Motor control unit, motor and pump device

Abstract

The present invention provides a motor control unit capable of suppressing noise generated by a motor, a motor having the motor control unit, and a pump device having the motor. The motor control unit includes: a drive voltage line that supplies a drive voltage to an inverter; a common line connected to the neutral point of a three-phase coil; an inductor electrically connected in series with the drive voltage line; a first capacitor electrically connected between a portion of the drive voltage line between the inverter and the inductor and ground; a second capacitor electrically connected between a portion of the drive voltage line closer to the input side than the first capacitor and ground; and a third capacitor electrically connected between the second capacitor and ground. The common line is electrically connected between the second and third capacitors.

Description

Technical Field

[0001] The present invention relates to an electric motor used in a pump device, etc. The present invention also relates to a motor control unit for controlling the electric motor, the electric motor, and the pump device. Background Art

[0002] Patent Document 1 discloses a pump device. The pump in this document includes an electric motor, an impeller fixed to the rotor of the electric motor, and a housing that houses the impeller and defines a pump chamber. The electric motor includes a rotor that can rotate about a central axis and a stator with a three-phase coil.

[0003] As the motor for the pump device, a motor with noise suppression measures is sometimes used (for example, see Patent Document 2). The motor disclosed in Patent Document 2 includes a control device comprising a capacitor connected in parallel between the neutral point of the three-phase coil and a preset reference potential. The capacitor smoothes the voltage at the neutral point, thereby suppressing noise generated by the motor.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-159336

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2001-352792 Summary of the Invention

[0008] Technical problem to be solved by the invention

[0009] Pump devices are increasingly being used with other precision equipment. When used in applications such as vehicle-mounted pumps, there is a need to further suppress the noise generated by the pump device's motor. In such cases, using only the motor disclosed in Patent Document 2 in a pump device is insufficient as a noise countermeasure.

[0010] Therefore, the technical problem of the present invention is to provide a motor control unit capable of suppressing noise generated by the motor. In addition, a motor having the motor control unit and a pump device having the motor are provided.

[0011] Technical solutions used to solve technical problems

[0012] In order to solve the above technical problems, the motor control unit of the present invention controls a motor having a three-phase coil, and comprises: a motor control unit, which controls the rotation of the motor through a control signal; an inverter, which applies a driving voltage supplied from a driving power supply to the three-phase coil according to an output signal from the motor control unit; a driving voltage line, which supplies the driving voltage to the inverter; a common line, which is electrically connected to the neutral point of the three-phase coil; an inductor, which is electrically connected in series with the driving voltage line; a first capacitor, which is electrically connected between a portion of the driving voltage line between the inverter and the inductor and ground; a second capacitor, which is electrically connected between a portion of the driving voltage line closer to the input side than the first capacitor and ground; and a third capacitor, which is electrically connected between the second capacitor and ground, and the common line is electrically connected between the second capacitor and the third capacitor.

[0013] The present invention includes an inductor electrically connected in series with a drive voltage line, and a first capacitor electrically connected between a portion of the drive voltage line between the inverter and the inductor and ground. This configuration smoothes the drive voltage flowing through the drive voltage line, thereby suppressing noise generated by the drive voltage line.

[0014] Furthermore, the present invention includes a second capacitor and a third capacitor. The second capacitor is electrically connected between the portion of the drive voltage line closer to the input side than the first capacitor and ground, and the third capacitor is electrically connected between the second capacitor and ground. A common line is electrically connected between the second and third capacitors. With this configuration, the neutral point electrically connected to the common line is clamped by the second and third capacitors. This allows the voltage to be smoothed even when a relatively large voltage amplitude is generated at the neutral point. This suppresses noise generated by the motor.

[0015] In the present invention, it is preferred that, if the electrostatic capacitance of each of the second capacitor and the third capacitor is C1, the following conditional expression is satisfied: 0.047μF ≤ C1 ≤ 0.33μF. However, if the electrostatic capacitance C1 of each of the second capacitor and the third capacitor is less than 0.047μF, the voltage at the neutral point cannot be sufficiently smoothed, and the effect of reducing the noise generated by the motor is relatively low. In addition, if the electrostatic capacitance C1 of each is greater than 0.33μF, the voltage at the neutral point is excessively smoothed, and the rotation characteristics of the motor are relatively reduced. As a result, it is difficult to exert the performance of the motor. Therefore, if the electrostatic capacitance C1 of each of the second capacitor and the third capacitor satisfies 0.047μF ≤ C1 ≤ 0.33μF, the rotation characteristics of the motor can be prevented from being reduced, and the noise generated by the motor can be suppressed.

[0016] In the present invention, the second capacitor is preferably electrically connected between a portion of the drive voltage line closer to the input side than the inductor and ground. This configuration achieves a greater effect on suppressing noise generated by the motor than a case where the second capacitor is electrically connected between a portion of the drive voltage line closer to the output side than the inductor and ground.

[0017] In the present invention, it is preferred that, if the electrostatic capacitance of the first capacitor is C2, the following conditional formula is satisfied: 100μF≦C2. In the case where the electrostatic capacitance C2 of the first capacitor is less than 100μF, the current ripple tends to become relatively large, and the driving voltage flowing through the driving voltage line cannot be sufficiently smoothed. Therefore, it is difficult to effectively suppress the noise generated by the driving voltage line. Therefore, if the electrostatic capacitance C2 of the first capacitor satisfies 100μF≤C2, the noise generated by the voltage line can be suppressed. In addition, since the current ripple is suppressed, the first capacitor will not overheat. Therefore, the characteristics and reliability of the first capacitor can be ensured.

[0018] The present invention preferably includes a control signal line for inputting the control signal to the motor control unit, and a fourth capacitor electrically connected between the control signal line and ground. This configuration smoothes the control signal transmitted via the control signal line, thereby removing noise generated by the control signal line.

[0019] The present invention preferably includes: a ferrite bead electrically connected in series with the control signal line at a portion of the control signal line closer to the input side than the fourth capacitor; and a sixth capacitor electrically connected between the portion of the control signal line closer to the input side than the ferrite bead and ground. This configuration further reduces noise generated by the control signal line.

[0020] The present invention preferably includes an FG output line for transmitting a rotational speed signal corresponding to the rotational speed of the motor to an external device; and a fifth capacitor electrically connected between the FG output line and ground. This configuration smoothes the rotational speed signal transmitted by the FG output line, thereby eliminating noise generated by the FG output line.

[0021] In the present invention, it is preferred that, when the electrostatic capacitance of the fifth capacitor is C3, the following conditional expression is satisfied: C3 ≤ 0.1 μF. When the electrostatic capacitance C3 of the fifth capacitor is greater than 0.1 μF, the noise generated by the FG output line can be removed, but the output waveform of the speed signal is relatively blunt. Therefore, the external device cannot detect the speed signal of the motor with high precision, making it difficult to control the motor to the desired speed. Therefore, if the electrostatic capacitance C3 of the fifth capacitor satisfies C3 ≤ 0.1 μF, the noise generated by the FG output line can be removed, and the motor can be controlled to the desired speed.

[0022] The present invention provides an electric motor comprising: a rotor rotatable about a central axis; a stator equipped with a three-phase coil; and the above-described electric motor control unit. With this configuration, noise generated by the electric motor can be suppressed.

[0023] The present invention provides a pump device comprising: the aforementioned electric motor; an impeller fixed to the rotor; and a housing that houses the impeller and defines a pump chamber. This configuration suppresses noise generated by the pump device, thereby minimizing the impact of noise on precision equipment used around the pump device.

[0024] Effects of the Invention

[0025] According to the present invention, the drive voltage flowing through the drive voltage line is smoothed by the inductor and the first capacitor, thereby suppressing noise generated by the drive voltage line. Furthermore, since the neutral point electrically connected to the common line is clamped by the second and third capacitors, the voltage can be smoothed even when a voltage with a large amplitude is generated at the neutral point. Consequently, the motor control unit can suppress noise generated by the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is an explanatory diagram schematically showing a cross section of a pump device according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic circuit diagram of the motor control unit.

[0028] Figure 3 (A) Figure 3 (B) and Figure 3 (C) is a graph comparing the electrostatic capacitance of capacitors.

[0029] Description of Reference Numerals

[0030] 1…Pump device; 2…Motor; 3…Impeller; 4…Casing; 4A…Pump chamber; 5…Rotor; 6…Three-phase coil; 7…Stator; 8…Resin seal member; 9…Circuit board; 10…Motor control unit; 11…Motor control unit; 12…Inverter; 13…Drive voltage line; 14…Common line; 15…Control signal line; 16…Output line; 17…Ground line; 18…Inductor; 19…Ferrite magnet;

[0031] 21…first capacitor; 22…second capacitor; 23…third capacitor; 24…fourth capacitor; 25…fifth capacitor; 26…sixth capacitor; 61…U-phase coil; 62…V-phase coil; 63…W-phase coil; 65…neutral point; 100…ground DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 : is an explanatory diagram schematically showing a cross section of a pump device according to an embodiment of the present invention. Figure 1 As shown, the pump device 1 includes: a motor 2 having a rotor 5 rotatable about a central axis L; an impeller 3 fixed to one side L1 of the central axis L relative to the rotor 5; and a housing 4 that houses the impeller 3 and defines a pump chamber 4A. The housing 4 is attached to the motor 2 from one side L1. The pump device 1 moves the fluid within the pump chamber 4A by rotating the impeller 3 and rotor 5 integrally about the central axis L.

[0033] The motor 2 includes a rotor 5 rotatable about a central axis L; a stator 7 including a three-phase coil 6; a resin seal 8 covering the stator 7; and a circuit board 9 connected to the three-phase coil 6. The motor 2 is a three-phase motor, and the three-phase coil 6 includes a U-phase coil, a V-phase coil, and a W-phase coil. A magnet is provided on the outer circumference of the rotor 5.

[0034] The circuit board 9 is located on the other side L2 of the stator 7. A motor control unit 10 for controlling the motor 2 is formed on the circuit board 9. The motor control unit 10 controls the rotation of the motor 2 by controlling the power supply to the three-phase coil 6.

[0035] Figure 2 1 is a schematic circuit diagram of the motor control unit 10. Figure 2 As shown, the motor 2 controlled by the motor control unit 10 includes a U-phase coil 61, a V-phase coil 62, and a W-phase coil 63. The three-phase coils 6 are connected in a star shape.

[0036] The motor control unit 10 includes a motor control unit 11 that controls the rotation of the motor 2 using a PWM signal; an inverter 12 that applies a drive voltage supplied from a drive power supply to the three-phase coil 6 based on an output signal from the motor control unit 11; a drive voltage line 13 that supplies the drive voltage to the inverter 12; and a common line 14 connected to the neutral point 65 of the three-phase coil 6. The motor control unit 10 also includes a control signal line 15 for inputting a PWM signal from an external device into the motor control unit 11; and an FG output line 16 for transmitting a rotational speed signal corresponding to the rotational speed of the motor 2 to the external device.

[0037] The motor control unit 10 includes an inductor 18 , a first capacitor 21 , a second capacitor 22 , a third capacitor 23 , a fourth capacitor 24 , a fifth capacitor 25 , a sixth capacitor 26 , and a ferrite bead 19 .

[0038] The motor control unit 11 is composed of an IC chip or the like disposed on the circuit board 9. Based on a PWM signal input from an external device, the motor control unit 11 outputs an output signal for controlling the inverter 12. Furthermore, the motor control unit 11 outputs a speed signal corresponding to the rotational speed of the rotor 5 to the external device. Based on the speed signal, the external device outputs a PWM signal to the motor control unit 11 to adjust the motor 2 to the desired rotational speed.

[0039] Inverter 12 includes switching elements Q1 and Q2 forming upper and lower arms for the U phase, switching elements Q3 and Q4 forming upper and lower arms for the V phase, and switching elements Q5 and Q6 forming upper and lower arms for the W phase. Each of switching elements Q1 to Q6 is, for example, a MOS FET.

[0040] The drains of switching element Q1, switching element Q3, and switching element Q5 are connected to drive voltage line 13. The sources of switching element Q2, switching element Q4, and switching element Q6 are connected to ground 100 via shunt resistor Rs. Both ends of shunt resistor Rs are connected to motor control unit 11 via resistors R33 and R34 from output lines 121 and 122.

[0041] The source of switching element Q1 and the drain of switching element Q2 are connected to U-phase coil 61 of three-phase coil 6. The source of switching element Q3 and the drain of switching element Q4 are connected to V-phase coil 62 of three-phase coil 6. The source of switching element Q5 and the drain of switching element Q6 are connected to W-phase coil 63 of three-phase coil 6.

[0042] Capacitor 51 is connected to the source of switching element Q1 and the drain of switching element Q2 on the side opposite to the side connected to U-phase coil 61 of three-phase coil 6. Capacitor 52 is connected to the source of switching element Q3 and the drain of switching element Q4 on the side opposite to the side connected to V-phase coil 62 of three-phase coil 6. Capacitor 53 is connected to the source of switching element Q5 and the drain of switching element Q6 on the side opposite to the side connected to W-phase coil 63 of three-phase coil 6. Capacitors 51-53 serve as charging and discharging capacitors for the bootstrap circuit.

[0043] Bootstrap diodes D31 to D33 are connected between the capacitors 51 to 53 and the motor control unit 11 , respectively. The diodes D31 to D33 are connected to the motor control unit 11 via a resistor R31 .

[0044] Resistors R11 to R16 are connected between the gates and sources of switching elements Q1 to Q6, respectively. Resistors R21 to R26 are connected between the gates of each switching element Q1 to Q6 and the motor control unit 11, respectively. Filters 41 to 46 are connected between the drains and sources of switching elements Q1 to Q6, respectively. Filters 41 to 46 are composed of resistors and capacitors connected in series.

[0045] Inverter 12 is a circuit that converts the drive voltage supplied from drive voltage line 13 into three-phase AC by switching switching elements Q1 to Q6, and then causes the three-phase AC drive voltage to flow through motor 2, thereby rotating rotor 5 of motor 2. Inverter 12 drives motor 2 based on an output signal from motor control unit 11.

[0046] The drive voltage line 13 supplies power to the motor control unit 11 and the inverter 12. In this embodiment, a rated voltage of 12V is applied to the drive voltage line 13. An inductor 18 and a first capacitor 21 are connected to the drive voltage line 13. The inductor 18 is electrically connected in series with the drive voltage line 13. The first capacitor 21 is electrically connected between the portion of the drive voltage line 13 between the inverter 12 and the inductor 18 and ground. In this embodiment, the electrostatic capacitance C2 of the first capacitor 21 is 150μF.

[0047] A capacitor 27 and a diode 31 are connected to the driving voltage line 13. The capacitor 27 is electrically connected between a portion of the driving voltage line 13 closer to the output side than the first capacitor 21 and the ground 100. The diode 31 is electrically connected between a portion of the driving voltage line 13 between the inductor 18 and the first capacitor 21 and the ground 100.

[0048] A first line 131 and a second line 132 are connected to the drive voltage line 13. The first line 131 and the second line 132 are electrically connected to the motor control unit 11, supplying power to the motor control unit 11. The first line 131 branches off on the output side of the capacitor 27 and is electrically connected to the motor control unit 11. The first line 131 is connected to a capacitor 28 electrically connected to the ground 100. The second line 132 is electrically connected to the motor control unit 11 via a resistor R32.

[0049] A second capacitor 22 is connected to the driving voltage line 13. The second capacitor 22 is electrically connected between a portion of the driving voltage line 13 that is closer to the input side than the first capacitor 21 and the ground. More specifically, the second capacitor 22 is electrically connected between a portion of the driving voltage line 13 that is closer to the input side than the inductor 18 and the ground. The third capacitor 23 is electrically connected between the second capacitor 22 and the ground 100. That is, the second capacitor 22 and the third capacitor 23 are connected in series between the driving voltage line 13 and the ground 100 on the input side than the inductor 18 in the driving voltage line 13. In this embodiment, the second capacitor 22 and the third capacitor 23 are composed of the same capacitor. That is, the electrostatic capacitance C1 of the second capacitor 22 is the same as the electrostatic capacitance C1 of the third capacitor 23. The electrostatic capacitance C1 of each of the second capacitor 22 and the third capacitor 23 is 0.1μF.

[0050] Here, common line 14 is electrically connected between second capacitor 22 and third capacitor 23. That is, neutral point 65 electrically connected to common line 14 is clamped by second capacitor 22 and third capacitor 23. In addition, ground line 17 is connected between third capacitor 23 and ground 100.

[0051] The control signal line 15 transmits a PWM signal from an external device to the motor control unit 11. A ferrite bead 19, a fourth capacitor 24, a sixth capacitor 26, and a resistor R3 are connected to the control signal line 15. The fourth capacitor 24 is electrically connected between the control signal line 15 and ground 100. The ferrite bead 19 is electrically connected in series with the control signal line 15 at a portion closer to the output side of the control signal line 15 than the fourth capacitor 24. The sixth capacitor 26 is electrically connected between a portion of the control signal line 15 closer to the output side than the ferrite bead 19 and ground 100. The resistor R3 is electrically connected in series with the control signal line 15 at a portion closer to the output side than the sixth capacitor 26.

[0052] The control signal line 15 is connected to a third line 151 connected to the first line 131. The third line 151 is electrically connected to the control signal line 15 between the ferrite bead 19 and the resistor R3. The third line 151 is electrically connected in series with the resistor R2.

[0053] The FG output line 16 transmits the motor 2 speed signal output from the motor control unit 11 to an external device. A fifth capacitor 25, a resistor R1, and a NOT gate Q7 are connected to the FG output line 16. The fifth capacitor 25 is electrically connected between the FG output line 16 and ground 100. The portion of the FG output line 16 that is closer to the input side than the fifth capacitor 25 is electrically connected in series with the FG output line 16. The NOT gate Q7 is electrically connected in series with the FG output line 16 that is closer to the input side than the resistor R1 is with the FG output line 16. In this embodiment, the electrostatic capacitance C3 of the fifth capacitor 25 is 0.047 μF.

[0054] Effects

[0055] The motor control unit 10 of this embodiment includes an inductor 18 electrically connected in series with the drive voltage line 13, and a first capacitor 21 electrically connected between the portion of the drive voltage line 13 between the inverter 12 and the inductor 18 and the ground 100. This configuration smoothes the drive voltage flowing through the drive voltage line 13, thereby suppressing noise generated by the drive voltage line 13.

[0056] Furthermore, the motor control unit 10 of this embodiment includes a second capacitor 22 electrically connected between a portion of the drive voltage line 13 closer to the input side than the first capacitor 21 and ground 100; and a third capacitor 23 electrically connected between the second capacitor 22 and ground 100. The common line 14 is electrically connected between the second capacitor 22 and the third capacitor 23. Therefore, since the neutral point 65 electrically connected to the common line 14 is clamped by the second capacitor 22 and the third capacitor 23, even when a relatively large voltage is generated at the neutral point 65, the voltage can be smoothed. This suppresses noise generated by the motor 2. Furthermore, since the second capacitor 22 is electrically connected between a portion of the drive voltage line 13 closer to the input side than the inductor 18 and ground 100, the noise generated by the motor 2 is more effectively suppressed than when the second capacitor 22 is electrically connected between a portion of the drive voltage line 13 closer to the output side than the inductor 18 and ground 100.

[0057] The motor control unit 10 of this embodiment includes a control signal line 15 for inputting a PWM signal from an external device into the motor control unit 11, and a fourth capacitor 24 electrically connected between the control signal line 15 and ground 100. This smoothes the PWM signal transmitted along the control signal line 15, thereby eliminating noise generated by the control signal line 15. Furthermore, the motor control unit 10 of this embodiment includes a ferrite bead 19 electrically connected in series with the control signal line 15, on the output side of the control signal line 15 relative to the fourth capacitor 24, and a sixth capacitor 26 electrically connected between the output side of the control signal line 15 relative to the ferrite bead 19 and ground 100. This configuration further eliminates noise generated by the control signal line 15.

[0058] The motor control unit 10 of this embodiment includes an FG output line 16 for transmitting a rotational speed signal corresponding to the rotational speed of the motor 2 to an external device, and a fifth capacitor 25 electrically connected between the FG output line 16 and the ground 100. This allows the rotational speed signal transmitted via the FG output line 16 to be smoothed, thereby removing noise generated by the FG output line 16.

[0059] Here, the electrostatic capacitances of the first capacitor 21 , the second capacitor 22 , the third capacitor 23 , and the fifth capacitor 25 will be described. Figure 3 (A) Figure 3 (B) and Figure 3 (C) is a graph comparing the electrostatic capacitance of capacitors.

[0060] like Figure 3 As shown in (A), when the electrostatic capacitance C2 of the first capacitor 21 is less than 100 μF, the current ripple tends to become relatively large, and the drive voltage flowing through the drive voltage line 13 cannot be sufficiently smoothed. Therefore, it is difficult to effectively suppress the noise generated by the drive voltage line 13. Therefore, in this embodiment, since the electrostatic capacitance C2 of the first capacitor 21 is 150 μF, 100 μF ≤ C2 is satisfied, and thus the noise generated by the drive voltage line 13 can be suppressed. In addition, since the current ripple is suppressed, the first capacitor 21 does not overheat. Therefore, the characteristics and reliability of the first capacitor 21 can be ensured.

[0061] like Figure 3As shown in (B), if the capacitance C1 of each of the second capacitor 22 and the third capacitor 23 is less than 0.047 μF, the neutral point voltage cannot be sufficiently smoothed, and the noise reduction effect generated by the motor 2 is relatively low. Furthermore, if the capacitance C1 of each capacitor is greater than 0.33 μF, the neutral point voltage is excessively smoothed, which significantly degrades the rotational characteristics of the motor 2. This makes it difficult to fully utilize the performance of the motor 2. Therefore, in this embodiment, the capacitance C1 of each of the second capacitor 22 and the third capacitor 23 is 0.1 μF, satisfying the condition 0.047 μF ≤ C1 ≤ 0.33 μF. This allows the noise generated by the motor 2 to be suppressed without degrading the rotational characteristics of the motor 2.

[0062] like Figure 3 As shown in (C), when the capacitance C3 of the fifth capacitor 25 is greater than 0.1 μF, noise generated by the FG output line 16 can be eliminated, but the output waveform of the speed signal tends to be blunted. Consequently, the external device cannot accurately detect the speed signal of the motor 2, making it difficult to control the motor 2 to the desired speed. Therefore, in this embodiment, the capacitance C3 of the fifth capacitor 25 is 0.047 μF, satisfying C3 ≤ 0.1 μF. This allows noise generated by the FG output line 16 to be eliminated, while also enabling the motor 2 to be controlled to the desired speed.

[0063] Since the motor 2 of this embodiment includes the motor control unit 10, it is possible to suppress the noise generated by the motor 2. Therefore, when the motor 2 of this embodiment is used in the pump device 1, the noise generated by the pump device 1 is suppressed, and precision equipment used around the pump device 1 is less likely to be affected by the noise. Furthermore, while the above embodiment describes the case where the motor 2 is used in the pump device 1, the motor 2 can be used in various applications.

Claims

1. A motor control unit for controlling a motor having three-phase coils, characterized in that: have: a motor control unit configured to control the rotation of the motor using a control signal; an inverter for applying a driving voltage supplied from a driving power supply to the three-phase coil in response to an output signal from the motor control unit; a driving voltage line, the driving voltage line supplying the driving voltage to the inverter; a common line electrically connected to a neutral point of the three-phase coil; an inductor, the inductor being electrically connected in series with the driving voltage line; a first capacitor electrically connected between a portion of the driving voltage line between the inverter and the inductor and ground; a second capacitor electrically connected between a portion of the driving voltage line closer to the input side than the first capacitor and ground; as well as a third capacitor electrically connected between the second capacitor and ground, The common line is electrically connected between the second capacitor and the third capacitor.

2. The motor control unit according to claim 1, characterized in that: If the capacitance of each of the second capacitor and the third capacitor is C1, the following conditional expression is satisfied: 0.047μF≤C1≤0.33μF.

3. The motor control unit according to claim 1 or 2, characterized in that: The second capacitor is electrically connected between a portion of the driving voltage line that is closer to the input side than the inductor and the ground.

4. The motor control unit according to any one of claims 1 to 3, characterized in that: If the electrostatic capacitance of the first capacitor is C2, the following conditional expression is satisfied: 100μF≤C2.

5. The motor control unit according to any one of claims 1 to 4, characterized in that: have: a control signal line for inputting the control signal to the motor control unit; and A fourth capacitor is electrically connected between the control signal line and ground.

6. The motor control unit according to claim 5, characterized in that: have: a ferrite bead electrically connected in series with the control signal line at a portion of the control signal line closer to the input side than the fourth capacitor; as well as A sixth capacitor is electrically connected between a portion of the control signal line that is closer to the input side than the ferrite bead and the ground.

7. The motor control unit according to any one of claims 1 to 6, characterized in that: have: an FG output line for transmitting a speed signal corresponding to the speed of the motor to an external device; and A fifth capacitor is electrically connected between the FG output line and ground.

8. The motor control unit according to claim 7, characterized in that: If the electrostatic capacitance of the fifth capacitor is C3, the following conditional expression is satisfied: C3≤0.1μF.

9. An electric motor comprising: a rotor capable of rotating about a central axis; A stator having a three-phase coil; And the motor control unit according to any one of claims 1 to 8.

10. A pump device, characterized in that: have: The electric motor according to claim 9; an impeller fixed to the rotor; and A casing that houses the impeller and divides the pump chamber.

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