JP6271452B2 - Rotating electrical machine system - Google Patents

Description

  Embodiments of the present invention relate to a rotating electrical machine system in which ground current countermeasures are taken in a bearing portion of a rotating shaft.

  A slide bearing is widely used as a bearing for supporting a rotating shaft of a rotating electrical machine. In this slide bearing, an oil film is formed by supplying lubricating oil between the inner periphery of the bearing metal and the outer periphery of the rotating shaft, and the rotating shaft is rotatably supported by this oil film. With respect to such a bearing, it has been proposed to change the characteristics of the bearing by changing the pressure of the lubricating oil supplied to the bearing to reduce the vibration generated in the rotating shaft (for example, see Patent Document 1). .

  By the way, in a rotating electrical machine such as an electric motor driven by a PWM inverter, a ground current is generated due to a neutral point potential fluctuation. That is, when the PWM inverter is switched, a potential fluctuation at an electrical neutral point occurs, and in the motor, a ground current is generated between the stator coil and the ground, and flows as an axial current on the rotating shaft.

  Normally, rotating electrical machines installed on land are easy to ground because they are grounded in the ground, but rotating electrical machines used in ships and the like are grounded under the sea through the hull, making grounding difficult and increasing the shaft current. Tend to. If the shaft current increases, it will affect the equipment connected to the rotating shaft, so countermeasures are required.

  With respect to this axial current, there has been proposed a device for preventing an axial current by flowing a current in the opposite phase to the rotating shaft (see, for example, Patent Document 2). In addition, the shaft current has been dealt with by providing a shaft earth brush or by providing shaft insulation in the bearing.

  There are a wide variety of routes through which such shaft current flows, and in the case of a rotating electrical machine using a slide bearing, the path of stator → frame → bearing bracket → bearing oil film → rotating shaft passes through the bearing oil film to the rotating shaft. There is a flowing route. If the earth current flowing through this route increases, bearing wear due to the earth current may progress, leading to a reduction in bearing life.

  Considering the future increase in switching frequency of the inverter, there may be cases where measures exceeding the insulation treatment by the ground current, which was planned at the product planning stage, may occur in actual operation due to the grounding environment.

JP 2000-120687 A JP-A-60-96150

  As described above, when a large ground current flows through the bearing portion, the life of the bearing is affected.

  Here, the bearing oil film can also be regarded as a kind of electrostatic capacity in a high-frequency circuit, and the oil film formation state of the bearing can be relatively grasped by measuring the axial current.

  The present invention relates to a rotating electrical machine in which the reliability of the bearing is improved by reducing the ground current flowing in the bearing by automatically adjusting the oil film in the bearing of the rotating electrical machine used in an environment where the shaft current changes. The purpose is to provide a system.

  A rotating electrical machine system according to an embodiment of the present invention includes a frame having a stator having a stator core formed in a cylindrical shape, and a columnar shape that forms a fixed gap with the inner periphery of the stator core. A rotor having a rotor core and a rotary shaft integrally provided at the shaft center of the rotor core, the shaft of which is rotatably supported by a bearing provided on an end surface of the frame A hydraulic device that supplies lubricating oil to a portion of the bearing that supports the rotating shaft, and an earth current sensor that measures an earth current flowing from the stator to the rotating shaft through the frame and the bearing. The hydraulic device inputs an earth current value measured by the earth current sensor, and when the earth current value exceeds a predetermined magnitude, the pressure of the lubricating oil supplied to the bearing is increased, and the earth current is increased. Suppression And having an adjustment function of.

  According to the above configuration, the oil film formation state of the bearing is determined from the measurement result of the current flowing through the bearing portion of the rotating electrical machine, the optimum oil film state is maintained by adjusting the hydraulic pressure supplied to the bearing, and the earth current flowing through this portion is reduced. By reducing it, the reliability of the bearing can be improved.

1 is an overall configuration diagram of a rotating electrical machine system according to an embodiment of the present invention. It is a 1/4 sectional view showing the internal configuration of the rotating electrical machine that is the subject of one embodiment of the present invention. It is 1/4 sectional drawing which shows the structure of the bearing used for one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The rotating electrical machine system according to this embodiment monitors the ground current, and when the value is large or increases with time, it is determined that the ground current needs to be suppressed, and the thickness of the bearing oil film is increased. As described above, the shaft order hydraulic pressure is increased, and the oil film formation is adjusted to an optimum state to suppress the ground current.

  First, the overall configuration of the rotating electrical machine system according to this embodiment will be described with reference to FIG. In FIG. 1, reference numeral 11 denotes a rotating electric machine, for example, a motor driven by a PWM inverter. As will be described later, a rotor is provided in the rotating electrical machine 11, and the rotating shaft 12 is rotatably supported by bearings 13 provided on both end faces of the frame 11 a of the rotating electrical machine 11.

  A sliding bearing is used as the bearing 13, and lubricating oil is supplied from the hydraulic device 14. In other words, the hydraulic device 14 includes an oil feed pump 15 and a motor-operated valve 16 that can pump the lubricating oil, and is connected to the bearing 13 via the motor-operated valve 16. The motor-operated valve 16 can adjust the opening of the valve, and by adjusting the valve opening, the inlet pressure of the bearing 13, that is, the hydraulic pressure of the lubricating oil supplied to the bearing 13 can be adjusted to an arbitrary value. it can.

  The bearing 13 is provided with a vibration sensor 18 and a ground current sensor 19. The vibration sensor 18 is configured to be attached to the bearing 13 and monitors the vibration of the bearing 13. The earth current sensor 19 is provided between the frame 11a of the rotating electrical machine 11 and the bearing 13, and measures an earth current flowing through the rotating shaft via the frame 11a and the bearing 13 by driving an inverter.

  In the present embodiment, the hydraulic device 14 receives and monitors the current detected by the ground current sensor 19. When the earth current is large, it is determined that the oil film formation state is insufficient or the earth environment is deteriorated, the opening degree of the motor-operated valve 16 is adjusted, and the inlet pressure of the bearing 13 is increased. This eventually increases the thickness of the bearing oil film and promotes the action of suppressing the ground current.

  As shown in FIG. 2 which is an upper cross-sectional view of the rotating electrical machine 11, a stator 22 and a rotor 23 are provided inside a frame 11a serving as a jacket. The stator 22 has a stator core 24 and a stator winding 25 formed in a cylindrical shape, and is integrally held inside the frame 11a. The rotor 23 has a columnar rotor core 27 and the rotating shaft 12 shown in FIG.

  Although not shown, the rotor core 27 is provided with a rotor bar or the like, and the outer periphery of the columnar iron core is installed so as to form a fixed gap with the inner periphery of the stator core 24. Moreover, the rotating shaft 12 is integrally provided in the axial center part of the rotor core 27, The shaft part is rotatably supported by the bearing 13 provided in the end surface of the flame | frame 11a as mentioned above. In FIG. 2, the bearing 13 is shown only on the right side of the drawing, but as shown in FIG. 1, the shaft portion on the left side of the drawing is naturally supported rotatably by the bearing 13 (not shown).

  As described above, a slide bearing is used as the bearing 13. As shown in FIG. 3, the plain bearing 13 has a bearing metal 31, and the inner periphery thereof is opposed to the outer periphery of the rotating shaft 12 through a minute interval. On the outer peripheral portion of the rotating shaft 12 facing the bearing metal 31, annular seal members 33 and 33 are integrally attached with a distance in the length direction. The sealing materials 33 and 33 are slidably fitted in an annular groove formed on the inner periphery of the bearing metal 31.

  An oil film 34 is formed between the sealing materials 33 and 33, and the rotary shaft 12 is rotatably supported by the oil film 34. That is, the lubricating oil supplied from the hydraulic device 14 shown in FIG. 1 forms an oil film 34 between the sealing materials 33 and 33 described above.

  In the above configuration, the rotating electrical machine (herein, a motor driven by a PWM inverter) 11 is supplied at its rotational speed corresponding to the output frequency of the inverter by supplying power to the stator 22 via the PWM inverter. It drives and drives the apparatus etc. which are connected to the rotating shaft 12 (not shown). At this time, the lubricating oil is supplied from the hydraulic device 14 to the bearing 13 that supports the rotating shaft 12 through the motor-operated valve 16 by the oil feed pump 15, and the inner periphery of the bearing metal 31 and the rotating shaft shown in FIG. An oil film 34 is formed between the outer periphery of the rotary shaft 12 and the rotary shaft 12 is rotatably supported.

  In this operating state, as described above, with the switching of the PWM inverter, the potential fluctuation of the electrical neutral point occurs, an earth current is generated between the stator winding 25 and the ground, and the shaft current is applied to the rotating shaft 12. Flowing as. That is, the stator winding 25 is connected to an inverter circuit (not shown), and ground current is generated between the stator winding 25 and the ground due to the inverter neutral point potential fluctuation due to the influence of switching. Flows as an axial current.

  There are various routes through which this axial current flows, but there are mainly two routes A and B shown in FIG. Of these routes, route A is a route of the stator core 24 → the frame 11 a → the bearing 13 (bearing oil film 34) → the rotating shaft 12 and flows to the rotating shaft 12 via the bearing oil film 34.

  The earth current sensor 19 shown in FIG. 1 measures the earth current flowing through the bearing 13 via the frame 11a by driving the inverter, that is, the earth current flowing through the route A described above. The hydraulic device 14 inputs the earth current value measured by the earth current sensor 19, and when the earth current value exceeds a predetermined magnitude, the pressure of the lubricating oil supplied to the bearing 13 is increased and the earth current is suppressed. . That is, the current detected by the earth current sensor 19 is monitored, and if the earth current is large, it is determined that the oil film 34 is not sufficiently formed or the earth environment is deteriorated, and the opening degree of the motor-operated valve 16 is adjusted to adjust the bearing 13. Increase the inlet pressure. As a result, the bearing oil film 34 is thickened. When the oil film 34 becomes thicker, the capacitance of this portion increases and the resistance value also increases, and the ground current is suppressed.

  Since there is a possibility that rotational vibration increases by increasing the thickness of the bearing oil film 34, bearing vibration monitoring is used together to automatically adjust the oil film to the optimum from the viewpoint of earth current suppression and bearing vibration. That is, the hydraulic device 14 also performs simultaneous monitoring by the vibration sensor 18, measures the bearing vibration accompanying the increase in the thickness of the oil film 34, and adjusts the bearing opening and ground current suppression to the optimum valve opening.

  In the above-described embodiment, a PWM inverter-driven electric motor is exemplified as the rotating electric machine, but the present invention is not limited to this, and can be applied to all rotating electric machines in which a ground current is generated for some reason.

  Although several embodiments of the present invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 11 ... Rotating electrical machine 11a ... Frame 12 ... Rotating shaft 13 ... Bearing 14 ... Hydraulic device 18 ... Vibration sensor 19 ... Ground current sensor 22 ... Stator 23 ... Rotor 24 ... Stator core 25 ... Stator winding 27 ... Rotor Iron core 31 ... Bearing metal 34 ... Oil film

Claims (2)

A frame holding a stator having a stator core formed in a cylindrical shape inside;
A cylindrical rotor core that forms a fixed gap with the inner periphery of the stator core, and a rotary shaft that is integrally provided at the axial center of the rotor core, and the shaft portion of the rotary shaft is the frame. A rotor rotatably supported by a bearing provided on the end surface of
A hydraulic device that supplies lubricating oil to a portion of the bearing that supports the rotating shaft;
An earth current sensor for measuring an earth current flowing from the stator to the rotating shaft via the frame and the bearing;
The hydraulic device inputs an earth current value measured by the earth current sensor, and when the earth current value exceeds a predetermined magnitude, the pressure of the lubricating oil supplied to the bearing is increased and the earth current is suppressed. A rotating electrical machine system characterized by having an adjustment function.   2. The rotating electrical machine system according to claim 1, wherein the hydraulic device adjusts the pressure of lubricating oil supplied to the bearing within a range in which an increase in rotational vibration accompanying the increase in pressure does not exceed a predetermined value.

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