Brushless Excitation System Research Articles

Simulation Model of Brushless Excitation System

Excitation system is key element in the dynamic performance of electric power systems, accurate excitation models are of great importance in simulating and investigating the power system transient phenomena. Parameter identification of the Brushless excitation system was presented. First a block diagram for the EXS parameter was proposed based on the documents and maps in the power station. To identify the parameters of this model, a test procedure to obtain step response, was presented. Using the Genetic Algorithm with the Matlab-software it was possible to identify all the necessary parameters of the model. Using the same measured input signals the response from the standard model showed nearly the same behavior as the excitation system.

A Brushless Exciter Model Incorporating Multiple Rectifier Modes and Preisach's Hysteresis Theory

A brushless excitation system model is set forth that includes an average-value rectifier representation that is valid for all three rectification modes. Furthermore, magnetic hysteresis is incorporated into the d-axis of the excitation using Preisach's theory. The resulting model is very accurate and is ideal for situations where the exciter's response is of particular interest. The model's predictions are compared to experimental results.

Output power limit of 200 MW class brushless superconducting generator excited with magnetic flux-pump

A study on excitation system would be important to enhance potentials of superconducting AC generators. The authors have fabricated a 20 kW class fully superconducting machine with the brushless excitation system which consists of a magnetic flux-pump. By many tests of power generation using this machine, they have investigated theoretically and experimentally the feasibility of the brushless superconducting generator and magnetic flux-pump. Based on these results, this paper proposes the conceptual design and electric characteristics of a practical scale flux pump for an exciter system of a 200 MW class superconducting generator (Super-GM). Furthermore, the paper presents a comparison of output power limits for such as different excitation methods; a persistent field current mode and a conventionally adjusting field current mode.

Output Power Limit and Excitation Method Effect Comparison in Trial Fully Superconducting Generator

A study on efficient excitation system would be important to enhance potentials of superconducting AC generators. Based on such a concept, we have fabricated an experimental machine for actually generating the electricity with a brushless exciter system which consists of a superconducting dynamo or “magnetic flux pump”. The fully superconducting generator has also been studied, in which both of armature and field windings are made of superconductors.We made tests for actual power generation and estimated its static electrical characteristics, resulting in 20kVA class available with not only the conventional excitation system, but also the novel brushless excitation system.The paper presents a comparison of elctrical characteristics in using the brushless excitation method and the external DC current source through brush-slipring system. And the results suggest that the brushless superconducting generator could yield higher output as compared with the conventional excitation.

Modeling of polyphase brushless exciter behavior for failing diode operation

This paper describes an original numerical method for modeling rectified polyphase salient pole synchronous machines which are commonly utilized for large turbo-generator brushless excitation systems. Simulating this kind of system under normal (and especially abnormal) operating conditions, would be of great help for designers and operators in order to improve their reliability and availability. The proposed method is especially convenient to represent actual machines without almost any restrictive assumption. It makes possible the evaluation of the stress of semiconductors when diode failures occur. Results show that good operation of the exciter with short-circuited diodes is almost impossible since its output voltage and current are noticeably weakened. However, its operation can be acceptably maintained if one or more diodes are open.

Fabrication and excitation testing of a fully superconducting brushless generator with magnetic flux pump

Development of a highly efficient excitation system is important in enhancing the potential of superconducting ac generators. A new conceptual design in which electricity is generated with a brushless exciter system using a superconducting dynamo (the magnetic flux pump) has been proposed. Research on a fully superconducting generator using both a superconducting armature and a superconducting field winding has been under way for the past 7 years. In this paper an experimental model of the machine is described and test results on brushless excitation with the magnetic flux pump, with the machine operating as a fully superconducting brushless generator with an estimated capacity of 20 kVA, are presented. © 1997 Scripta Technica, Inc. Electr Eng Jpn. 118 (4): 35–45, 1997

Fabrication and excitation testing of a fully superconducting brushless generator with magnetic flux pump

Development of a highly efficient excitation system is important in enhancing the potential of superconducting ac generators. A new conceptual design in which electricity is generated with a brushless exciter system using a superconducting dynamo (the magnetic flux pump) has been proposed. Research on a fully superconducting generator using both a superconducting armature and a superconducting field winding has been under way for the past 7 years. In this paper an experimental model of the machine is described and test results on brushless excitation with the magnetic flux pump, with the machine operating as a fully superconducting brushless generator with an estimated capacity of 20 kVA, are presented. © 1997 Scripta Technica, Inc. Electr Eng Jpn. 118 (4): 35–45, 1997

Field Tests and Simulation of a High Initial Response Brushless Excitation System

The extremely long transmission distances associated with the Colstrip mine-mouth power plant called for stability improvement measures in the planning stages which included the application of high initial response excitation systems. The brushless excitation systems on the 819 MVA Colstrip Units 3 and 4 are designed to provide high initial response characteristics. Field tests were conducted during unit operation in which the fast large and small-signal response was successfully demonstrated. Response times are similar to that of static systems, without the use of brushes or collectors. Excitation system model constants were calculated based on hardware characteristics. Simulation results show the ability of the model to accurately reproduce the actual excitation system response.

Field Tests and Simulation of a High Initial Response Brushless Excitation System

Field Tests and Simulation of a High Initial Response Brushless Excitation System

Analysis of the Magnetic Field in Rotating Armature Electronically Commutated DC Machines by Finite Elements

A method for analysis of magnetic fields in rotating armature electronically commutated dc machines is presented. The resulting finite element model is suited for analyzing such machines under any load condition, including no-load. The model is used in the analysis and determination of characteristic parameters of such rotating armature machines of the type designed for use in conjunction with modern brushless excitation systems which supply field currents to large turbine generators. The analysis reveals the effect of various load conditions on the values of machine leakage inductances, and emfs. A considerable influence of the load on leakage inductances is determined. The analysis shows considerable reduction in leakage inductance values at higher saturation. This means that such parameters, contrary to prevailing practices, cannot be treated as constant. Interesting similarities (and differences) between the method of analysis of this type of rotating armature electronically commutated dc machines and that of analyzing ordinary synchronous machines is demonstrated clearly in the model development and results. The model is useful in determination of machine equivalent circuit parameters suited for simulation of armature-diode bridge dynamic performances.

A Novel Technique for the Masurement of Average Rotor Temperature of Brushless Synchronous Machines

This paper presents a digital technique for the precise and quick measurement of average temperature of the field winding of a brushless-excitation system. The measurement of voltage and current of the field winding is the by-product of the technique. The device fabricated also incorporates the facility to detect the signle fault to the ground in the field winding. The Rotor temperature has been determined from the precise measurement of change of resistance of the field winding due to temperature rise. The digital display is so calibrated that the aforesaid quantities can be read directly. The technique offers the advantage of direct interfacing with the digital computer, as the data are available in the binary-coded form.

Brushless excitation system for a class of variable-speed synchronous motors

A new brushless excitation system is described for a synchronous motor such as may be used in some forms of variable-frequency inverter-fed drive with rotor-angle control. Transformer primary and secondary windings are incorporated in the stator and rotor, respectively, and the latter winding feeds the field winding via a bridge-rectifier circuit. The transformer primary winding is connected in a series-resonant self-commutated thyristor inverter circuit and the mode of operation of this system is explained. Variation of the firing rate of the inverter, below its maximum operating frequency, controls the excitation current. A special arrangement of two transformer secondary windings is shown by tests to provide rotor excitation that is independent of angular position of the rotor and of its rotational speed. The scheme has unusual operating conditions, particularly in respect of rectifier conduction period and waveforms, and these are explained by both analysis and experiment.

Brushless excitation systems for synchronous machines

This article gives a simple approach to the various commonly used systems of brushless excitation for synchronous machines. The systems described have been designed for medium and large-size motors and generators of the salient-pole type operating at 50 or 60 Hz

A Solid-State Regulator for Electric Utility Applications

An all solid-state regulator with new and improved features over existing regulators has been developed. The new regulator is currently being applied in both brushless excitation systems and static excitation systems for electric utility applications. Solid state circuitry is ideally suited for the application of multiple supplementary control functions required in modern systems. Draw-out modular construction simplifies installation, testing, adjusting, and maintenance of the excitation system components.

The brushless excitation system

A NEW TYPE of excitation system has been developed for use in the electric utility industry in which the generator collector and collector brushes, and the exciter commutator and commutator brushes are eliminated. The basic difference between this system and its predecessors is an a-c exciter mounted on the same shaft as the generator field. This innovation introduces a much shorter exciter time delay due to the fact that a 420-cycle a-c exciter has replaced the conventional d-c exciter which is inherently slower. The smaller time delays make the system easier to stabilize and improve the over-all system response.