PWM Supply Research Articles

Diagnostic information contained in inter-harmonics of a direct and PWM supplied induction machine

The paper contains waveforms of currents for the direct and voltage source inverter supplied induction machine, with account for harmonics and inter-harmonics. By direct supply the grid is assumed to be polluted by 3rd, 5th and 7th harmonics, normally present in real power supply systems. The voltage inverter was assumed to operate in a PWM mode, with perfectly constant DC link current. Spectrums of stator currents for direct supply create reference bases for spectrums by PWM supply. The model of the machine accounts for dependencies of stator and rotor inductances on rotor angle, resulting from winding and air gap geometry. Calculations of the derivatives of inductances, with respect to rotor angle, allowed for calculation of electromagnetic torque and machine's dynamics, with allowance for speed fluctuation, also in steady state operation.

Design advantages and analysis of a novel five-phase doubly-fed induction generator

PurposeThe purpose of this paper is to provide an analysis of the performance of a new five-phase doubly fed induction generator (DFIG).Design/methodology/approachThis paper presents the results of a research work related to five-phase DFIG framing, including the development of an analytical model, FEM analysis as well as the results of laboratory tests of the prototype. The proposed behavioral level analytical model is based on the winding function approach. The developed DFIG model was used at the design stage to simulate the generator’s no-load and load state. Then, the results of the FEM analysis were shown and compared with the results of laboratory tests of selected DFIG operating states.FindingsThe paper provides the results of analytical and FEM simulation and measurement tests of the new five-phase dual-feed induction generator. The use of the MATLAB Simscape modeling language allows for easy and quick implementation of the model. Design assumptions and analytical model-based analysis have been verified using FEM analysis and measurements performed on the prototype. The results of the presented research validate the design process as well as show the five-phase winding design advantage over the three-phase solution regarding the control winding power quality.Research limitations/implicationsThe main disadvantage of the winding function approach-based model development is the simplification regarding omitting the tangential airgap flux density component. However, this fault only applies to large airgap machines and is insignificant in induction machines. The results of the DFIG analyses were limited to the basic operating states of the generator, i.e. the no-load state, the inductive and resistive load.Practical implicationsThe novel DFIG with five phase rotor control winding can operate as a regular three-phase machine in an electric power generation system and allows for improved control winding power quality of the proposed electrical energy generation system. This increase in power quality is due to the rotor control windings inverter-based PWM supply voltage, which operates with a wider per-phase supply voltage range than a three-phase system. This phenomenon was quantified using control winding current harmonic analysis.Originality/valueThe paper provides the results of analytical and FEM simulation and measurement tests of the new five-phase dual-feed induction generator.

Particular Model for Efficient Switching Frequency Loss Consideration in Surface Mounted Permanent Magnets

The paper proposes a particular modeling procedure for efficient switching frequency loss consideration in surface mounted permanent magnet rotors in cases of PWM supply. The model is based on 2D finite element analysis combined with circuit equations in the permanent magnet regions enabling end effects consideration associated with the switching frequency, which is responsible for the major part of eddy current losses in the magnets. The model’s accuracy is validated through measurements in a magnetic circuit. Comparison between measured and simulation losses by implementing a traditional loss separation analysis has illustrated the relative dominance of switching frequency eddy current losses in permanent magnets and the feasibility of the proposed methodology.

Flux and Loss Map Based Evaluation of the Efficiency Map of Synchronous Machines

This article presents a methodology for the efficiency maps evaluation of synchronous electric machines. The procedure is based on the manipulation of flux linkage, iron and PM loss maps obtained via 2D magneto-static Finite-Element Analysis. The paper thoroughly describes the procedure and its key computational steps, all referring to open-source Matlab code available to the public. A method for iron loss evaluation from magneto-static FEA is proposed, valid for both sinusoidal and PWM supply. Experimental results are provided for the validation of single loss terms calculation and for the whole efficiency map, with reference to an interior permanent magnet machine designed for traction. FEA evaluation of PWM supply conditions relies on the off-line computation of the motor phase currents using a custom PLECS model of the drive, still flux-map based. This step of the procedure is also validated experimentally. The proposed methodology covers permanent magnet synchronous and synchronous reluctance machines, and finds prominent application in the automotive field, for traction and on-board generation.

Electric Bicycle with Fuzzy Logic Control

Abstract: This system monitors speed of BLDC motor using fuzzy logic. This system uses an 8051 microcontroller to achieve this purpose. Here, we constantly monitor the motor’s speed using an IR sensor. The photo-diode is used to keep track of the fan’s motor rotation and measure the RPM. This sensor is integrated with the microcontroller and provides input to the system. The microcontroller then calculates the RPM of motor based on signals provided by the photo-diode. The microcontroller is also integrated with an LCD display to show the status of the system along with the speed of the motor. The fuzzy logic is used in this project to increase and decrease PWM supply based on the RPM of fan monitored to keep it rotating close to the desired speed. Thus, microcontroller constantly provides PWM pulses to keep the motor rotating at the desired speed as per fuzzy logic. Keywords: FUZZY-LOGIC, Motorcontrol, 8051, IR Sensor, LCD

Vibration and acoustic noise of industrial inductors associated to converters in the railway domain

Purpose The purpose of this paper is to present an original study of industrial inductors with different air-gap materials in order to reduce the vibration and noise of inductors. Acoustic comfort is an increasingly important factor at the design stage of industrial inductors associated to converters. In addition, power converters in the railway domain are more and more compact and powerful. Design/methodology/approach Experiments, simulations and test devices were used to determine the main physical phenomena that generate the undesirable audible noise. Electric and vibratory measurements (modal and operational analysis) were compared with the numerical calculations. PWM and sinusoidal supply were taken into account and different prototypes with different materials in the air-gap were built. Findings This study analyzes and details the origin of the electromagnetic noise due to the vertical mode, in order to reduce the vibration and noise of inductors. A detailed analysis using finite element simulation and experimental measurements of free-free mode or forced mode under electrical excitation was conducted to interpret the vibrations of the structure. In addition, in order to observe trends and the impact of magnetostriction effect, the authors propose a simplified model. Practical implications Electric and vibratory measurements (modal and operational analysis) are compared with the numerical calculations. Originality/value This paper gives a response about the origin of the noise with different experimental measurements. Changing the air-gap material is beneficial for the deflection of the inductor. However, it has been presented that, following the shape of the inductor, it is beneficial to reduce or increase the stiffness of the material depending on the column height. For a fixed Young’s modulus air-gap, a ratio Column height/air-gap thickness exists, which makes it possible to cancel the deflection.

A feedforward compensation design in critical conduction mode boost power factor correction for low-power low totalharmonic distortion

For low-power low total harmonic distortion (THD), based on the CSMC 0.5 μm BCD process, a novel boost power factor correction (PFC) converter in critical conduction mode is discussed and analyzed. Feedforward compensation design is introduced in order to increase the PWM duty cycle and supply more conversion energy near the input voltage zero-crossing points, thus regulating the inductor current of the PFC converter and compensating the system loop gain change with ac line voltage. Both theoretical and practical results reveal that the proposed PFC converter with feedforward compensation cell has better power factor and THD performance, and is suitable for low-power low THD design applications. The experimental THD of the boost PFC converter is 4.5%, the start-up current is 54 μA, the stable operating current is 3.85 mA, the power factor is 0.998 and the efficiency is 95.2%.

Overloss coefficient in magnetic laminations during PWM supply voltage

Overloss coefficient in magnetic laminations during PWM supply voltage Author presents an analytical method of calculation of unit power losses in magnetic laminations used in electrical machines and transformers. The idea of this method, based on the solution of Maxwell's equations in the lamination material, was described by the author in the previous work [3], taking into account approximation of constitutive static hysteresis loop by elliptic form of the function B = f(H) depending on magnetic saturation. In the previous formula for new isotropic and anisotropic materials it is needed to introduce so called "anomaly coefficient" deduced from the comparison of measured and calculated value of power losses in arbitrary excitation frequency for assumed induction. The method was tested by comparison with the results of experiments presented in commercial catalogues [1, 2]. Assuming superposition of harmonic power losses it is possible to enlarge this method for the estimation of overloss coefficient in dynamo sheet during axial magnetization with nonsinusoidal flux generated e.g. by PWM voltage supply.

Impact of cut edges on magnetization curves and iron losses in e-machines for automotive traction

At last year's edition of EVS, we presented an improved model for iron losses prediction in Permanent Magnet Synchronous Machines (PMSM) [1]. The benefit of this model holds in that it fits more closely the real material behavior than the standard Steinmetz or Bertotti approaches [2], by including 1) magnetic material characteristics measured at high frequency and 2) an improved representation of iron losses at the approach to saturation (by introducing a higher order term in J). We are taking this model a step further by considering now another phenomenon impacting iron losses in electrical machines: the decrease of magnetic permeability and the increase of local hysteresis loss at the vicinity of lamination edges due to the cutting process. This paper presents a quantitative analysis of the impact of lamination processing (cutting, punching, etc) for high quality low loss electrical steels used in automotive traction applications. It is important to perform the analysis over a wide frequency range, because of the large speed range of PMSM drives in automotive applications and the presence of higher harmonics (PWM supply). Our approach consists in measuring the material characteristics for sample sets with different ratios of degraded vs. non degraded material and at various frequencies. Starting from that experimental data we propose a method to determine the local magnetization curves, as function of distance from the cut edge. These local material characteristics can then be implemented in a FE model so that the effect of punching on the machine performance can be determined quantitatively: (1) the cutting impact on magnetization modification allows more precise field calculations; (2) a proposition is made on the implementation of the cutting impact on the loss calculations in post processing via an enhanced version of the loss model developed in [1].

Iron loss prediction with PWM supply: An overview of proposed methods from an engineering application point of view

The present work compares three different methodologies reported in the literature for the iron loss prediction in magnetic lamination used in apparatus supplied with PWM waveform. The target is the comparison of these methods from an engineering point of view. In particular, the authors analyze the practical use of the methods, such as the measurement and/or calculation procedure difficulties inherent each method. The theoretical approach and the use of these compared methods have been reported in detail and suitable tests have been performed for a correct comparison of the obtained results. The comparison has shown that the methods are similar from the result point of view. As a consequence, from an engineering approach, the three methods can be considered equivalent and the choice of the method to be used can be based only on the measurement facilities available in the test laboratory.

Multi-criteria-based design approach of multi-phase permanent magnet low-speed synchronous machines

A design methodology dedicated to multi-phase permanent magnet synchronous machines (PMSMs) supplied by pulse width modulation voltage source inverters (PWM VSIs) is presented. First, opportunities for increasing torque density using the harmonics are considered. The specific constraints caused by the PWM supply of multi-phase machines are also taken into account during the design phase. All the defined constraints are expressed in a simple manner by using a multi-machine modelling of the multi-phase machines. This multi-machine design is then applied to meet the specifications of a marine propeller: verifying simultaneously four design constraints, an initial 60-pole three-phase machine is converted into a 58-pole five-phase machine without changing the geometry and the active volume (iron, copper and magnet). First, a specific fractional-slot winding, which yields to good characteristics for PWM supply and winding factors, is chosen. Then, using this winding, the magnet layer is designed to improve the flux focussing. According to analytical and numerical calculations, the five-phase machine provides a higher torque (about 15%) and less pulsating torque (71% lower) than the initial three-phase machine with the same copper losses.

Determination of rotor slot number of an induction motor using an external search coil

This paper describes determination of the number rotor slots of an induction motor from the induced emf in an external search coil. This information is needed in prediction of motor speed from the external search coil induced voltage. The approach is based on identifying saliency harmonics and rotor slot harmonics, via FFT analysis of the external search coil emf. The proposed approach is tested on an induction motor driven by the mains supply. The experiments are repeated with a PWM supply. It is shown that the method works well in both cases and the number of rotor slots of the test machine is accurately predicted. .

Iron Loss Prediction With PWM Supply Using Low- and High-Frequency Measurements: Analysis and Results Comparison

In this paper, two different methods for iron loss prediction are analyzed. The first method is based on the classical separation of loss contributions (hysteresis, eddy-current, and excess losses). The model requires loss contribution separation using iron loss measurements with sinusoidal supply. In this paper, this method will be called the ldquolow-frequency method.rdquo The second method, named the ldquohigh-frequency method,rdquo is based on the assumption that, under pulsewidth modulation supply, the higher order flux density harmonics do not influence the magnetic work conditions. These magnetic conditions depend only on the amplitude of the fundamental harmonic of the flux density. In this paper, both the proposed methodologies and the related measurements are described in detail, and the obtained results are compared with the experimental ones. The experimental results show that both methods allow getting excellent results. The high-frequency method is better than the lower one but requires a more complex test bench. Depending on the accuracy required by the user, the more handy method can be chosen, with the guarantee that the estimation errors will be lower than 5%.

Influence of the parameters of power electronic supply on iron losses

The paper investigates the influence of the parameters of the PWM electronic supply on iron losses in ferromagnetic sheets. The analysis is developed both by a numerical model and by experimental investigations on a NO SiFe 2.5%wt 0.65 mm lamination. The numerical approach is based on Finite Element Method and uses the dynamic Preisach model of hysteresis. The measures are performed on an Epstein frame setup. The good agreement between computations and experiments allows the validation of the model, useful for a successive deeper analysis of different PWM supply conditions.