Structure for reducing shaft voltage of PWM inverter driving type plastic package motor

Abstract

The invention discloses a structure for reducing shaft voltage of a PWM inverter driving type plastic package motor, which relates to the field of motors. In the existing PWM inverter driving type plastic package motor, a high-frequency switch of a power element can cause change of common-mode voltage and parasitic capacitance at each position in the motor, so that a potential difference is generated between an inner ring and an outer ring of a bearing, an oil film of bearing lubricating grease is easily damaged, the bearing is damaged by electrocorrosion, and electrocorrosion generated by theinner ring, the outer ring and a ball is always a key factor influencing the service life of the motor. According to the structure disclosed in the invention, a front end cover and a rear end cover are connected through a conductive piece to realize equipotential, and a capacitor is connected between the conductive piece and a stator core. Effective conduction among the front end cover, the rearend cover and the stator iron core is conveniently realized, the equipotential is formed, the capacitor is arranged between the end cover and the stator core, a proper amount of capacitance is added,and finally, the external induction capacitance of the inner ring and the outer ring of the bearing is balanced, so that the shaft voltage is effectively reduced, the electrocorrosion risk of the bearing is avoided, the service life of the motor is prolonged, and the reliability is improved.

Description

technical field [0001] The invention relates to the field of motors, in particular to a structure for reducing shaft voltage of a PWM inverter-driven plastic-sealed motor. Background technique [0002] In the existing PWM inverter-driven plastic-encapsulated motor, since the stator is plastic-encapsulated and the iron core is insulated from the front and rear end covers, when the PWM inverter drives the motor, the high-frequency switching of the power components will cause changes in the common-mode voltage. Common-mode voltage induction causes parasitic capacitances throughout the motor, and the presence of these parasitic capacitances creates a potential difference between the inner and outer rings of the bearing. The oil film thickness of bearing grease is generally less than 1 μm, and its insulation breakdown voltage is only 5V to more than ten V. Therefore, the peak value of the shaft voltage exceeds the insulation breakdown voltage of the bearing grease oil film, and t...

AI Technical Summary

Problems solved by technology

However, the insulation structure of the rotor is relatively complicated, which interferes with the installation dimensions of the magnetic steel and the shaft, and the plastic insulation layer cannot withstand large torques. In addition, some high-speed and low-torque motor rotors need to directly use integral plastic magnetic rings, which cannot reasonably adjust the electrostatic capacity of the rotor. Therefore, it has an impact on the application range of the motor

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