JP2019213373A - Rotary electric machine - Google Patents

Abstract

To obtain a rotary electric machine in which shaft bearing electric erosion is restrained, by reducing the shaft voltage without complicating the structure and the processing, and without impacting on effective magnetic flux.SOLUTION: A rotary electric machine comprises a stator 11 including a stator core 19 having a toric yoke 17 and multiple teeth 18 projecting radially from the inner peripheral surface of the yoke 17 and an armature winding 20 wound around the stator core 19 via an insulator, and formed cylindrically, a rotor 12 placed on the inside of the stator 11, a revolving shaft 13 fixed to the rotor 12, a first bearing 14 and a second bearing 15 supporting the revolving shaft 13 rotatably, an outline 16 supporting the stator 11, the first bearing 14 and the second bearing 15, and a second yoke 60 provided separately from the yoke 17. Lead wires 20U, 20V, 20W of the armature winding 20 are wound around the second yoke 60.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rotating electrical machine including a rotor and a stator.

  In a rotating electrical machine, when a voltage is generated on the rotating shaft due to a neutral point potential fluctuation of the winding, the voltage generated on the rotating shaft is applied to a bearing that supports the rotor. When the voltage applied to the bearing exceeds the dielectric breakdown voltage of the bearing lubricating oil, an erosion phenomenon occurs in which the bearing surface generates heat locally due to discharge and causes melting marks.

  In recent years, rotating electrical machines have been driven by high-frequency inverters, and fluctuations in the neutral point fundamental wave voltage due to the modulation method of the inverter have increased. Moreover, the rectangular wave voltage by switching of an inverter is superimposed on a short cycle, and the peak value is high. Inverter-controlled rotating electrical machines have an increased number of discharges due to an increase in the neutral point fundamental wave voltage and an increase in the peak value. There is a case.

  Patent Document 1 provides an unbalanced magnetic flux that flows in a circumferential direction in an annular yoke by providing a canceling coil that forms a closed circuit by winding the coil together with an annular yoke of a stator and a magnetic core that is provided along with the annular yoke. A method has been proposed in which a current that hinders unbalanced magnetic flux is caused to flow through the cancel coil by inducing a tertiary voltage through the cancel coil to reduce the shaft voltage, thereby suppressing the electrolytic corrosion of the bearing.

JP 2018-26894 A

  However, the invention disclosed in Patent Document 1 requires that three element coils be connected in series in one closed circuit in order to minimize the influence on the rotational torque, so that the structure and processing are complicated. Become. On the other hand, if a closed circuit is constituted by only one element coil, the effective magnetic flux that generates rotational torque is reduced.

  The present invention has been made in view of the above, and it is possible to obtain a rotating electric machine that does not complicate the structure and processing, reduces the shaft voltage without affecting the effective magnetic flux, and suppresses the electrolytic corrosion of the bearing. Objective.

  In order to solve the above-described problems and achieve the object, the present invention provides a stator core having a ring-shaped first yoke and a plurality of teeth protruding radially from the inner peripheral surface of the first yoke, and a fixed core. A stator having an armature winding wound around an iron core via an insulator, formed in a cylindrical shape, a rotor disposed inside the stator, and a rotation shaft fixed to the rotor A first bearing and a second bearing that rotatably support the rotating shaft, a stator, an outer shell that supports the first bearing and the second bearing, and a second yoke provided separately from the first yoke. Prepare. The lead wire of the armature winding is wound around the second yoke.

  According to the present invention, it is possible to obtain a rotating electric machine that does not complicate the structure and processing, reduces the shaft voltage without affecting the effective magnetic flux, and suppresses bearing electrolytic corrosion.

1 is a longitudinal sectional view of a rotary electric machine according to Embodiment 1 of the present invention. Cross section of rotating electric machine according to Embodiment 1 Connection diagram of inverter and winding of rotary electric machine according to Embodiment 1 The figure which shows the fundamental wave waveform of the phase voltage which superimposed the voltage of 3 times the frequency of the rotary electric machine which concerns on Embodiment 1, an interphase voltage, and a neutral point voltage The figure which shows the actual example of the neutral point voltage waveform and bearing voltage waveform of rotary electric machine which concerns on Embodiment 1. Vertical sectional view of the rotating electrical machine according to the second embodiment of the present invention. Vertical sectional view of a rotary electric machine according to Embodiment 3 of the present invention Vertical sectional view of a rotary electric machine according to Embodiment 4 of the present invention Vertical section of a rotating electrical machine according to Embodiment 5 of the present invention

  Below, the rotary electric machine which concerns on embodiment of this invention is demonstrated in detail based on drawing. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
1 is a longitudinal sectional view of a rotating electrical machine according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view of the rotating electrical machine according to the first embodiment. The rotating electrical machine 10 includes a stator 11 formed in a cylindrical shape, a cylindrical rotor 12 disposed inside the stator 11 via a gap, a rotating shaft 13 fixed to the rotor 12, and rotation. A first bearing 14 and a second bearing 15 that rotatably support the shaft 13 are provided. The rotating electrical machine 10 also includes an outer shell 16 that supports the stator 11, the first bearing 14, and the second bearing 15.

  In the first bearing 14, an inner ring 14n is rotatably supported inside the outer ring 14g via a rolling element 14t, and the outer ring 14g is held by a bearing box 16f. In the second bearing 15, an inner ring 15n is rotatably supported inside the outer ring 15g via a rolling element 15t, and the outer ring 15g is held by a bearing box 16r. The rolling elements 14t are held at regular intervals by a holder (not shown). The rolling element 14t rolls in grooves provided in the outer ring 14g and the inner ring 14n, thereby enabling smooth rotation. The rolling elements 15t are held at regular intervals by a holder (not shown). The rolling element 15t rolls in grooves provided in the outer ring 15g and the inner ring 15n, thereby enabling smooth rotation. Lubricating oil such as grease is contained between the outer ring 14g, the rolling element 14t, the cage, and the inner ring 14n, and a thin oil film is formed on the rolling surface to prevent the metal and metal from directly contacting and wearing out. ing. Lubricating oil such as grease is contained between the outer ring 15g, the rolling element 15t, the cage, and the inner ring 15n, and a thin oil film is formed on the rolling surface to prevent the metal and metal from directly contacting and wearing out. ing.

  The stator 11 includes a stator core 19 including a yoke 17 that is an annular first yoke and a plurality of teeth 181, 182, 183, 184, 185, and 186 projecting radially from the inner peripheral surface of the yoke 17. And the armature winding 20. Hereinafter, the whole teeth 181, 182, 183, 184, 185, 186 are referred to as teeth 18. The stator core 19 is made of a magnetic material having a high magnetic permeability. The yoke 17 includes yoke portions 171, 172, 173, 174, 175, and 176. The teeth 18 protrude from the yoke 17 toward the rotor 12. The teeth 181 and the teeth 182 are connected by a yoke portion 171. The teeth 182 and the teeth 183 are connected by a yoke portion 172. The teeth 183 and the teeth 184 are connected by a yoke portion 173. The teeth 184 and the teeth 185 are connected by a yoke portion 174. The teeth 185 and the teeth 186 are connected by a yoke portion 175. The teeth 186 and the teeth 181 are connected by a yoke portion 176. The armature winding 20 is wound around the tooth 18 via an insulator (not shown).

  The stator core 19 is provided with a slot 21 surrounded by a yoke 17 and a tooth 18 for passing the armature winding 20.

  An armature winding 20 composed of six coils U1, V1, W1, U2, V2, and W2 is wound around the teeth 18 and connects the armature winding 20 and an external power source such as an inverter 30. The lead wires 20U, 20V, 20W are wound around a second yoke 60 provided separately from the yoke 17 of the stator core 19. The second yoke 60 is made of a magnetic material having a high magnetic permeability.

  FIG. 3 is a connection diagram of the inverter and the winding of the rotating electrical machine according to the first embodiment. In the U phase, two coils U1 and U2 are connected in series. In the V phase, two coils V1 and V2 are connected in series. In the W phase, two coils W1, W2 are connected in series. The U-phase U1 side, the V-phase V1 side, and the W-phase W1 side are connected to the inverter 30. The U2 side of the U phase, the V2 side of the V phase, and the W2 side of the W phase are joined together to form a neutral point N, and the U phase, the V phase, and the W phase are Y-connected.

  The inverter 30 includes six switching elements 31, 32, 33, 34, 35, and 36 that form arms. A switching element 31 that forms the upper arm and a switching element 34 that forms the lower arm are connected in series to form a first leg. The switching element 32 that forms the upper arm and the switching element 35 that forms the lower arm are connected in series to form a second leg. A switching element 33 that forms the upper arm and a switching element 36 that forms the lower arm are connected in series to form a third leg. The first leg, the second leg, and the third leg are connected to the DC power supply 40 in parallel. An output terminal R protrudes from the first leg and is connected to the U phase of the rotating electrical machine 10. An output terminal S comes out of the second leg and is connected to the V phase of the rotating electrical machine 10. An output terminal T protrudes from the third leg and is connected to the W phase of the rotating electrical machine 10.

  The DC power supply 40 can be obtained by rectifying an AC power supply with a rectifying element and then smoothing it with a capacitor if it is an AC power supply such as a commercial power supply. The DC power supply 40 can be directly obtained from a storage battery as long as it is a DC power supply by an electric vehicle or the like, but the voltage may be adjusted by a DC voltage converter.

  Next, the principle of the generation of electrolytic corrosion of the bearing and the mechanism in which electrolytic corrosion is suppressed in the rotating electrical machine 10 according to the first embodiment will be described.

The inverter 30 is applied with the DC voltage V _DC of the DC power supply 40. The inverter 30 turns on or off the switching elements 31, 32, 33, 34, 35, 36 based on the pulse width modulation signal, and sets the potentials of the output terminals R, S, T to the positive potential VS of the DC power supply 40 and Either one of the negative potentials PSC is connected, or neither is connected. The inverter 30 operates so that the phase difference of the average value of the interphase voltage of the armature winding 20 of the rotating electrical machine 10 becomes a three-phase sine wave voltage shifted by 120 degrees. There are various drive methods for pulse width modulation, such as a trapezoidal wave drive that makes the average value of the fundamental wave of the interphase voltage a sine wave, a trapezoidal wave drive that makes a trapezoid wave, and a rectangular wave drive that makes a rectangular wave In this driving method, when the voltage waveforms at the output terminals R, S, and T are viewed with reference to the potential PSC, a rectangular wave is obtained.

In principle, the pulse width modulation of the sine wave drive is performed by turning on the upper arm of each leg or comparing the lower arm of each leg by comparing the magnitude of a desired sine wave fundamental wave applied to the armature winding 20 and a triangular wave carrier wave. Decide whether to turn on the arm. However, a sine wave having a frequency three times the sine wave voltage applied to the armature winding 20 is superimposed on the phase voltage of each phase in order to make the interphase voltage as large as possible within the range of the DC voltage _VDC. May be compared to a triangular wave carrier.

  When a sine wave having a frequency three times that of the sine wave voltage applied to the armature winding 20 is superimposed on the phase voltage of each phase, the average value of the phase voltage becomes a horseshoe-shaped waveform, but between the phases, the frequency is three times the superimposed frequency. Therefore, the interphase voltage becomes a sine wave voltage.

  FIG. 4 is a diagram illustrating a phase voltage, an interphase voltage, and a fundamental waveform of a neutral point voltage on which a voltage having a frequency three times that of the rotating electrical machine according to the first embodiment is superimposed. The voltages at the output terminals R, S, and T indicate phase voltages of the U phase, the V phase, and the W phase. A voltage between the output terminal R and the output terminal S indicates an interphase voltage between the U phase and the V phase. A voltage between the output terminal S and the output terminal T indicates an interphase voltage between the V phase and the W phase. A voltage between the output terminal T and the output terminal R indicates an interphase voltage between the W phase and the U phase. When a sine wave voltage having a frequency three times that of the sine wave voltage is applied to the armature winding 20, the voltage of the entire armature winding 20 called zero-phase voltage is a sine having a frequency three times that is superimposed. The wave is swung and appears as a neutral point voltage of neutral point N. Due to the zero-phase voltage, a magnetic flux circulating in the circumferential direction is generated in the yoke 17. A shaft voltage due to the electromagnetic induction electromotive force is generated on the rotating shaft 13 penetrating the yoke 17, and a voltage is applied to the oil films of the first bearing 14 and the second bearing 15.

  At this time, as described above, the fundamental wave of the output voltage of the inverter 30 is a sine wave shape. However, since the voltage is a rectangular wave voltage pulse-modulated, the voltage of the entire armature winding 20 actually fluctuates in a rectangular wave shape. doing. Accordingly, a high-frequency rectangular wave voltage having a high peak value is applied to the oil films of the first bearing 14 and the second bearing 15 as compared with the case of only the fundamental wave, and discharge due to dielectric breakdown frequently occurs, and the bearing surface Deterioration progresses rapidly.

  FIG. 5 is a diagram illustrating an example of a neutral point voltage waveform and a bearing voltage waveform of the rotating electrical machine according to the first embodiment. Although it is slower than the neutral point voltage, the shaft voltage induced by the fluctuation of the neutral point voltage is generated with a period of about 60 microseconds.

  Next, the operation of the second yoke 60 around which the lead wires 20U, 20V, 20W of the armature winding 20 are wound will be described.

  As described above, when the shaft voltage due to fluctuations in the neutral point potential exceeds the insulation breakdown voltage between the inner ring 14n, the rolling element 14t, and the outer ring 14g of the first bearing 14, a steep rising discharge current is generated. To do. Similarly, when the shaft voltage due to fluctuations in the neutral point potential exceeds the dielectric strength between the inner ring 15n of the second bearing 15 and the rolling elements 15t and the outer ring 15g, a steep rising discharge current tends to be generated. These discharge currents also appear in the lead wires 20U, 20V, 20W of the armature winding 20. In the rotating electrical machine 10 according to the first embodiment, the lead wires 20U, 20V, and 20W are wound around the second yoke 60 formed of a magnetic material having a high magnetic permeability. It is high. Therefore, in the rotating electrical machine 10 according to the first embodiment, a steep current change is suppressed, and the peak value of the discharge current is suppressed low. As a result, the discharge energy on the bearing surface is also reduced, the amount of heat generation is reduced and melting marks are hardly formed, and the electrolytic corrosion of the first bearing 14 and the second bearing 15 is suppressed.

  The rotating electrical machine 10 according to the first embodiment can suppress the electrolytic corrosion of the first bearing 14 and the second bearing 15 by reducing the shaft voltage without affecting the effective magnetic flux without complicating the structure and processing.

Embodiment 2. FIG.
FIG. 6 is a longitudinal sectional view of the rotating electrical machine according to the second embodiment of the present invention. In the rotating electrical machine 10 according to the first embodiment, lead wires 20U, 20V, and 20W that connect the armature winding 20 and an external power source such as an inverter 30 are provided separately from the yoke 17 of the stator core 19. In the rotary electric machine 10 according to the second embodiment, the cancel wire is connected to the second yoke 60. 22 is wound to short-circuit the winding start and winding end.

  In the rotating electrical machine 10 according to the second embodiment, by winding the cancel line 22 around the second yoke 60, an induced electromotive force due to the fluctuation of the neutral point potential is generated in the cancel line 22, and the neutral point potential is reduced. A current that suppresses fluctuation flows through the cancel line 22. As a result, the shaft voltage is reduced, and the electrolytic corrosion of the first bearing 14 and the second bearing 15 can be suppressed.

Embodiment 3 FIG.
FIG. 7 is a longitudinal sectional view of the rotating electrical machine according to the third embodiment of the present invention. In the rotating electrical machine 10 according to the second embodiment, since the winding start and the winding end of the cancel wire 22 wound around the second yoke 60 are short-circuited, the fundamental frequency component has a low frequency of fluctuation of the neutral point potential. In contrast, a current to be suppressed flows through the cancel line 22. For this reason, in the rotary electric machine 10 according to Embodiment 2, magnetic saturation is likely to occur, and the cross-sectional area of the second yoke 60 needs to be increased. In the third embodiment shown in FIG. 7, the capacitor 50 is connected between the start and end of winding of the cancel line 22.

  In the rotating electrical machine 10 according to the third embodiment, by inserting the capacitor 50 between the start and end of winding of the cancel line 22, the fundamental wave component of the low-frequency neutral point potential hardly flows to the cancel line 22. The rectangular wave component having a high frequency due to the switching of the inverter 30 mainly flows into the cancel line 22, the rectangular wave fluctuation of the neutral point potential is suppressed, and the high frequency discharge in the first bearing 14 and the second bearing 15 is suppressed. And the electric corrosion of the 1st bearing 14 and the 2nd bearing 15 is suppressed. In the rotating electrical machine 10 according to the third embodiment, only the high frequency component flows through the second yoke 60, so that the cross-sectional area of the second yoke 60 can be reduced.

Embodiment 4 FIG.
FIG. 8 is a longitudinal sectional view of the rotating electrical machine according to the fourth embodiment of the present invention. As shown in FIG. 8, the rotating electrical machine 10 according to the fourth embodiment winds a cancel line 23 that detects a change in neutral point potential around the second yoke 60, and connects one end of the cancel line 23 to the first bearing. 14 outer ring 14g or bearing box 16f that is in electrical contact with outer ring 14g and the other end of cancel line 23 is in contact with outer ring 15g of second bearing 15 or bearing box 16r that is in electrical contact with outer ring 15g. Connected to.

  In the rotating electrical machine 10 according to the fourth embodiment, the induced electromotive force generated in the cancel line 23 is similar to the fluctuation of the neutral point potential, is similar to the induced electromotive force generated in the rotating shaft 13, and is similar to the shaft voltage. Therefore, by adjusting the number of windings of the cancel line 23 around the second yoke 60, the fluctuation of the potential of the inner ring 14n of the first bearing 14 and the fluctuation of the potential of the outer ring 14g are brought close to each other. The potential difference with respect to 14 g can be reduced to suppress discharge. Similarly, by adjusting the number of windings of the cancel line 23 around the second yoke 60, the fluctuation of the potential of the inner ring 15n of the second bearing 15 and the fluctuation of the potential of the outer ring 15g are brought close to each other, and the inner ring 15n and the outer ring 15g. The potential difference between and can be reduced to suppress discharge.

Embodiment 5 FIG.
FIG. 9 is a longitudinal sectional view of a rotating electrical machine according to the fifth embodiment of the present invention. In the rotating electrical machine 10 according to the fourth embodiment, the bearing box 16f in which the winding start and the winding end of the cancel wire 23 wound around the second yoke 60 are in electrical contact with the outer rings 14g and 15g or the outer rings 14g and 15g, Since it is directly connected to 16r, a current that suppresses a fundamental wave component having a low frequency of fluctuation of the neutral point potential flows through the cancel line 23. For this reason, the rotary electric machine 10 according to Embodiment 4 is likely to cause magnetic saturation, and the cross-sectional area of the second yoke 60 needs to be increased. In the rotating electrical machine 10 according to the fifth embodiment shown in FIG. 9, a capacitor 50 is disposed between the cancel line 23 and the outer ring 14 g of the first bearing 14.

  In the rotating electrical machine 10 according to the fifth embodiment, the capacitor 50 is inserted between the cancel line 23 and the outer ring 14g of the first bearing 14, so that the fundamental wave component of the fluctuation of the neutral point potential having a low frequency is the cancel line 23. The rectangular wave component having a high frequency due to the switching of the inverter 30 mainly flows to the cancel line 23, the rectangular wave fluctuation of the neutral point potential is suppressed, and the high frequency in the first bearing 14 and the second bearing 15 is suppressed. , And the electrolytic corrosion of the first bearing 14 and the second bearing 15 is suppressed.

  Further, in Embodiments 1 to 4 described above, the rolling bearing has been described as an example, but a type in which an insulating film is formed between the rotating portion and the rotation support portion that rotatably supports the rotation portion. If this bearing is used, electrolytic corrosion can be suppressed. A slide bearing can be exemplified as a bearing in which an insulating film is formed between the rotating portion and the rotation support portion that rotatably supports the rotating portion, but is not limited thereto.

  In the first embodiment, the second embodiment, and the third embodiment, the inverter 30 is a pulse width modulation method and a sine wave applied to the armature winding 20 so that the principle of fluctuation of the neutral point voltage can be easily understood. A method in which a sine wave having a frequency three times the voltage is superimposed on the phase voltage of each phase is compared with a triangular wave carrier wave. However, even when a sine wave of three times the frequency is not superimposed on the phase voltage of each phase, a rectangular wave voltage pulse-modulated from the inverter 30 is applied to the entire armature winding 20 and the neutral point is The present invention is effective because it fluctuates in a rectangular wave shape. The present invention is also effective when the drive system of the inverter 30 is a trapezoidal wave drive or a rectangular wave drive.

  The installation location of the second yoke 60 may be outside or inside the outer shell 16 of the rotating electrical machine 10. Further, the armature windings of the respective phases connected to the neutral point N from the lead wires 20U, 20V, 20W are not required for the second yoke 60, even if the lead wires 20U, 20V, 20W of the armature winding 20 are not used. Any part of 20 may be wound.

  Further, even if the voltage is not supplied from the inverter 30, if the power supply configuration is such that the neutral point voltage fluctuates, there is a possibility that electrolytic corrosion occurs in the first bearing 14 and the second bearing 15 due to the shaft voltage. The present invention can suppress the electrolytic corrosion of the first bearing 14 and the second bearing 15 even when the power supply has a neutral point voltage other than the inverter 30. Further, the present invention can provide the same effect when the armature winding 20 is not a concentrated winding but a distributed winding.

  In each of the above embodiments, a three-phase four-pole permanent magnet synchronous motor has been described. However, the number of phases, the number of poles, and the type of the motor are not limited to the exemplified configurations. That is, the present invention is applicable to any AC motor such as an induction motor or a reluctance motor.

  The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

  DESCRIPTION OF SYMBOLS 10 Rotating electrical machine, 11 Stator, 12 Rotor, 13 Rotating shaft, 14 First bearing, 14g, 15g Outer ring, 14n, 15n Inner ring, 14t, 15t Rolling element, 15 Second bearing, 16 Outer casing, 16f, 16r Bearing box , 17 Yoke, 18,181,182,183,184,185,186 teeth, 19 stator core, 20 armature winding, 20U, 20V, 20W lead wire, 21 slots, 22, 23 cancellation wire, 30 inverter, 31, 32, 33, 34, 35, 36 Switching element, 40 DC power supply, 50 capacitor, 60 Second yoke, 171, 172, 173, 174, 175, 176 Yoke part.

Claims (4)

A stator core having an annular first yoke and a plurality of teeth projecting radially from an inner peripheral surface of the first yoke, and an armature winding wound around the stator core via an insulator A stator formed in a cylindrical shape, a rotor disposed inside the stator, a rotating shaft fixed to the rotor, and a first bearing that rotatably supports the rotating shaft; A second bearing; an outer shell that supports the stator, the first bearing, and the second bearing; and a second yoke that is provided separately from the first yoke,
The rotating electrical machine, wherein the lead wire of the armature winding is wound around the second yoke. A cancel line wound around the second yoke;
The rotating electrical machine according to claim 1, wherein the cancel line is short-circuited between a winding start and a winding end. A cancel line wound around the second yoke;
2. The rotating electrical machine according to claim 1, wherein one end of the cancel line is connected to a rotation support portion of the first bearing, and the other end is connected to a rotation support portion of the second bearing.   The rotating electric machine according to claim 2, further comprising a capacitor inserted in the middle of the cancel line.

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