JPH01194842A - Induction motor - Google Patents

Abstract

PURPOSE:To decrease an eddy-current loss and to reduce lowering in efficiency by covering the outer periphery of a winding with a sheet steel having innumerable through holes and by molding said winding and sheet steel into an integral body. CONSTITUTION:A sheet steel 7 is equipped round from one of axial side faces of a winding 2 to the outer diameter side and is also provided on the winding 2 side with an insulating material 8 between. Further, innumerable through holes 9 are formed in the sheet steel 7 which is molded into an integral body together with a stator core 1 and the winding 2 to form a frame 10. Because a voltage to be applied to the winding 2 is of pulse-type interrupted waveform and contains high-frequency components, harmonic components are also contained in a leakage flux, and a part which did not vibrate at a power frequency starts vibration. However, said harmonic components are electromagnetically shileded by the sheet steel 7, and, therefore, are neither scattered outward of said frame 10 nor generates vibration. Also, a magnetic flux caused by said power frequency diminishes not only an eddy current loss but also lowering in efficiency, because through holes 9 are formed in the sheet steel 7.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an induction motor formed by winding a yoke in a toroidal manner.

``Prior art'' Induction motors are formed by winding a yoke in a toroidal manner, and when the rotation speed is controlled by controlling the phase of the power supply using a phase control element such as a bidirectional thyristor, the windings are used for speed change. This eliminated the need for multiple taps, and the control element was small and relatively inexpensive, making it useful as an induction motor for controlling the rotational speed.

This is especially convenient because the winding structure is simpler than when gears are changed by providing tags on the windings, and the speeds can be changed at any time.

"Problem to be Solved by the Invention" However, when the power supply voltage applied by a phase control element such as a bidirectional thyristor is phase controlled, the applied voltage does not follow a normal sine curve and harmonic components are generated. This causes various vibrations to occur.

For example, it is known that when an induction motor is attached to a steel plate frame, the steel plate receives electromagnetic induction and generates vibrations due to harmonic components.

For this reason, when controlling an induction motor with a phase control element such as a bidirectional thyristor, there is a problem in that electromagnetic shielding is required.

For electromagnetic shielding, as shown in Japanese Utility Model Application No. 61-176948, it is sufficient to interpose a steel plate between the unattached parts, but when the windings are inserted into the teeth of the stator core, Although there is no problem, when a toroidal winding is applied to the yoke as shown in JP-A-59-220040, the magnetic flux of the yoke is structurally directed in a direction different from the direction of the outer diameter than that of the rotor. Because it is easy to leak, the outer periphery promotes leakage of magnetic flux, resulting in a decrease in magnetic flux to the rotor and a decrease in torque.

Therefore, in such a case, it is necessary to provide a steel plate at a position far away from the windings, and as a result, the outer size becomes large, making it unsuitable for downsizing and impractical.

The present invention has been made in view of the above circumstances, and provides effective electromagnetic shielding in an induction motor that controls the rotational speed by controlling the phase of the power supply voltage using a phase control element such as a bidirectional thyristor, and is also compact. It is an object of the present invention to provide an induction motor configured so as not to impair the performance of the invention.

"Means for Solving the Problems" The present invention solves the problems by covering the outer periphery of the windings with a steel plate having numerous through holes and integrally molding the windings and the steel plate.

"Effect" Since countless through holes are formed in the steel plate, eddy current loss due to changes in magnetic flux is reduced, and deterioration in efficiency can be alleviated.

Furthermore, it is possible to prevent the formation of portions where the resin does not flow due to the countless through holes during molding.

``Example'' The present invention will be described based on an example not shown in the drawings. FIG. 1 is a longitudinal cross-sectional view of a main part of a guided lightning type A according to an example of the invention, and FIG. , is a cutaway diagram of the main part thereof.

In the induction motor shown in FIG. 1, a stator 3 is formed by windings 2 wound around a stator core in a toroidal manner, that is, windings are wound around a yoke.

A rotor 4 is provided on the inner diameter side of the stator 3, and is supported by bearings 5a and 5b.
are the brackets 6a attached to the stator 3, respectively.
, 6b.

A steel plate 7 is provided extending from one axial side surface of the winding 2 toward the outer diameter side, and the steel plate 7 has an insulating member 8 interposed on the winding 2 side.

Further, the steel plate 7 has countless through holes 9 formed therein, and is integrally molded with the stator core 1 and the winding 2 using thermosetting resin or the like to form the frame 10.

Further, numerous through holes 9 are formed in the steel plate 7, as shown in FIG.

In such a configuration, in the induction motor, by applying a voltage to the winding 2, the stator core 1' and
By controlling the phase of the voltage applied to the winding 412 using a phase control element such as a bidirectional thyristor, the effective value of the voltage can be lowered, so the torque of the rotor 4 can be lowered and the rotation speed can be controlled. Can be done.

However, on this occasion, $'J! A: Since the voltage changes from a normal sine curve to a phase-controlled waveform that is close to a sawtooth shape and intermittent in a pulse-like manner, it becomes a voltage containing harmonic components and is applied to the winding 2.

When such a waveform is applied to the winding 2, the leakage magnetic flux includes a harmonic component, and the parts that did not vibrate at the power supply frequency begin to vibrate.
The frame 10 will be electromagnetically shielded by
It will no longer diffuse to the outside.

Therefore, even if there is a magnetic material such as a steel plate in the installation part of the induction motor, the magnetic flux will not leak, and no vibration will occur.

In addition, the magnetic flux due to the power frequency is caused by the countless through holes 9 in the steel plate 7.
, which reduces eddy current loss and reduces efficiency.

If such a steel plate 7 comes into contact with the winding 2 and there is a risk of breaking the insulation of the winding 2, an insulating member 8 may be interposed between the steel plate 7 and the winding 2 as in this embodiment. Good □.

The insulating member 8 is formed with through holes in the same manner as the countless through holes 9 formed in the steel plate 7, so that the frame 1
When molding 0, the thermosetting resin can flow through the steel plate 7 and the insulating member 8, so that the winding 2 can be molded well.

"Effects of the Invention J According to the present invention, an induction motor can be constructed using toroidal windings that are easy to downsize, and can be driven by a phase-controlled power source without increasing the external size. Even if there is a problem, it is possible to obtain an induction motor that can be used with peace of mind without causing problems such as vibration in the installation parts.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a main part of an induction motor according to an embodiment of the present invention, and FIG. 2 is a cutaway diagram of the main part. DESCRIPTION OF SYMBOLS 1... Stator core, 2... Winding wire, 4... Rotor, 7... Steel plate, 8... Insulating member, 9... Through hole, 10... Frame.

Claims (1)

[Claims] An induction motor that is formed by winding a yoke in a toroidal shape, and is characterized in that the outer periphery of the winding is covered with a steel plate having numerous through holes, and the winding and the steel plate are integrally molded. .