Search

A numerical prediction of electromagnetic interference (EMI) allows evaluation of EMI performances at the design stage and before prototyping. It can also help reduce the post-prototype electromagnetic compatibility cost by minimizing late redesign and modifications of a drive implementation. This paper describes two simulation approaches with time- and frequency-domain simulations and verifies them with experimental results. Both time- and frequency-domain simulation approaches are found effective as long as the noise source and propagation path are properly modeled. The three-dimensional (3-D) finite-element-analysis (FEA)-based parasitic parameter extraction tool--Ansoft Spicelink has been used substantially. To gain additional degree of confidence, the results obtained from FEA are verified with closed-form solutions and actual measurements. Index Terms--Electromagnetic interference (EMI) modeling and simulation, inverter EMI.

The paper presents methodologies to detect and locate short-circuit faults on the stator winding of VSI-fed PM brushless dc motors. Normal performance characteristics of the motor are obtained through a discrete-time lumped-parameter network model. The model is modified to accommodate shortcircuit faults in order to simulate faulty operation. Fauit signatures are extracted from the waveforms of electromagnetic torque and phase-voltage summation using wavelet transform. Three independent detection techniques are introduced. Experimental measurements agree acceptably with simulation results, and validate the proposed methods. This work sets forth the fundamentals of an automatic fault detector and iocator, which can be used in a fault-tolerant drive. Index Terms--Brushless dc motor, fault detection, wavelet transform.

The paper presents a neuro-fuzzy-based perspective to the automation of diagnosis and location of stator-winding interturn short circuits in CSI-fed brushless dc motors. Performance of the drive under normal and short-circuit conditions are obtained through classical lumped-parameter network models. Waveforms of the electromagnetic torque and summation of phase voltages are monitored to develop two independent diagnostic algorithms. Diagnostic indices derived from the characteristic waveforms using discrete Fourier transform (DFT) lead to identifying the number of shorted turns. Fault location is achieved through a different set of indices extracted by the short-time Fourier transform (STFT). Adaptive neuro-fuzzy inference systems (ANFIS) are trained based on simulation results to automate the diagnostic process. ANFIS testing along with the good agreement between simulated and measured waveforms show the effectiveness of the proposed techniques. Index Terms--Brushless dc motors, fault diagnosis, fault location, inter-turns, neuro-fuzzy systems.

In this paper, a 12-V 1-kW permanent-magnet ac motor drive is tested extensively at a wide frequency range, and the frequency spectra are partitioned for identification of noise sources and their propagation paths. Switching characterization of the power MOSFET and its body diode reverse-recovery characterization are evaluated for circuit modeling. The parasitic components and common mode path are identified and measured with the time-domain reflectometry (TDR) method. The inverter circuit model is then constructed with major parasitic inductance and capacitance in device modules, passive components, leads, and interconnects. To verify the validity of the inverter model, a comparative study is performed with computer simulations and hardware experiments. The fundamental mechanisms by which the electromagnetic interference (EMI) noises are excited and propagated are analyzed, and the significant roles of parasitic elements coupling with device switching dynamics in EMI generation are examined. The results indicate that the identification of parasitic inductance through TDR measurement helps verify the voltage spike during turn-off, or vice versa. The conducted EMI noise caused by parasitic components of bus capacitor, dc bus, and devices is proven to be identifiable with the characterization and simulation techniques used in this paper. Index Terms--Electromagnetic interference (EMI) simulation, parasitic models.

An analytical approach is developed to predict the inverter high frequency pulse width modulation (PWM) switching caused eddy-current losses in a permanent magnet brushless dc motor. The model uses polar coordinates to take curvature effects into account, and is also capable of including the space harmonic effect of the stator magnetic field and the stator lamination effect on the losses. The model was applied to an existing motor design and was verified with the finite element method. Good agreement was achieved between the two approaches. Hence, the model is expected to be very helpful in predicting PWM switching losses in permanent magnet machine design. Index Terms - Eddy-current loss, permanent magnet brushless dc motors, pulse width modulation switching, space harmonics.

This paper examines the possibility of using permanent magnets (PM's) in the design of solid-rotor eddy-current couplers and brakes. The analysis is based on a magnetostatic finite-element model modified to include an eddy-current distribution calculated in solid parts through an iterative process. Various rotor constructions, with a single layer of either iron, aluminum, or copper or with a composite layer of iron/aluminum or iron/copper, are investigated. The latter offers markedly superior performance, which should, in most cases, justify the extra construction complexity. Magnet construction, in particular the number of poles, is also investigated. The torque characteristic and the design of couplers using PM's seem to differ from their electromagnet-based counterparts, and the paper compares and contrasts the two, in order to identify the applicability of each. The model results compare satisfactorily with the test results obtained from a prototype device. Index Terms - Couplers, eddy currents, electric machines, permanent magnets, retarders.

Semiactive suspension systems using real-time damping (RTD) provide significant improvement in vehicle ride and handling without the high cost of fully active suspensions. RTD systems require a variable rate damper (shock absorber), a relative velocity sensor (RVS), and a controller. To reduce the cost of such systems, a method for integrating a moving magnet relative velocity sensor directly into the shock absorber is presented. This integrated relative velocity sensor (IRVS) uses existing hydraulic and mechanical components as part of its magnetic circuit to reduce part count and cost. Sensitivity to key design parameters is analyzed using a finite element model. The IRVS is self-energizing, requires no signal processing electronics, and can be integrated into standard shock absorber configurations. Prototype sensors were tested on a vehicle and provided excellent performance under all testing conditions.

A two-dimensional finite element model is developed to model the electromagneti behavior of permanent magnet type eddy current couplers under constant speed operation. The model accounts for the nonlinearity of the steel flux paths and is verified using test measurements from a prototype eddy current coupler. The proposed solution differs from conventional magnetostatic finite element models in that an unknown current-density distribution must be determined through an iterative process. The model is used to study the influence of certain design parameters on the torque-speed characteristics of such devices.