Noriyoshi Takahashi

Analytical Model for Magnetic Field Analysis of Induction Motor Performance

A numerical method of calculating the performance characteristics of three phase squirrel cage induction motors, which is based on the magnetic field analysis, is presented. A magnetic field is analyzed over a radial cross-section of a motor with a finite element method. Core saturation and induced rotor bar currents are calculated, and the actual configuration of a motor is analyzed, with this method.

Experimental Study of a Practical AIRGAP Winding Stator Arrangement for Large Turbine Generators

Experimental studies of 2 kA water cooled armature bars composed of fine multi-transposed insulated copper wires and of a special airgap winding stator arrangement in a 4MVA 3 phase generator are carried out. Four different kinds of bar configuration are examined and data fundamental to practical generator applications is obtained. An advanced armature winding configuration, which is called a Skew Winding, and a special winding support system are investigated in the 4MVA generator, and the possibility of practical applications is demonstrated experimentally.

Magnetically anisotropic solid rotor of an induction motor

A conductor, which has magnetically anisotropic and electrically conductive properties, and a magnetically anisotropic solid rotor (matrix rotor) of an induction motor, which uses the conductor, were developed and tested. This conductor is composed of copper-clad steel wires which are aligned in the same direction. This means that the permeability in the direction of the wires is larger than the permeability perpendicular to this direction, and there is good electrical conductivity. These characteristics were confirmed by sample tests. The matrix rotor has a double cylinder structure consisting of a magnetically anisotropic conductor as an outer sheath and a laminated core. The wires are arranged radially so that the outer sheath has a larger radial permeability than circumferential permeability. The matrix rotors of a 0.75 kW induction motor were built for laboratory use. Test results showed that the rotors have less leakage reactance and better characteristics in the heavy load region than a conventional squirrel-cage rotor has. >

Magnetically anisotropic slot wedges for rotating machines

A wedge made of magnetically anisotropic material is proposed, which can be applied to the stator of rotating machines. The authors present magnetic field analyses performed with a two-dimensional (2-D) finite element method and describe the characteristics of the analyzed flux distribution. By using such wedges, the ripple of the flux distribution and the leakage flux decrease are compared with those of machines using magnetically isotropic wedges. >

Test Results of Motors with a Superconducting Rotor

Experimental studies of two-pole, three-phase superconducting motors using Y-Ba-Cu-0 (high-Tc) and Nb3Sn rotors were carried out. The former high-Tc rotor shapes were cylindrical, cylindrical with axial slits, or reluctance types. The rotor outer diameters were 38mm and their lengths were 30–32mm. Each high-Tc rotor started to rotate by itself and kept a speed with a large slip at superconducting conditions in liquid nitrogen. For example, the cylindrical rotor rotated at 46 rpm when the motor was excited by a 5 Hz sinusoidial alternating current of 1.5 VA input.

A HELICAL AIRGAP WINDING FOR SUPERCONDUCTING GENERATORS

Applications of a helical winding to superconducting generator stators have been examined in several research institutes. This winding makes a simpler stator end configuration possible. However, the peripheral component of the helical armature current may produce additional eddy current loss and heating in the laminated stator core and superconducting rotor. This paper describes these problems and presents a three dimensional magnetic field analysis using the case of a 50MVA stator applied helical airgap winding.