, including the CSD method, are proposed and the advantages in terms of anti-interference ability over traditional instantaneous value based methods have been clarified. Second, the traditional single/double threshold methods and corresponding outgoing/incoming phase injection types are introduced and comprehensively compared. The limitations of conventional methods while adopted in low-cost SRM drives are stated. Accordingly, to solve the problem that the current cannot be obtained during the demagnetization stage in the resistor-based current sampling scheme, the triple CSD threshold method is proposed, whose third threshold indicates the zero-current position. Third, a general threshold value determination method considering the three-phase unbalanced inductances is proposed, which only requires the unsaturated inductance versus rotor position characteristics that is very easy to be obtained. The proposed method only needs to store six threshold values in the microprocessor and needs no complex calculations and additional hardware, which can be realized in low-cost drive systems. Finally, the experiments of both the steady-state and starting transient-state under over-load conditions are implemented to verify the feasibility and accuracy of the proposed method.

In this article, a novel method for online self-commissioning of the unsaturated inductance characteristics is proposed, which is utilized for low-speed sensorless control in switched reluctance machines. First, a dual-phase current chopping method is proposed to tune the rotor to any desired position, which does not need any clamping devices or position sensors. Then, the unsaturated inductance values at some sample positions are identified by the well-known current slope difference (CSD) method. Afterward, a feature position identification method combined with a regional linear interpolation method is proposed to construct the accurate full-cycle unsaturated inductance. To this extent, the self-commissioning process finishes and the controller switches to normal sensorless control mode. High-frequency (HF) pulses are first injected into the idle phase and the discrete inductance value during each pulse is identified by CSD. Based on the self-commissioning of unsaturated inductance characteristics, the discrete rotor position corresponding to the discrete inductance value is calculated. Accordingly, the more precise real-time rotational speed and rotor position are calculated based on a phase-locked loop. Finally, the constructed unsaturated inductance and the sensorless control scheme are both verified by experiments, which demonstrates the effectiveness and accuracy of the proposed method.