Motor and electric device equipped with same

Abstract

A motor according to the present invention comprises: a stator including a stator core with a winding wound therearound; a rotor including a rotating body circumferentially holding a permanent magnet facing the stator, and a shaft passing through the center of the rotating body and fastened to the rotating body; two bearings for supporting the shaft; and two conductive brackets electrically insulated from each other and respectively securing the bearings thereto. In the motor, the electrostatic capacitance (A) between the stator core and one bracket and the electrostatic capacitance (B) between the stator core and the other bracket are set approximately equal or equal to each other. Further, the motor has the following relationship between the electrostatic capacitance (A) and the electrostatic capacitance (B): 0.4A <= B <= 2.5A

Description

technical field [0001] The present invention relates to an electric motor, and more particularly to an electric motor improved to suppress electrical corrosion of bearings. Background technique [0002] In recent years, a method of driving a motor by an inverter of a pulse width modulation (PulseWidthModulation) method (hereinafter referred to as a PWM method) has been adopted more and more. In the case of such a PWM type inverter drive, the neutral point potential of the winding is not zero, so a potential difference (hereinafter referred to as shaft voltage) is generated between the outer ring and the inner ring of the bearing. The shaft voltage includes high-frequency components generated by switching, and when the shaft voltage reaches the breakdown voltage of the oil film inside the bearing, a tiny current flows through the inside of the bearing, causing electrical corrosion inside the bearing. In the case where electro-corrosion progresses, a wavy wear phenomenon some...

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Problems solved by technology

Therefore, if the conventional structure of electrically connecting the stator core of the motor, etc., to the ground wire of the earth is adopted and the problem is solved by adding the structure of the structure, then from the viewpoint of the specifications and characteristics of the motor, it will be further improved. There are difficulties in investigating other topics

[0013] In addition, in the method of electrically shorting the two end caps, providing a dielectric layer on the rotating body, and changing the electrostatic capacity to reduce the shaft voltage, the following problems have been considered: short-circuiting the lead wire between the two end caps, conduction The belt is cut during the production process of the motor or during the use of the motor, and the balance of the shaft voltage in the two end caps collapses and galvanic corrosion occurs

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