Ion Boldea

Experimental investigation of rotor currents distribution in three phase induction motors with symmetrical squirrel cage at standstill

This paper simply investigates experimentally multiple “rotor” bar current waveforms at standstill, on a dedicated inside-out induction motor prototype as a basis to analyze the asymmetry of bar currents. A phasor calculus scheme based on primary MMF space harmonics is developed to explain this asymmetry of bar currents at standstill for a symmetrical cage. The results of the paper should be a strong experimental foundation to investigate thoroughly the effects of rotor speed and loading and of broken bars on additional losses, torque pulsations, noise and vibrations in high performance induction machines.

Linear Electric Machines, Drives, and MAGLEVs: An Overview

Linear motion is rather common in the industry, and linear electric motors (LEMs) can provide it directly (without a mechanical transmission) through electromagnetic field forces. LEMs may be considered counterparts of rotary electric machines, but specific topologies lead to characteristics that differ (in some cases notably) from those of the latter. This paper attempts an overview on recent progress of LEMs, from innovative topologies to advanced modeling, design, and control, with case studies and examples related to specific industrial applications from people movers to small compressors solenoids, speakers, and microphones.

Experimental Investigation of Rotor Currents Distribution in the Healthy and Faulty Cage of Induction Motors at Standstill

This paper simply investigates experimentally multiple “rotor” bar current waveforms at standstill, on a dedicated inverted induction motor prototype as a basis to analyze the bar currents distribution in the symmetrical and unsymmetrical cage. A phasor calculus scheme based on primary magneto-motive-force space harmonics is developed to explain this asymmetry of bar currents system at standstill even for a symmetrical cage. The results of the paper should be a strong experimental foundation to investigate thoroughly the effects of rotor speed and loading and of broken bars on additional losses, torque pulsations, noise, and vibrations in high performance induction machines.

Reluctance Electric Machines : Design and Control

KEY FEATURES • Presents basic and up-to-date knowledge about the topologies, modeling, performance, design, and control of reluctance synchronous machines. • Includes information on recently introduced reluctance fluxmodulation electric machines (switchedflux, flux-reversal, Vernier, transverse flux, claw pole, magnetic-geared dual-rotor, brushless doubly fed, etc.). • Features numerous examples and case studies throughout. • Includes a comprehensive overview of all reluctance electric machines.

A step capacitor controlled 1 phase a.c. autonomous PM generator, with experiments

This paper introduces a high performance (90% efficiency) 3kW, 3000/3600rpm, 50/60Hz 1 phase autonomous PM generator with (8+2)kg total weight and simplified control (switched capacitor) control for max ±7% voltage regulation from pure resistive to resistive inductive (0.8 power factor, lagging) loads. Topology, design principles, FEM based characterization are accomplished by modeling for steady state and controlled transients. Finally full size experiments are used to validate the proposed power device so useful in various standalone applications.

Fast computation of bar over-currents in the faulty cage of induction motors with experimental validation

The paper proposes a fast estimation method for the over-currents that occur in a broken bar cage induction motor. In essence, simple analytical expressions of over-currents in the two healthy bars adjacent to the broken bars, for a few typical situations, are derived. These calculations should be also instrumental in broken bars diagnosis. The calculated over-currents in case of broken bars have been validated experimentally on an inverted induction machine with stationary cage which allows bar conductivity interruption and direct measurement of multiple bar currents.

Closed slot induction machine inductances and rotor resistance characterization versus current and frequency via FEM

The paper presents the inductances and rotor resistance estimation - using FEM - for the closed slot induction machine. One presents the variations of inductances and rotor resistance as function on current and frequency for emphasizing their dependence upon the saturation level of the machine. So it is possible to estimate the machine parameters for a large area of the operating modes.

MAGNUS — An ultra-high specific torque PM axial flux type motor with flux focusing and modulation

Axial flux permanent magnet (AFPM) synchronous motors are attractive for low speed direct drive systems because of their high specific torque. The present paper proposes a novel axial flux machine topology, called MAGNUS, obtained by combining a yokeless central stator type NS arrangement with two external high polarity spoke-rotors, resulting in very high flux concentration. The stator, which includes main and auxiliary teeth for air-gap profiling has a small number of concentrated coils. Two stator configurations are discussed, the first, a yokeless construction with coils wound around the teeth, and the second with coils placed around the stator core in a Gramme ring arrangement. Feasible slot pole combinations are identified. High torque densities are achievable owing to torque magnification achieved by air-gap profiling as well as flux concentration. Initial analysis indicates that this machine presents higher torque than a YASA machine, which currently holds a record for torque density.

Large wind generators design, performance and control: An overview

Wind energy installed power worldwide reached 350.000 MW in 2015 with strong prospects to grow notably in the next 20 years. The cases of E.U. and of Denmark are illustrated. Electric generators and their power electronics control represent an important part of any wind energy conversion system, besides the turbine, tower and auxiliary electrical equipment. Large wind generator transmission stages designs, tailored to application, of various types with ever better performance up to 10 MW per unit are envisaged for the near future and are presented in this lecture. The same technology is shown to be applicable to other related industries such as pump storage and inertial storage needed to reconcile wind energy production variability with consumers. Typical and new control systems for large wind generators are reviewed also.

Small single-phase two pole Ferrite-PM-stator double-saliency motor: Optimal design and experimental characterization

Stator-PM small motors are currently proposed for residential, automotive, info gadget actuators to decrease PM temperature effects and keep high performance, for lower cost, by using Ferrite-PMs and (or) aluminum stator windings. Single-phase stator-PM small motors did not receive sufficient attention for powers below 100W in general. The present paper characterizes a single phase two-pole Ferrite-PM stator double saliency, flux reversal motor, in terms of optimal design and detailed experimental validation. Starting from a previous recent paper of same authors, this paper expands the subject and introduces various test results on a subsequently built prototype which lead to higher efficiency than a three phase brushless d.c. counterpart at partial load (50%).