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In this article, a novel matrix converter modulation, which minimizes the converter losses is proposed. This approach preserves the same voltage ratio of traditional modulations with a key concept to compute the duty cycles using only the two closest input voltages instead of all three-phase voltages. Compared with Alesina–Venturini modulation, this new strategy achieves higher efficiency due to lower switching losses, in addition to a reduced harmonic content on the output current. Hence, a detailed mathematical treatment based on the knowledge of the output power demand will be shown and discussed. In order to validate the novel modulation, extensive experimental results will be also produced and compared with Venturini's modulation.

According to current energy efficiency labels, the majority of light-emitting diode (LED) lamps on the market are considered as highly efficient devices. This makes it difficult to distinguish between lamps with different operational characteristics and performance. This paper introduces a comprehensive experimental-based labeling methodology for comparing LED lamp performance with reference to two additional important characteristics: light flicker and power factor. The new labeling methodology reveals that there is high diversity between different LED lamps with different circuit topologies but also for a given topology with different design choices. General consumers and design engineers can benefit from the simple and clear information presented by the set of comparative labels when comparing LED lamp performance.

Usually an induction machine with closed slots on the rotor has lower harmonics in stator line currents than that with open slots. However, some induction machines with closed-rotor slots may suffer from local saturation in the rotor slot bridges, and thus, exhibit significant low-order time harmonics in the stator currents. Such phenomenon is revealed with theoretical analysis, and validated with both finite element analysis and experiments. This study is of reference value for the induction machine design so as to avoid the low-order current harmonics.

This paper proposes a method capable of reproducing the particular operating conditions of a hot strip mill and predicting the evolution of the main electrical variables that are involved from both the characteristics of the steel to be milled and the specific features of the rolling mill. The method analyses the load torque and the motor speed evolution in the stands of the roughing and finishing mill drives from the steel to be milled. In this study three types of carbon alloy steel are considered, thus involving dissimilar hardness characteristics. The main stands of the mill, the power network and the filter banks have been modeled. The relationship between the grade of steel and both the electrical demand and various power quality parameters is discussed. The results can be used as a part of an expert system for the automatic estimation of the electrical demand in a hot rolling mill.

This paper is a basic primer for defining and applying active harmonic filters. Active harmonic filters (AHFs) are sophisticated electronic devices that offer significant advantages over traditional harmonic mitigation and displacement power factor correction methods. This paper introduces the AHF and discusses when and where these advantages apply. Additionally, the simplicity in selection of the AHF discussed. The author presents specific examples for the various applications to which AHFs have been applied.

A new method to improve the power factor of three-phase rectifiers is introduced in this paper. The main features of the proposed circuit are low cost, small size, high efficiency, and simplicity. The power factor improvement is achieved with three bi-directional active switches rated at a small fraction of the total processed power, and gated at the line frequency. The principle of operation and design procedure, with a practical example, are also presented. The theoretical analysis was validated with experimental results from a laboratory prototype rated at 7.4 kW and connected to the 220-V 60-Hz AC system. The same circuit was also used in another prototype rated at 12 kW, with similar results.

The use of adjustable-speed drives requires transformers capable of withstanding high levels of harmonic currents under normal operating conditions. Experience has been that overheating problems are much more common with dry-type transformers than with liquid-filled transformers. Transformer insulation life is determined by the hot spot temperature but confirmation of hot spot temperature rise is one performance characteristic which is ignored in industry standards. This is especially important for transformers rated for nonsinusoidal load currents. The design of transformers for nonsinusoidal load currents should include an analysis of the eddy loss distribution in the windings and calculation of the hot spot temperature rise. Calculations and thermal tests giving only average winding temperature rises are not sufficient. Thermal tests with nonsinusoidal currents and measurements of hot spot temperature rises are extremely difficult on large transformers. The combination of testing and analysis may be the only economically practical approach. Analysis indicates that the dry type transformer hot spot temperature is very sensitive to the eddy loss magnitude and distribution. The Underwriters Laboratories Inc. (UL) K-factor rated dry type transformer and the recommended practices given in ANSI/IEEE C57.110 are reviewed. When purchasing transformers subject to nonsinusoidal load currents, considerations should be given to the manufacturer's development program and capability to calculate the eddy loss distribution and hot spot temperatures.

This paper presents a summary of the power quality related concerns associated with the application of electric utility distribution system capacitor banks. These concerns include distribution capacitor switching transients and power system harmonics. Methods for identifying these problems, determining their impact on electric utility and customer systems, and developing suitable solutions are provided. >

Attention has been paid to active filters for power conditioning which provide the following multifunctions: reactive power compensation; harmonic compensation; flicker/imbalance compensation; and voltage regulation. Active filters in a range of 50 kVA-60 MVA have been practically installed in Japan. In the near future, the term “active filters” will have a much wider meaning than it did in the 1970s. For instance, active filters intended for harmonic solutions are expanding their functions from harmonic compensation of nonlinear loads into harmonic isolation between utilities and consumers, and harmonic damping throughout power distribution systems. This paper presents the present status of active filters based on state-of-the-art power electronics technology, and their future prospects and directions toward the 21st Century, including the personal views and expectations of the author

In a number of industrial plants, personnel responsible for the maintenance and design of the electrical power systems have done an excellent job at sizing equipment for connected loads; however, on more than one occasion, those same personnel appeared to be unaware of the interrupting rating for low voltage equipment. This sometimes resulted in electrical power systems that posed hazards to personnel and equipment due to the incorrect application of protective equipment. Several aspects of proper equipment selection based on interrupting ratings are addressed by the author.

The author argues that a good introduction to IEEE Standard 519-1992 (IEEE Recommended Practices and Requirements for Harmonic Control in Electric Power Systems) was made in the original paper (Ellis, see ibid., vol. 32, p. 417-21, 1996), in addition to the presentation of a study case related to an industrial power system. Here, comments are made on the above paper and the original author's reply is also included.

On-line real-time computer and data processing systems such as United Air Lines' Denver Computer Center have many and varying needs. Not only must the electrical power supply be continuous and disturbance-free, but the environmental support systems must not fail. This paper describes a facility, unattended for long periods, which provides for the needs of the people and the expensive equipment associated with that system, even if all outside utilities (except for communications) are lost. The facility, while dually functioning as a dynamic uninterruptible power supply as well as a total energy plant, has been described by some as ``The Friendly Skies' Best Friend.''

Chopper controlled electric rolling stock is maintenance free and can reduce power consumption considerably. Comfort and operating performance are both good. Because of these and other features, such rolling stock is now being widely used. However, there are several problems concerning this equipment, for example, harmonic current, its inductive interference, control system, etc. Therefore careful investigations are needed to solve these problems. This paper deals with the harmonic problems which occurs in chopper controlled electric rolling stock in the case of chopper normal or abnormal operation.