Martian Mot

Effects of stator slot magnetic wedges on the induction motor performances

The paper presents some aspects of magnetic wedges application in electrical machines. The slot opening distorts the waveform of the air-gap flux density and produces high order space harmonics, which causes increased additional losses and torque ripples and reduces both the power factor and efficiency of the machines. FEM-analysis is used in order to investigate some effects of stator slot magnetic wedges on an induction motor performances. The test results and FEM-simulations are very close and prove that the utilization of magnetic wedges is a good solution to improve the performances of the induction motor with open stator slots.

Testing of electrical machines in periodical and quasi-periodical conditions, using a data acquisition and processing system

The paper presents the procedures and the results of electrical machine testing accomplished by these authors using a specialized data acquisition and processing system (DAPS), they designed and built. This DAPS is aimed to measure and monitor electrical machines while operating in transient or steady state regimes. The architecture of the DAPS and the functionality of its components are described in the first part of the paper. To emphasize the versatility of the DAPS, some examples of testing electrical machines for periodic and dumped periodic regimes are given. The hardware programmability of the DAPS signal adapter and the modularity of the related software can extend the DAPS applicability to testing any electric high power equipment.

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.

Low speed PM generator for direct-drive wind applications

The paper deals with the design, FEM analysis, and testing of a surface-mounting permanent magnet (PM) generator with an inner rotor for wind applications. The purpose of this work has been to build a PM generator with simple structure, good performances and very low cogging torque. The paper presents the main design aspects and the performance characteristics of a 5 kW, 120 rpm and some test results of the PM generator prototype. Good agreement between simulated and experimental results has been achieved.

Low speed synchronous generator with PM excitation

The paper deals with the design and testing of a surface-mounting permanent magnet (PM) generator with an outer rotor for variable speed applications. The purpose of this work has been to build a PM generator with simple structure, good performances and relatively low costs. The paper presents the main design specifications and the performance characteristics of a 3 kW, 250 rpm and some test results of the PM generator prototype.

Computer Aided Testing of Electrical Machines

The paper presents a computer controlled platform that authors devised and built for testing electrical machines both in laboratory and in industrial environments. The hardware and software architecture of the system were developed to address the testing specifications required by standards or requested by customers. Also, the results of several significant measurements that were performed with this automatic test-bench are presented. The testing platform was employed for testing electrical machines in various settings like mixed-frequency alternate current regime, amplitude modulated quasi-periodic regime, aperiodic transitory regime, to name just the most relevant ones. Prototype tests were carried out over medium power induction motors and synchronous machines, and the results of these measurements are presented here.

Experimental model of a hydrogenerator with static excitation

In this paper is presented an experimental model for an hydro aggregate with synchronous generator having static excitation. The model was designed and achieved in the laboratory at reduced scale, of 12 kVA, using a VI — LabVIEW environment. With the help of this model there might be experimentally studied the dynamic conditions of the real hydro generators in function.

Analytical estimation of the Roebel bar losses

The paper presents an analytical method for the Roebel bar losses computation. The most general Roebel bar structure, including both solid and hollow elementary conductors was considered. Using the proposed method it was developed a computing program which estimates with a good accuracy the bar losses. One can analyze the influence of any input quantities (machine and material data) on the bar losses. So it is possible to optimize the Roebel bar structure for the machine efficiency improvement.

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.

Performances analysis of an induction motor with stator slot magnetic wedges

The medium and high power induction machines are usually built with prefabricated insulated coils. In these cases, by technological reason, the stator is designed with rectangular shape open slots. Because of the large width of the open slot, the air-gap magnetic field is distorted (comparatively with the situation of other types of slots shape), having high order space harmonics with significant amplitudes. Consequently, the pulsating torque components, noises and vibrations appear, and both the power factor and the efficiency decreases. To avoid these unfavorable effects of the open slots, the magnetic wedges are used. In this work, some aspects concerning the influence of the magnetic wedges on the performances of induction motor with open slots are analyzed. In this purpose the finite element method (FEM) and tests are used. It comes out that between the experimental results and FEM simulation results is a good concordance. This analysis confirms that the use of magnetic wedges in the case of an induction motors with open slots is a suitable solution to improve the electrical machines performances.