This paper presents a quantitative analysis of the orthogonal-core type linear variable inductor. The orthogonal-core has wedge gaps for reduction of harmonics of the output currents. The analysis is based on a 3-dimensional nonlinear magnetic circuit of the orthogonal-core. Using the magnetic circuit, one can calculate accurately the operating characteristics of the variable inductor. Furthermore, they develop a VAr compensator for a 6.6 kV AC distribution system using the three-phase variable inductor.

Analysis of orthogonal-core type linear variable inductor and application to VAr compensator

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.

Effects of stator slot magnetic wedges on the induction motor performances

This paper presents a three-phase variable inductor for reactive power control in an electric power system. The variable inductor is constructed with three orthogonal-cores, and is controlled by a simple dc-dc converter. In order to reduce the harmonic currents of the variable inductor, we made a partial gap in the orthogonal-core. The trial three-phase 100 kVA variable inductor demonstrates that the variable inductor can be put to practical use in a 6.6 kV ac distribution system.

Development of 3-phase 100 kVA orthogonal-core type variable inductor with sinusoidal output

A simple magnetic circuit of salient-pole synchronous machines is presented. A method for calculating steady-state electrical performances using the circuit is described. Magnetic saturation including the cross-magnetizing phenomenon is considered in the method. The saturated reactances, field currents, and load angles are calculated easily from the method without much computational effort as compared with the finite element method. Despite the simplicity of the magnetic circuit, the calculated reactances at various load conditions using the method are close to the measured and FEM values.

Steady-state magnetic circuit analysis of salient-pole synchronous machines considering cross-magnetization

This work investigates the effect of the slot opening on the torque and efficiency of a single-phase induction motor. The time-stepping finite element method is used to solve the electromagnetic coupled field in a single-phase induction motor, and then, the Maxwell stress tensor is used to investigate the mechanism of torque production and, eventually, to improve the efficiency. It shows that torque is produced in the vicinity of the slot opening as the rotating magnetic field revolves. It also shows that double layer slots, which have the main and auxiliary windings together, produce a significant amount of negative torque. This research designs the slots of the stator by controlling the slot opening as well as by appropriately introducing slot closure in such a way as to minimize negative torque so that it increases the efficiency of a single-phase induction motor.

Characterization of a single-phase induction motor due to the effect of slot opening

A new variable inductor with sinusoidal output is described. The variable inductor is constructed with a pair of orthogonal cores. The secondary AC current is easily controlled by the primary DC current. The secondary current is almost sinusoidal in a wide control region. A prototype circuit for reactive power compensation using the new variable inductor is presented. >

A new variable inductor for VAR compensation

One method for calculating flux-MMF relationship of an orthogonal core is described. The calculation is based on a three-dimensional magnetic circuit model of the orthogonal core. The model is derived by dividing the orthogonal core, inclusive of the surrounding region, into elements comprising a three-dimensional magnetic circuit. Using this model, the flux-MMF relationship of the orthogonal core with arbitrary dimensions can be calculated from the B-H characteristic of the core material. The calculation method presented is useful for optimum design of devices using an orthogonal core. >

One Method For Calculating Flux-MMF Relations Hip Of Orthogonal-core

In this paper, an analytical method of an orthogonal-core type parametric induction motor is proposed, based on a reluctance network model of the stator. The model is derived by a similar technique applied to an orthogonal-core transformer. Using this model the parametric oscillation characteristic of the motor, without a rotor, is computed. The simulation results agree well with the experiments. It is obvious that the analytical model of the stator presented here is proper for analysis of the motor and that, by use of this model and a suitable analytical model of the rotor, the motor characteristics can be analyzed.

Reluctance network analysis of an orthogonal-core type parametric induction motor

By using an orthogonal-core-type variable inductor and capacitor, we will realize a simple, reliable, and high-quality voltage regulator. However, the nonlinear magnetization characteristic of the orthogonal core causes harmonics in the output current. Last year, in order to reduce the harmonic current of the variable inductor, we proposed an orthogonal core with wedge gaps. A trial three-phase 100 kVA variable inductor demonstrates that the variable inductor can be put to practical use in a 6.6-kV ac distribution system. For wide Appl.ication, it is necessary to establish a design method for the orthogonal core. This paper presents a method of calculating the characteristics an orthogonal core with wedge gaps.

Calculation of the Characteristics of an Orthogonal-Core-Type Variable Inductor with a Wedge Gap.

This paper Presents a method for calculating the nonlinear iron loss in an Orthogonal-core. The authors have analyzed the iron loss by using the 3D magnetic circuit of the orthogonal-core on the reluctance network analysis. The magnetic hysteresis is expressed by the inductances connected in series with reluctances in the circuit in accordance with the Chua-type magnetization model. The computed results approximately agree with experimental ones. It was found that the proposed method is very suitable for calculating the iron loss in an orthogonal-core.

K. Tajima

Papers

A new variable inductor for VAR compensation

One Method For Calculating Flux-MMF Relations Hip Of Orthogonal-core

Reluctance network analysis of an orthogonal-core type parametric induction motor

Calculation of the Characteristics of an Orthogonal-Core-Type Variable Inductor with a Wedge Gap.

Method for Calculating the Iron Loss in an Orthogonal-Core.