Method for measuring potential of rotating body

Abstract

To provide a method for measuring potential of a rotating body capable of measuring a shaft voltage even in a configuration in which a transmission is attached to a motor without being limited to evaluation of a motor single body.SOLUTION: In a rotary machine 1 including: a stator 2 having winding 21 and generating a magnetic field; a rotor 3 generating rotational torque by the magnetic field generated in the stator 2; and a housing 4 incorporating the stator 2 and the rotor 3, a non-contact potential measurement method measures potential between an electrode pair 11, 12 using the electrode pair 11, 12 fixed to a stator 2 side in the rotary machine 1 and not in contact with the rotor 3. One 11 of the electrode pair 11, 12 is an electrode 11 grounded to the housing 4. The other 12 of the electrode pair 11, 12 is an input electrode 12 having impedance with respect to the housing 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for measuring the potential of a rotating body.

Background Art

[0002] A method for non-contact measurement of the potential of a rotating body is known. For example, the measurement method of a rotating body disclosed in Patent Document 1 is a method for measuring the potential of a motor or a member connected to the motor and rotating. In this method, a non-contact probe made of a conductive material is rotated by a motor and opposed to and separated from the member being rotated to form a capacitance coupling. The non-contact probe is connected to an oscilloscope, and the potential induced in the non-contact probe is measured.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the method disclosed in Patent Document 1 is a method of placing a non-contact probe outside the motor housing for measurement. When the electrode pair is placed with the non-contact probe inside the motor housing, noise from the winding may be picked up and accurate measurement may not be possible. In addition, since a rotating member is attached to the output shaft side of the rotating body, it may not be possible to attach a transmission or the like to the output shaft side of the motor.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a method for measuring the potential of a rotating body that is not limited to the evaluation of a single motor and can measure the shaft voltage even in a configuration in which a transmission or the like is attached to the motor.

Means for Solving the Problems

[0006] A method for measuring the potential of a rotating body according to an aspect of the present invention is a non-contact potential measurement method, which comprises a stator having windings and generating a magnetic field, a rotor generating a rotational torque by the magnetic field generated in the stator, and a housing incorporating the stator and the rotor. In the rotating machine, an electrode pair is provided in the housing of the rotating machine and fixed to the stator side in the rotating machine, and is non-contact with respect to the rotor. One of the electrode pair is an electrode grounded to the housing, and the other of the electrode pair is an input electrode having an impedance with respect to the housing, and the potential between the electrode pair is measured.

Effects of the Invention

[0007] According to the present invention, since the voltage generated in the electrode becomes only the shaft voltage, it can be mounted in the motor housing, so it is not limited to the evaluation of the motor alone, and the shaft voltage can be measured even in a configuration in which a transmission or the like is attached to the motor. A method for measuring the potential of a rotating body can be provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figures 7-14

Figure 15

Figures 16-17

Best Mode for Carrying Out the Invention

[0009] The present inventors have constructed a technique that can measure the shaft voltage not only in a single motor evaluation but also in a configuration where a transmission or the like is attached to the motor by providing an antenna having a guard electrode inside the motor housing. The present invention relates to a technique for preventing a winding voltage, which becomes a noise component with respect to the shaft voltage, from being received by the antenna in order to measure the shaft voltage of the motor in a non-contact manner, and is particularly effective for measuring the shaft voltage of a radial motor having coil ends.

[0010] Preferred embodiments of the present invention will be described with reference to the accompanying drawings. In each figure, those denoted by the same reference numerals have the same or similar configurations. Hereinafter, the present invention will be described in detail with reference to the drawings.

[0011] FIG. 1 is a cross-sectional view showing the structure of a rotating machine 1 according to an embodiment of the present invention. As shown in FIG. 1, the rotating machine 1 includes a stator 2 having a winding 21, a rotor 3 that generates a rotational torque by a magnetic field generated in the stator 2, and a housing 4 that houses the stator 2 and the rotor 3. The potential measurement method of the present embodiment is a non-contact potential measurement method that uses electrode pairs 11 and 12 fixed to the stator 2 side in the rotating machine 1 and non-contact with respect to the rotor 3, and measures the potential between the electrode pairs 11 and 12.

[0012] In the illustrated example, the rotating machine 1 has a resolver as a rotation angle detector 43 that measures the rotation angle of the rotor 3, and a guard electrode 12 described later is fixed to the rotation angle detector  43. By making it integral with the resolver, the noise propagated to the resolver through the winding 21 can be reduced. In the present configuration, an example in which the guide electrode 12 is attached to the resolver is given, but the guide electrode 12 can be provided regardless of the presence or absence of the resolver. The rotating machine 1 may include a bearing 41 that supports the shaft 31 of the rotor 3, a connector 42 that is connected to a power source or an external device, and the like.

[0013] Also, when the rotating machine 1 performs PWM control, assuming that one period of the frequency is t, the capacitance between the antenna 10 and the housing 4 is C, and the internal resistance of the voltage probe used for potential measurement is R, and the initial voltage during the ON period of one cycle is V0 and the final voltage is V1, the formula for discharge is C > -t / {R×ln(V1 / V0)}. Therefore, the measurement accuracy can be improved by attaching a capacitor or resistance value in parallel to obtain the targeted discharge amount. In the case of oil cooling, there is a concern that the capacitance between the input electrode and the housing may change depending on the dielectric constant of the oil. For example, when the capacitance increases by 10 pf, the difference in capacitance increase is smaller for 1000 pf compared to 100 pf in the denominator. Since the relative change in capacitance due to the dielectric constant becomes smaller, the capacitor side has better accuracy. By providing a capacitance between the guard electrode and the non-contact electrode pair, the waveform can be maintained without providing additional components.

[0014] FIG. 2 is a cross-sectional view showing the structure of a modified example of the rotating machine 1 shown in FIG. 1. In the illustrated example, the rotating machine 1 has a temperature measurement unit 44 that measures the temperature inside the rotating machine 1. In such a case, the output voltage may be corrected based on the result of the temperature measurement. According to the modified example, by placing the temperature measurement unit 44 inside the rotating machine 1, it is possible to correct the absolute value in consideration of changes in the dielectric constant of materials such as the coolant 45 like ATF and the substrate due to temperature.

[0015] FIG. 3 is a view showing the front surface of the antenna 10 shown in FIG. 1. FIG. 4 is a view showing the back surface of the antenna 10 shown in FIG. 1. In the illustrated example, the front surface of the antenna 10 faces the rotor 3, and the back surface of the antenna 10 faces the bearing 41. In the rotating machine 1, one of the electrodes 11 of the electrode pair 11, 12 is an electrode grounded to the housing 4, and the other electrode 12 of the electrode pair 11, 12 is an input electrode 12 having an impedance with respect to the housing.

[0016] In the illustrated example, the guard electrode 11 provided between the electrode pair 11, 12 and the winding 21 is used as the electrode 11 grounded to the housing 4. The guard electrode 11 reduces the electrostatic coupling generated between the input electrode 12 and the winding 21. In the illustrated example, the guard electrode 11 faces the input electrode 12, and the input electrode 12 is located between the guard electrode 11 and the rotor 3. Therefore, the voltage generated in the antenna due to the electrostatic coupling with the winding 21 coupled to the back side of the input electrode 12 can be reduced.

[0017] For the guard electrode 11 to detect only the shaft voltage, which is the voltage generated between the shaft and the housing, in an environment where a shaft voltage (S) ±5V is generated when a winding voltage (N) ±200V, which is the voltage generated between the winding and the housing, is input, it is necessary that the shaft voltage (S) received by the input electrode 12 >> the winding voltage (N) received by the input electrode 12. In order to appropriately detect the shaft voltage, it is necessary to design so as to reduce the capacitance on the winding voltage side and make the shaft voltage (S) >> the winding voltage (N). Therefore, paying attention to the fact that the capacitance with the coil end particularly increases due to the positional relationship between the winding and the input electrode 12, a guard electrode 11 for reducing the electrostatic coupling with the coil end is provided.

[0018] In a configuration where a shaft voltage detection antenna is provided in a region surrounded by a winding (coil end) where capacitive coupling is made with the rotor 3 as a location facing the end face of the rotor 3, a noise suppression member for reducing the electrostatic coupling with the coil end is provided in the antenna 10.

[0019] An input electrode 12 having a preset potential is formed on the surface of the antenna 10 facing the rotor 3, and it is formed with an impedance with respect to the housing 4. In the antenna 10, the above-described guard electrode 11 is formed as a noise suppression member. The guard electrode 11 is formed on the back surface opposite to the surface of the antenna 10 facing the rotor 3 and has a lower potential than the input electrode 12. Further, a guard electrode 11 having a lower potential than the input electrode 12 is also formed on the outer periphery of the input electrode 12. The guard electrode 11 is electrically connected to the housing 4 of the rotating machine 1.

[0020] In the illustrated example, the input electrode 12 is non-contact with the end of the shaft 31 of the rotor 3. The input electrode 12 is generally opposed to the end of the shaft 31 of the rotor 3. By providing the torque transmission part, it becomes possible to rotate without problem even if an adhesive or the like is used for the insulating layer. The upper limit value of the torque can be increased. FIG. 5 is a diagram showing a modified example of the antenna 10 shown in FIG. 3. As shown in the figure, the antenna 10 does not have to face the end of the shaft 31 of the rotor 3 over 360 degrees in the entire circumference.

[0021] FIG. 6 is a cross-sectional view showing the structure of the antenna 10 shown in FIG. 1. As shown in FIG. 6, by having the guard electrode 11, the noise of the winding 21 can be reduced. By providing the antenna 10 having the guard electrode 11 inside the housing 4 of the rotating machine 1, it is possible to measure the shaft voltage not only in the evaluation of the rotating machine 1 alone but also in a configuration in which a transmission or the like is attached to the rotating machine 1.

[0022] In the illustrated example, since the guard electrode 11 is located on substantially the same plane as the input electrode 12 and is located on the outer peripheral portion of the input electrode 12, it is possible to guard against the noise from the winding 21 that couples from the circumferential direction of the input electrode 12.

[0023] In the case of the oil cooling method, if oil enters between the electrode and the housing, the capacitance changes and the absolute value of the shaft voltage changes. However, according to the potential measurement method of the present embodiment, since the guard electrode 11 faces the input electrode 12 and the input electrode 12 is located between the guard electrode 11 and the rotor 3, it is possible to guard against the noise from the winding 21 that couples to the back side of the input electrode 12. In the illustrated example, since the solid insulator 13 is filled between the guard electrode 11 and the input electrode 12, the dielectric constant between the electrode and the housing hardly changes.

[0024] FIG. 7-14 is a cross-sectional view showing the structure of a modified example of the antenna 10 shown in FIG. 6. The structure of the antenna 10 according to the present embodiment is not limited to the example shown in FIG. 6 and can be changed as appropriate. For example, as shown in each of FIGS. 7-12, the guard electrode 11 may be a metal structure. When taking a structure such as a substrate, the electric field coupling from the gap of the guard electrode 11 can be blocked.

[0025] For example, as shown in FIGS. 13-14, the capacitance formed between the guard electrode 11 and the input electrode 12 and the time constant calculated from the impedance of the potential measurement component used for potential measurement are made sufficiently small with respect to the time of one cycle of the frequency of the measurement target. The gap between the input electrode 12 and the guard electrode 11 may be configured to have a gap. By giving the guard electrode 11 a capacitance, the waveform can be maintained without additional components.

[0026] FIG. 15 is a circuit diagram showing the measurement principle of the antenna 10. The present researchers found that in the voltage reception circuit, due to the parasitic capacitance C generated between the input electrode 12, the guard electrode 11, and the housing 4 and the resistance R of the probe, CR discharge occurs. As a result, it was found that the shaft voltage may not be correctly received in some cases.

[0027] Also, as discharge suppression means, it has been found that there are means of (1) providing an additional capacitance component between the input electrode 12 and the housing 4 with respect to the capacitance component between the input electrode 12 and the housing, (2) providing an additional resistor between the input electrode 12 and the probe, and (3) providing an operational amplifier in front of the resistor.

[0028] The capacitance component in the above (1) has a capacitance that is sufficiently larger than the capacitance component between the antenna 10 and the housing 4. This "sufficiently larger" means that it also has a sufficient allowable value with respect to the variation of the capacitance component between the antenna 10 and the housing 4. The sufficient allowable value is a capacitance that does not substantially affect the measured value of the shaft voltage.

[0029] Figs. 16-17 are modified examples of the circuit diagram shown in Fig. 15. The circuit diagram of the potential measurement method according to the present embodiment is not limited to the example shown in Fig. 15 and can be changed as appropriate. For example, as shown in Fig. 16, a capacitor may be connected between the input electrode 12 and the housing. For example, as shown in Fig. 17, a resistor may be connected between the input electrode 12 of the electrode pair 11, 12 and the measuring device for measuring the potential of the electrode pair 11, 12. As described above, the potential difference generated in the electrode pair may be stabilized by an operational amplifier.

[0030] According to the potential measurement method of the present embodiment configured as described above, the non-contact potential measurement method uses, in the rotating machine 1, the electrode pair 11, 12 that is fixed to the stator 2 side in the rotating machine 1 and is non-contact with respect to the rotor 3. One of the electrode pair 11, 12 is the electrode 11 grounded to the housing 4, and the other of the electrode pair 11, 12 is the input electrode 12 having impedance with respect to the housing 4. It is possible to provide a potential measurement method for a rotating body that can measure the shaft voltage not only in the evaluation of the rotating machine 1 alone but also in a configuration in which a transmission or the like is attached to the rotating machine 1.

[0031] The embodiments described above are for facilitating the understanding of the present invention and are not for limiting and interpreting the present invention. Each element included in the embodiments and its arrangement, material, conditions, shape, size, etc. are not limited to those illustrated and can be changed as appropriate. Also, it is possible to partially replace or combine the configurations shown in different embodiments.

Explanation of Reference Numerals

[0032] 1... rotating machine, 2... stator, 3... rotor, 4... housing, 10... antenna, 11... guard electrode (an example of a grounded electrode), 12... input electrode, 13... insulator, 21... winding, 31... shaft, 41... bearing, 42... connector, 43... rotation angle detector, 44... temperature measurement unit, 45... coolant.

Claims

1. A stator having windings and generating a magnetic field, a rotor generating a rotational torque by the magnetic field generated in the stator, and a housing containing the stator and the rotor In a rotating electrical machine composed of: Using an electrode pair fixed to the stator side in the rotating electrical machine and non - contact with respect to the rotor, One of the electrode pair is an electrode grounded to the housing, The other of the electrode pair is an input electrode having an impedance with respect to the housing, A non - contact potential measurement method for measuring the potential between the electrode pair.

2. The potential measurement method according to claim 1, wherein the input electrode is generally opposed to an end portion of the axis of the rotor.

3. An electrode that is grounded to the housing and provided between the electrode pair and the windings, The potential measurement method according to claim 1, characterized by having a guard electrode that reduces electrostatic coupling generated between the input electrode and the windings.

4. The guard electrode faces the input electrode, The potential measurement method according to claim 3, wherein the input electrode is located between the guard electrode and the rotor.

5. The potential measurement method according to claim 4, wherein a solid insulator is filled between the guard electrode and the input electrode.

6. The guard electrode is located on substantially the same plane as the input electrode and is located on the outer peripheral portion of the input electrode. The potential measurement method according to claim 3.

7. The potential measurement method according to claim 3, wherein the guard electrode is a metal structure.

8. The rotating electrical machine has a rotation angle detector for measuring the rotation angle of the rotor, The potential measurement method according to claim 3, wherein the guard electrode is fixed to the rotation angle detector. 【Claim The potential measurement method according to claim 1, characterized by connecting a capacitor to the electrode pair.

10. The potential measurement method according to claim 1, characterized by connecting a resistor between the input electrode of the electrode pair and a measuring device for measuring the potential of the electrode pair.

11. The potential measurement method according to claim 1, characterized by stabilizing the potential difference generated in the electrode pair by an operational amplifier.

12. The capacitance formed between the guard electrode and the input electrode, The time constant calculated from the impedance of the potential measurement components used for potential measurement, The potential measurement method according to claim 3, characterized in that a gap between the input electrode and the guard electrode is provided so as to be sufficiently small with respect to the time of one cycle of the frequency to be measured.

13. It has a temperature measurement unit that measures the temperature inside the rotating machine, The potential measurement method according to any one of claims 1 to 12, characterized in that it has a structure for correcting the output voltage based on the result of temperature measurement.

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