Electric motor operating device

Abstract

A motor drive device according to the present invention comprises: an inverter that is electrically connected to a motor which has an air bearing; and an inverter control unit that provides the inverter with a PWM control signal on the basis of a pulse width modulation method for controlling an operation of the inverter. The inverter control unit outputs, to the inverter, a PWM control signal that includes a carrier wave which is set at a pre-levitation frequency when the air bearing is not in a levitation rotation speed range, or outputs, to the inverter, a PWM control signal that includes a carrier wave which is set at a post-levitation frequency when the air bearing is in the levitation rotation speed range. The pre-levitation frequency is lower than the post-levitation frequency.

Description

[Technical Field]

[0001] The present disclosure relates to electric motor operating devices. [Background technology]

[0002] Patent Document 1 discloses a technique related to a motor, which is an electric motor. The motor in Patent Document 1 has a thrust bearing made up of a support and a thrust magnet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-225079 Summary of the Invention [Problem to be solved by the invention]

[0004] An electric motor receives power from an external device. The electric motor then supplies the generated power to the external device. Inside the electric motor, a parasitic circuit may occur between the multiple components that make up the motor. If an unintended voltage occurs in the parasitic circuit, an unintended current will flow through the parasitic circuit. If an unintended current flows between the multiple components that make up the electric motor, the components that make up the motor will deteriorate.

[0005] The present disclosure describes an electric motor operating device that inhibits deterioration of components that make up the electric motor. [Means for solving the problem]

[0006] An electric motor operating device according to one embodiment of the present disclosure includes a power conversion unit electrically connected to an electric motor having a fluid dynamic bearing and operating based on a pulse control system, and a control unit that provides the power conversion unit with a control signal that controls the operation of the power conversion unit. The control unit outputs a control signal including a carrier wave with a first frequency to the power conversion unit when the fluid dynamic bearing is not in a floating support state, and outputs a control signal including a carrier wave with a second frequency to the power conversion unit when the fluid dynamic bearing is in a floating support state. The first frequency is lower than the second frequency.

[0007] The electric motor operating device sets the frequency of the carrier wave constituting the control signal given to the power conversion unit when the fluid bearing is not in a floating support state to be lower than the frequency of the carrier wave constituting the control signal given to the power conversion unit when the fluid bearing is in a floating support state. As a result, the frequency of axial currents occurring between the fluid bearing and the rotating shaft supported by the fluid bearing is reduced. Therefore, deterioration of parts caused by axial currents can be suppressed.

[0008] The control unit of the electric motor operating device may include a first calculation unit that sets a modulation factor of the control signal, a second calculation unit that sets a frequency of the carrier wave, and a third calculation unit that obtains the control signal using the modulation factor set by the first calculation unit and the frequency of the carrier wave set by the second calculation unit. The control unit can provide the power conversion unit with a control signal that can suppress deterioration of parts caused by axial current.

[0009] The second calculation unit of the electric motor operating device may set the frequency of the carrier wave to either a first frequency or a second frequency using information related to the rotation speed of the rotating shaft of the electric motor supported by the fluid bearing. Whether the fluid bearing is in a floating support state is related to the rotation speed. Therefore, the second calculation unit can use the rotation speed of the rotating shaft to set a frequency of the carrier wave that can suppress deterioration of components caused by axial current.

[0010] The second calculation unit of the electric motor operating device may set the frequency of the carrier wave to a first frequency when the rotation speed is in a non-floatation rotation speed range below a predetermined floatation rotation speed, and when it is in a margin rotation speed range below the margin rotation speed but equal to or greater than the floatation rotation speed. The second calculation unit may set the frequency of the carrier wave to a second frequency when the rotation speed is in a floatation rotation speed range equal to or greater than the margin rotation speed. The second calculation unit makes it possible to set a carrier wave frequency that can suppress deterioration of components caused by axial currents, even while the hydrodynamic bearing is transitioning from a state that is not in a floatation support state to a floatation support state.

[0011] The second calculation unit of the electric motor operating device may set the first frequency to a first constant value not based on the rotation speed when the rotation speed is in the non-floating rotation speed range and the margin rotation speed range. The second calculation unit may set the second frequency to a second constant value not based on the rotation speed when the rotation speed is in the floating rotation speed range. The first constant value may be smaller than the second constant value. The second calculation unit can easily set the frequency of the carrier wave.

[0012] The second calculation unit of the electric motor operating device may set the first frequency to a constant value not based on the rotation speed when the rotation speed is in the non-levitation rotation speed range and the margin rotation speed range. The second calculation unit may set the second frequency to a value that increases as the rotation speed increases, starting from the first frequency, when the rotation speed is in the levitation rotation speed range. The second calculation unit can set the frequency of the carrier wave according to the rotation speed when in the levitation support state.

[0013] The second calculation unit of the electric motor operating device may set the first frequency to a constant value not based on the rotation speed when the rotation speed is in the non-floating rotation speed range and the margin rotation speed range. The second calculation unit may set the second frequency to a value that starts at a value higher than the first frequency and increases as the rotation speed increases when the rotation speed is in the levitation rotation speed range. The second calculation unit can set the frequency of the carrier wave according to the rotation speed when in the levitation support state.

[0014] The second calculation unit of the electric motor operating device may set the first frequency to a constant value not based on the rotational speed when the rotational speed is in the non-floating rotational speed range and the margin rotational speed range. When the rotational speed is in the floating rotational speed range, the second calculation unit may set at least a first floating rotational speed range and a second floating rotational speed range having a rotational speed higher than the first floating rotational speed range. When the rotational speed is in the first floating rotational speed range, the second calculation unit may set the second frequency to a first constant value higher than the first frequency and not based on the rotational speed. When the rotational speed is in the second floating rotational speed range, the second calculation unit may set the second frequency to a second constant value higher than the first constant value and not based on the rotational speed. The second calculation unit can easily set the frequency of the carrier wave when the hydrodynamic bearing is in a floating support state.

[0015] The second calculation unit of the electric motor operating device may set the first frequency to a constant value not based on the rotational speed when the rotational speed is in the non-floating rotational speed range and the margin rotational speed range. When the rotational speed is in the floating rotational speed range, the second calculation unit may set at least a first floating rotational speed range and a second floating rotational speed range that is higher than the first floating rotational speed range. When the rotational speed is in the first floating rotational speed range, the second calculation unit may set the second frequency to a first constant value that is higher than the first frequency and is not based on the rotational speed. When the rotational speed is in the second floating rotational speed range, the second calculation unit may set the second frequency to a value that starts at the first constant value and increases as the rotational speed increases. When the hydrodynamic bearing is in a floating support state, the second calculation unit can set the frequency of the carrier wave according to the rotational speed.

[0016] The second calculation unit of the electric motor operating device may set the first frequency to a value that increases as the rotation speed increases when the rotation speed is in the non-floating rotation speed range and the margin rotation speed range. The second calculation unit may set the second frequency to a value that increases as the rotation speed increases, starting from the first frequency, when the rotation speed is in the floating rotation speed range. The second calculation unit can set the frequency of the carrier wave according to the rotation speed when the hydrodynamic bearing is not in a floating support state. The second calculation unit can also set the frequency of the carrier wave according to the rotation speed when the hydrodynamic bearing is in a floating support state.

[0017] The control unit of the electric motor operating device may set the frequency of the carrier wave to either a first frequency or a second frequency using information related to the rotation speed of the rotating shaft of the electric motor supported by the fluid dynamic bearing and the relationship between the rotation speed and the frequency of the carrier wave. The control unit may acquire information defined by a non-floating rotation speed range defined by an upper limit non-floating rotation speed (Nr) and a floating rotation speed range defined by an upper limit floating rotation speed (Nm). The relationship between the rotation speed and the frequency of the carrier wave may include a non-floating ratio ((fswb-fswc) / Nr) defined by the difference (fswb-fswc) between the maximum non-floating frequency (fswb) of the carrier wave when not in a floating support state and the minimum non-floating frequency (fswc) of the carrier wave when not in a floating support state, and a predetermined upper limit non-floating rotation speed (Nr), and a floating ratio (fsw1 / Nm) defined by the maximum floating frequency (fsw1) of the carrier wave when in a floating support state and the upper limit floating rotation speed (Nm) associated with the maximum floating frequency (fsw1), and may satisfy the condition that the floating ratio (fsw1 / Nm) is greater than the non-floating ratio ((fswb-fswc) / Nr).

[0018] This control unit can set a frequency of the carrier wave that can suppress deterioration of parts caused by axial current.

[0019] The control unit of the electric motor operating device may set the frequency of the carrier wave to either a first frequency or a second frequency, using information on the rotation speed of the rotating shaft of the electric motor supported by the hydrodynamic bearing and the relationship between the rotation speed and the frequency of the carrier wave. The relationship between the rotation speed and the frequency of the carrier wave may be determined by an upper non-floating rotation speed (Nr) indicating the upper limit of the rotation speed (N) of the rotating shaft when the hydrodynamic bearing is not in a floating support state, a lower non-floating rotation speed (Ns) indicating the lower limit of the rotation speed (N) of the rotating shaft when the hydrodynamic bearing is not in a floating support state, the relationship between the rotation speed (N) of the rotating shaft when the hydrodynamic bearing is not in a floating support state and the frequency of the carrier wave corresponding to the rotation speed (N) of the rotating shaft expressed as a function (f1(N)) with the rotation speed (N) of the rotating shaft as an independent variable and the frequency of the carrier wave as a dependent variable, and a function (f1(N)) indicating the relationship between the rotation speed (N) of the rotating shaft when the hydrodynamic bearing is not in a floating support state and the frequency of the carrier wave corresponding to the rotation speed (N) of the rotating shaft expressed as a function (f1(N)) with the rotation speed (N) of the rotating shaft as an independent variable and the frequency of the carrier wave as a dependent variable. The relationship between the rotation speed (N) of the rotating shaft when the fluid bearing is in a floating support state and the frequency of the carrier wave corresponding to the rotation speed (N) of the rotating shaft may satisfy the condition expressed by equation (1), which includes an upper limit levitation rotation speed (Nm) indicating the upper limit of the rotation speed (N) of the rotating shaft when the fluid bearing is in a floating support state, a lower limit levitation rotation speed (Nc) indicating the lower limit of the rotation speed (N) of the rotating shaft when the fluid bearing is in a floating support state, and a function (f2(N)) indicating the rotation speed (N) of the rotating shaft as an independent variable and the frequency of the carrier wave as a dependent variable.

number

[0020] The control unit can set a frequency of the carrier wave that can suppress deterioration of components caused by the axial current.

[0021] The control unit of the electric motor operating device may include a signal acquisition unit that receives a signal indicating whether the rotating shaft of the electric motor supported by the fluid bearing has floated. The second calculation unit may set the frequency of the carrier wave using the signal acquired by the signal acquisition unit. The control unit can set the frequency of the carrier wave that can suppress deterioration of parts caused by axial current without using the rotation speed of the rotating shaft.

[0022] Another aspect of the present disclosure provides an electric motor-operated device that is electrically connected to an electric motor having a fluid dynamic bearing and includes a power conversion unit that operates based on a pulse control method. The power conversion unit outputs a first output voltage pulse when the fluid dynamic bearing is not in a floating support state. The power conversion unit outputs a second output voltage pulse when the fluid dynamic bearing is in a floating support state. The frequency of the first output voltage pulse is lower than the frequency of the second output voltage pulse. The electric motor-operated device can suppress deterioration of components caused by axial current.

[0023] In another embodiment of the motor operating device, the time average value obtained by dividing the value obtained by integrating the frequency of the second output voltage pulse with respect to time by a reference time may be smaller than the time average value obtained by dividing the value obtained by integrating the frequency of the first output voltage pulse with respect to time by the reference time. This configuration also makes it possible to suppress deterioration of parts caused by axial current. [Effects of the Invention]

[0024] According to the electric motor operating device of the present disclosure, deterioration of the components that make up the electric motor can be suppressed. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a functional block diagram of a system including an electric motor operating device according to a first embodiment. [Figure 2] FIG. 2 is a diagram for explaining the operation of the switching frequency calculation unit. [Figure 3] Fig. 3(a) is a diagram explaining the levitation support state. Fig. 3(b) is a diagram explaining the touchdown state. Fig. 3(c) is a diagram explaining the axial current generated in the levitation support state. Fig. 3(d) is a diagram explaining the axial current generated in the touchdown state. [Figure 4] 4(a) and 4(b) are diagrams showing output voltage pulses in a non-floating state and a floating state, respectively. [Figure 5]Fig. 5(a) is a diagram for explaining a first modified example in the operation of the switching frequency calculation unit, and Fig. 5(b) is a diagram for explaining a second modified example in the operation of the switching frequency calculation unit. [Figure 6] Fig. 6(a) is a diagram for explaining a third modified example in the operation of the switching frequency calculation unit, and Fig. 6(b) is a diagram for explaining a fourth modified example in the operation of the switching frequency calculation unit. [Figure 7] FIG. 7 is a diagram for explaining a fifth modified example of the operation of the switching frequency calculation unit. [Figure 8] FIG. 8 is a diagram for explaining a sixth modified example of the operation of the switching frequency calculation unit. [Figure 9] FIG. 9 is a functional block diagram of a system including an electric motor operating device according to the seventh modified example. [Figure 10] FIG. 10 is a diagram for explaining an eighth modified example of the operation of the switching frequency calculation unit. [Figure 11] FIG. 11 is a diagram for explaining a ninth modification of the operation of the switching frequency calculation unit. DETAILED DESCRIPTION OF THE INVENTION

[0026] The electric motor operating device of the present disclosure will be described in detail below with reference to the accompanying drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted.

[0027] The electric motor operating device of the embodiment is used to operate an electric motor. The electric motor may be a motor that is driven by receiving electric power. The electric motor may also be a generator that receives energy from an external source and generates electric power. In the following explanation, the electric motor is assumed to be a motor 2 as shown in FIG. 1. The electric motor operating device is a motor driving device 1 that converts electric power received from a DC power supply 3 into a form of electric power required by the motor 2. The motor driving device 1 provides the converted electric power to the motor 2. The electric power received by the motor driving device 1 may be DC or AC.

[0028] The motor 2 includes a rotor 21 including magnets and a stator 22 including coils. The motor drive device 1 supplies three-phase AC power to the coils of the stator 22. As a result, the rotor 21 rotates due to the interaction between the magnetic field generated by the coils of the stator 22 that receive the three-phase AC and the magnetic field of the magnets in the rotor 21.

[0029] A rotating shaft 23 is connected to the rotor 21. A pair of air bearings 24 is provided on both ends of the rotating shaft 23. When the rotating shaft 23 rotates at a rotation speed higher than a predetermined rotation speed, the air bearings 24 rotatably support the rotating shaft 23 without contact. The air bearing 24 is a type of fluid bearing. The air bearing 24 supports a load acting on the rotating shaft 23 due to air pressure caused by air entrained inside the bearing (see FIG. 3(a)).

[0030] When the rotating shaft 23 is in a rotating state, the outer peripheral surface 231 of the rotating shaft 23 is not in contact with the inner peripheral surface 242 of the bearing ring 241. An air layer 243 exists between the outer peripheral surface 231 of the rotating shaft 23 and the inner peripheral surface 242 of the bearing ring 241.

[0031] The air layer 243 formed on the vertically lower side is generated by air being sucked in as the rotating shaft 23 rotates. When the rotating shaft 23 is not rotating, the outer peripheral surface 231 of the rotating shaft 23 contacts the inner peripheral surface 242 of the bearing ring 241 (see FIG. 3(b)). The state in which the outer peripheral surface 231 of the rotating shaft 23 contacts the inner peripheral surface 242 of the bearing ring 241 is called a touchdown state S1.

[0032] Referring again to Figure 1, the motor driving device 1 has an inverter 11 (power conversion unit) and an inverter control unit 12 (control unit).

[0033] The inverter 11 includes a circuit having a plurality of switch elements. By switching the plurality of switch elements ON and OFF, the inverter 11 converts DC power into three-phase AC power. The inverter 11 employs a pulse control method. For example, the inverter 11 may employ a pulse width modulation (PWM) method. The inverter 11 may employ a pulse amplitude modulation (PAM) method. Hereinafter, the inverter 11 will be described as employing a pulse width modulation (PWM) method. A known power conversion circuit can be used as the power conversion circuit provided in the inverter 11. Therefore, a detailed description of the inverter 11 will be omitted.

[0034] The inverter control unit 12 is physically a computer. The inverter control unit 12 receives a control command value φ1 provided from the outside. The inverter control unit 12 receives a sensor detection value φ11 from the inverter 11. The inverter control unit 12 generates a PWM control signal φ123 for the inverter 11 using the control command value φ1 and the sensor detection value φ11. For example, the control target of the inverter 11 may be the rotation speed of the motor 2, the torque of the motor 2, or the actuator position.

[0035] The PWM control signal φ123 is a signal based on pulse width modulation and is generated by a carrier wave component defined by a predetermined frequency and a modulation component derived from the control command value φ1.

[0036] The inverter control unit 12 includes, as functional components, a modulation factor calculation unit 121 (first calculation unit), a switching frequency calculation unit 122 (second calculation unit), and a PWM control signal calculation unit 123 (third calculation unit). The functional components constituting the inverter control unit 12 are realized by executing a predetermined program in the CPU of the computer. The inverter control unit 12 may include other functional components not shown in FIG. 1.

[0037] The modulation factor calculation unit 121 obtains the modulation factor φ121 through calculation. The modulation factor calculation unit 121 receives a control command value φ1 from outside the motor drive device 1. The control command value φ1 may be, for example, a target value for the rotation speed of the motor 2. The modulation factor calculation unit 121 receives a sensor detection value φ11 from the inverter 11. The modulation factor calculation unit 121 calculates the modulation factor φ121 for PWM control using the control command value φ1 and the sensor detection value φ11. The modulation factor calculation unit 121 passes the modulation factor φ121 to the PWM control signal calculation unit 123. The modulation factor calculation unit 121 passes rotation speed information φ2 indicating the rotation speed of the motor 2 to the switching frequency calculation unit 122.

[0038] The switching frequency calculation unit 122 sets a switching frequency φ122 for PWM control. The switching frequency φ122 is the frequency of a carrier wave in PWM control. The switching frequency calculation unit 122 sets the switching frequency φ122 using rotation speed information φ2 indicating the rotation speed of the motor 2 received from the modulation factor calculation unit 121. The switching frequency calculation unit 122 may obtain the rotation speed information φ2 directly from the outside without going through the modulation factor calculation unit 121. The specific details of setting the switching frequency φ122 using the rotation speed information φ2 will be described later. The switching frequency calculation unit 122 passes the switching frequency φ122 to the PWM control signal calculation unit 123.

[0039] The PWM control signal calculation unit 123 obtains a PWM control signal φ123. The PWM control signal calculation unit 123 receives the modulation factor φ121 from the modulation factor calculation unit 121. The PWM control signal calculation unit 123 receives the switching frequency φ122 from the switching frequency calculation unit 122. The PWM control signal calculation unit 123 obtains the PWM control signal φ123 using the modulation factor φ121 and the switching frequency φ122. The PWM control signal calculation unit 123 passes the PWM control signal φ123 to the inverter 11.

[0040] The following is a detailed description of the switching frequency calculation unit 122. The calculation here does not necessarily have to involve calculations such as the four basic arithmetic operations.

[0041] The switching frequency calculation unit 122 sets the switching frequency φ122 using information φ4 indicating the relationship between the rotation speed and the switching frequency. The information φ4 indicating the relationship between the rotation speed and the switching frequency can take various forms. For example, the information φ4 indicating the relationship between the rotation speed and the switching frequency may be a function with the rotation speed as an independent variable and the switching frequency as a dependent variable. The information φ4 indicating the relationship between the rotation speed and the switching frequency may be a table in which the rotation speed is associated with the switching frequency corresponding to that rotation speed. The information φ4 indicating the relationship between the rotation speed and the switching frequency may be a rotation speed-frequency map M1 as shown in FIG. 2. The vertical axis of the rotation speed-frequency map M1 represents the switching frequency φ122. The horizontal axis represents the rotation speed N. The rotation speed N includes a non-floating rotation speed region N1, a margin rotation speed region N2, and a floating rotation speed region N3. The information φ4 indicating the relationship between the rotation speed and the switching frequency is recorded in the storage device 13 included in the inverter control unit 12, and the switching frequency calculation unit 122 may read out the information φ4 indicating the relationship between the rotation speed and the switching frequency from the storage device 13 as necessary. The information φ4 indicating the relationship between the rotation speed and the switching frequency may be provided from an external device 4 separate from the motor drive device 1.

[0042] In the following description, it is assumed that the switching frequency calculation unit 122 sets the switching frequency φ122 using the rotation speed-frequency map M1.

[0043] The non-floating rotation speed region N1 is a range in which the rotation speed N ranges from a lower limit non-floating rotation speed Ns (e.g., zero) to less than a floating rotation speed Nr (an upper limit non-floating rotation speed). The non-floating rotation speed region N1 corresponds to the touchdown state S1 shown in FIG. 3(b). In this case, the rotating shaft 23 rotates while contacting the inner circumferential surface 242 of the bearing ring 241. The floating rotation speed Nr is a preset value. The floating rotation speed Nr refers to the rotation speed N at which the rotating shaft 23 rotates in a floating state. Specifically, the floating rotation speed Nr may refer to the rotation speed N at which the floating support state S2 shown in FIG. 3(a) is reached. The floating rotation speed Nr may refer to the rotation speed N at which the transition from the touchdown state S1 shown in FIG. 3(b) to the floating support state S2 shown in FIG. 3(a) begins. The floating rotation speed Nr may be obtained by calculation. The levitation rotation speed Nr may be obtained by experiment, measurement during operation, or calculation.

[0044] The margin rotation speed region N2 is a range equal to or greater than the floating rotation speed Nr but less than the margin rotation speed Nc (lower limit floating rotation speed). When the margin rotation speed region N2 is in the margin rotation speed region N2, the rotating shaft 23 may be in the floating support state S2 shown in FIG. 3(a), or may be in a transition state from the touchdown state S1 shown in FIG. 3(b) to the floating support state S2 shown in FIG. 3(a). The margin rotation speed Nc is a margin added to the floating rotation speed Nr. The floating rotation speed Nr is a value indicating that the rotating shaft 23 has floated. However, "floating" involves a certain degree of uncertainty. The margin rotation speed Nc is set to a value greater than the floating rotation speed Nr. When the rotation speed N is equal to or greater than the margin rotation speed Nc, the rotating shaft 23 is in the floating support state S2 shown in FIG. 3(b).

[0045] The floating rotation speed range N3 is a range equal to or greater than the margin rotation speed Nc. In the floating rotation speed range N3, the floating support state S2 shown in FIG.

[0046] The switching frequency calculation unit 122 sets a pre-flight frequency fswa and a post-flight frequency fsw0. The pre-flight frequency fswa is lower than the post-flight frequency fsw0. The pre-flight frequency fswa is a constant value that is not based on the rotation speed N. The post-flight frequency fsw0 is also a constant value that is not based on the rotation speed N. The pre-flight frequency fswa and the post-flight frequency fsw0 may each be determined from the perspective of control stability according to the rotation speed N.

[0047] The switching frequency calculation unit 122 sets the pre-flight frequency fswa as the switching frequency φ122 when the rotation speed N indicated by the rotation speed information φ2 is in the non-flighting rotation speed region N1. Because the pre-flighting frequency fswa is a constant value that is not based on the rotation speed, when the rotation speed N is in the non-flighting rotation speed region N1, the switching frequency φ122 is always a constant value (pre-flighting frequency fswa). The switching frequency calculation unit 122 also sets the pre-flighting frequency fswa as the switching frequency φ122 when the rotation speed N indicated by the rotation speed information φ2 is in the margin rotation speed region N2. The switching frequency calculation unit 122 sets the post-flighting frequency fsw0 as the switching frequency φ122 when the rotation speed N indicated by the rotation speed information φ2 is in the floatation rotation speed region N3. Since the post-floating frequency fsw0 is also a constant value that is not based on the rotation speed, even when the rotation speed N is in the floating rotation speed range N3, the switching frequency φ122 is always a constant value (post-floating frequency fsw0).

[0048] The number of switching frequencies associated with one rotation speed N is not limited to one. For example, two switching frequencies can be associated with one rotation speed N. For example, switching frequencies fswa and fsw0 can be associated with rotation speed Nc. When transitioning from a non-floating state to a floating state, switching frequency fsw0 is used for rotation speed Nc. When transitioning from a floating state to a non-floating state, switching frequency fswa is used for rotation speed Nc.

[0049] 2, for example, when the rotation speed is N1a included in the non-floating rotation speed range N1, the switching frequency calculation unit 122 selects the switching frequency fsw(N1a) corresponding to the rotation speed N1a. The PWM control signal calculation unit 123 generates a PWM control signal φ123 based on the switching frequency fsw(N1a) and outputs the PWM control signal φ123 to the inverter 11.

[0050] In response to the PWM control signal φ123, the inverter 11 outputs the phase voltages shown in Fig. 4(a). The frequency of the output voltage pulse P1 is based on the switching frequency fsw (N1a). The fundamental wave W1 of the output voltage of the inverter 11 is based on the rotation speed N1a.

[0051] In the rotation speed-frequency map M1 shown in Fig. 2, for example, when the rotation speed is N3a, which is included in the levitation rotation speed range N3, the inverter 11 outputs the phase voltage shown in Fig. 4(b). The period of the output voltage pulse P2 is based on the switching frequency fsw(N2a). The fundamental wave W2 of the output voltage of the inverter 11 is based on the rotation speed N2a.

[0052] The switching frequency fsw(N3a) is higher than the switching frequency fsw(N1a). Therefore, the frequency of the output voltage pulse P2 in the levitated state is also higher than the frequency of the output voltage pulse P1 in the non-levitated state.

[0053] The rotation speed N3a included in the levitation rotation speed range N3 is higher than a certain rotation speed N1a included in the non-levitation rotation speed range N1. Therefore, the frequency of the fundamental wave W2 of the inverter output voltage in the levitation state is also higher than the frequency of the fundamental wave W1 of the inverter output voltage in the non-levitation state.

[0054] The following describes the effects of the above-described motor drive device 1. Specifically, this section explains why switching frequency calculation unit 122 sets switching frequency φ122 in accordance with the state of air bearing 24. This section also explains why such setting of switching frequency φ122 suppresses deterioration of air bearing 24.

[0055] In the floating support state S2 shown in Fig. 3(c), an air layer 243 is formed between the rotating shaft 23 and the bearing ring 241. As a result, the distance from the outer peripheral surface 231 of the rotating shaft 23 to the inner peripheral surface 242 of the bearing ring 241 is a state in which there is sufficient electrical separation. The rotating shaft 23 and the bearing ring 241 form a parasitic capacitance to the ground. A state in which there is sufficient electrical separation means that the parasitic capacitance to the ground is sufficiently small.

[0056] On the other hand, in the touchdown state S1 (not in the floating support state) shown in FIG. 3(d), the rotating shaft 23 contacts the bearing ring 241. No air layer 243 is formed. The rotating shaft 23 contacts the bearing ring 241 via a surface coating layer formed on the inner peripheral surface 242 of the bearing ring 241. As a result, the distance between the outer peripheral surface 231 of the rotating shaft 23 and the inner peripheral surface 242 of the bearing ring 241 is not sufficiently electrically separated. The parasitic capacitance to the ground in the touchdown state S1 is greater than the parasitic capacitance to the ground in the floating support state S2.

[0057] When the motor 2 is driven by switching the inverter 11, a shaft voltage is induced. As a result, a shaft current C is generated according to the ground impedance. The shaft current C flows through a parasitic circuit including the ground parasitic capacitance formed by the rotating shaft 23 and the bearing ring 241. The shaft current C in the touchdown state S1, where the ground parasitic capacitance is large, is larger than the shaft current C in the levitation support state S2, where the ground parasitic capacitance is small. Excessive shaft current C may damage the air bearing 24. Excessive shaft current C may also deteriorate the air bearing 24.

[0058] After careful consideration, the inventors have come up with the idea of ​​reducing the frequency with which axial current C is generated in touchdown state S1 in order to reduce the stress on air bearing 24. The frequency with which axial current C is generated depends on switching frequency φ122. The switching frequency φ122 in touchdown state S1, in which excessive axial current C is likely to be generated, is set lower than the switching frequency φ122 during normal operation (levitation support state S2). As a result, the frequency with which axial current C is generated in touchdown state S1 is reduced. As a result, deterioration of air bearing 24 that constitutes motor 2 can be suppressed.

[0059] The motor drive device 1 includes an inverter 11 electrically connected to a motor 2 having an air bearing 24, and an inverter control unit 12 that supplies the inverter 11 with a PWM control signal φ123 based on a pulse control method to control the operation of the inverter 11. The inverter control unit 12 outputs the PWM control signal φ123 including a carrier wave with a first frequency to the inverter 11 when the air bearing 24 is in a touchdown state S1 that is not the floating support state S2. The inverter control unit 12 outputs the PWM control signal φ123 including a carrier wave with a second frequency to the inverter 11 when the air bearing 24 is in the floating support state S2. The first frequency is lower than the second frequency. The first frequency and the second frequency may be predetermined constant values. The first frequency and the second frequency may be a set of multiple discrete frequencies. The first frequency and the second frequency may be a continuous frequency band. The first frequency and the second frequency may be a set of one or more continuous frequency bands and one or more discrete values.

[0060] Motor drive device 1 sets the frequency of the carrier wave constituting PWM control signal φ123 given to inverter 11 when air bearing 24 is in touchdown state S1 to be lower than the frequency of the carrier wave constituting PWM control signal φ123 given to inverter 11 when air bearing 24 is in floating support state S2. As a result, the frequency with which axial current C is generated between air bearing 24 and rotating shaft 23 is reduced, thereby suppressing deterioration of air bearing 24 due to axial current C. This makes it possible to improve the reliability and lifespan of motor 2 that employs air bearing 24.

[0061] Inverter control unit 12 of motor drive device 1 includes a modulation factor calculation unit 121 that sets a modulation factor φ121 of a PWM control signal φ123, a switching frequency calculation unit 122 that sets the frequency of a carrier wave, and a PWM control signal calculation unit 123 that obtains the PWM control signal φ123 using the modulation factor φ121 set by modulation factor calculation unit 121 and the frequency of the carrier wave set by switching frequency calculation unit 122. Inverter control unit 12 can provide inverter 11 with a PWM control signal φ123 that can suppress deterioration of parts caused by axial current C.

[0062] Switching frequency calculation unit 122 of motor drive device 1 sets the frequency of the carrier wave to either a first frequency or a second frequency, using information related to the rotation speed N of rotating shaft 23 of motor 2 supported by air bearing 24. Whether air bearing 24 is in the floating support state S2 is related to rotation speed N. Therefore, switching frequency calculation unit 122 can use rotation speed N of rotating shaft 23 to set a frequency of the carrier wave that can suppress deterioration of air bearing 24 caused by axial current C.

[0063] The switching frequency calculation unit 122 sets the frequency of the carrier wave to a first frequency when the rotation speed N is in a non-floating rotation speed range N1 that is less than a preset floating rotation speed Nr. The switching frequency calculation unit 122 sets the frequency of the carrier wave to the first frequency when the rotation speed N is less than a margin rotation speed Nc that is equal to or greater than the floating rotation speed Nr and is in a margin rotation speed range N2 that is equal to or greater than the floating rotation speed Nr. The switching frequency calculation unit 122 sets the frequency of the carrier wave to a second frequency when the rotation speed N is in a floating rotation speed range N3 that is equal to or greater than the margin rotation speed Nc. The switching frequency calculation unit 122 can set the frequency of the carrier wave that can suppress deterioration of the air bearing 24 due to the axial current C, even while the state of the air bearing 24 is transitioning from the touchdown state S1 to the floating support state S2.

[0064] When in the non-flight rotation speed range N1 and the margin rotation speed range N2, the switching frequency calculation unit 122 sets the first frequency to a pre-flight frequency fswa that is not based on the rotation speed N. When in the flight rotation speed range N3, the switching frequency calculation unit 122 sets the second frequency to a post-flight frequency fsw0 that is higher than the pre-flight frequency fswa that is not based on the rotation speed N. The switching frequency calculation unit 122 can easily set the frequency of the carrier wave.

[0065] <Modification> The motor operating device of the present disclosure is not limited to the above-described embodiment. For example, the operation of setting the switching frequency φ122 performed by the switching frequency calculation unit 122 is not limited to the operation shown in Fig. 2. First to sixth modified examples of the switching frequency calculation unit 122 will be described below.

[0066] <First Modification> Fig. 5(a) is a rotation speed-frequency map M2 for explaining a first modified example regarding the operation of the switching frequency calculation unit 122. As shown in Fig. 5(a), the frequency set when the rotation speed N is in the non-flight rotation speed region N1 and the margin rotation speed region N2 is a constant value (pre-flight frequency fswa) as in the embodiment. On the other hand, the frequency set when the rotation speed N is in the flight rotation speed region N3 is a proportional value that increases up to the maximum flight frequency fsw1 according to the rotation speed N.

[0067] The switching frequency calculation unit 122 of the first modified example sets the first frequency to a pre-flight frequency fswa that is not based on the rotation speed N when the rotation speed N is in the non-flight rotation speed range N1 and the margin rotation speed range N2. When the rotation speed N is in the flight rotation speed range N3, the switching frequency calculation unit 122 of the first modified example sets the second frequency to a value that increases from the pre-flight frequency fswa as a starting value up to the maximum flight frequency fsw1 as the rotation speed N increases. The switching frequency calculation unit 122 can set the frequency of the carrier wave according to the rotation speed N when in the float support state S2.

[0068] <Second Modification> FIG. 5(b) is a rotation speed-frequency map M3 for explaining a second modified example related to the operation of the switching frequency calculation unit 122. As shown in FIG. 5(b), the frequency set when the rotation speed N is in the non-floating rotation speed range N1 and in the margin state is a constant value (pre-floating frequency fswa) as in the embodiment. On the other hand, the frequency set when the rotation speed N is in the floating rotation speed range N3 is a proportional value that increases up to the maximum floating frequency fsw1 according to the rotation speed N. In the first modified example, the initial value of the second frequency was the pre-floating frequency fswa. In the second modified example, the initial value of the second frequency is the first post-floating frequency fsw2 that is greater than the pre-floating frequency fswa.

[0069] The switching frequency calculation unit 122 of the second modified example sets the first frequency to a constant value not based on the rotation speed N when the rotation speed N is in the non-floating rotation speed range N1 and the margin rotation speed range N2. When the rotation speed N is in the floating rotation speed range N3, the switching frequency calculation unit 122 sets the second frequency to a value that starts at a first post-floating frequency fsw2 that is higher than the pre-floating frequency fswa and increases up to the maximum floating frequency fsw1 as the rotation speed N increases. The switching frequency calculation unit 122 can set the frequency of the carrier wave according to the rotation speed N when in the floating support state S2.

[0070] <Third Modification> FIG. 6A illustrates a rotational speed-frequency map M4 for explaining a third modified example of the operation of the switching frequency calculation unit 122. As shown in FIG. 6A, the frequency set when the rotational speed N is in the non-floating rotational speed range N1 and the margin rotational speed range N2 is a constant value (pre-floating frequency fswa), as in the embodiment. Meanwhile, in the floating rotational speed range N3, the switching frequency calculation unit 122 sets the frequency to several ranges: a first floating rotational speed range N31, a second floating rotational speed range N32, and a third floating rotational speed range N33. The switching frequency calculation unit 122 sets the frequency so that the value increases stepwise for each rotational speed range. In the example illustrated in FIG. 6A, the switching frequency calculation unit 122 sets the first frequency to a first post-floating frequency fsw2 when the rotational speed N is in the first floating rotational speed range N31. The switching frequency calculation unit 122 sets the first frequency to the second post-floating frequency fsw2a when the rotation speed N is in the second floating rotation speed range N32, and to the maximum floating frequency fsw1 when the rotation speed N is in the third floating rotation speed range N33.

[0071] The switching frequency calculation unit 122 of the third modification sets the first frequency to a constant value not based on the rotation speed when the rotation speed N is in the non-floating rotation speed range N1 and the margin rotation speed range N2. When the rotation speed N is in the floating rotation speed range N3, the switching frequency calculation unit 122 sets at least a first floating rotation speed range N31, a second floating rotation speed range N32, and a third floating rotation speed range N33. When the rotation speed N is in the first floating rotation speed range N31, the switching frequency calculation unit 122 sets the second frequency to a first post-floating frequency fsw2 not based on the rotation speed. When the rotation speed N is in the second floating rotation speed range N32, the switching frequency calculation unit 122 sets the second frequency to a second post-floating frequency fsw2a not based on the rotation speed. When the rotation speed N is in the third levitation rotation speed range N33, the switching frequency calculation unit 122 sets the second frequency to the levitation maximum frequency fsw1 that is not based on the rotation speed. When the air bearing 24 is in the levitation support state S2, the switching frequency calculation unit 122 can simply set the frequency of the carrier wave.

[0072] <Fourth Modification> FIG. 6B shows a rotation speed-frequency map M5 for explaining a fourth modified example of the operation of the switching frequency calculation unit 122. As shown in FIG. 6B, the frequency set when the rotation speed N is in the non-floating rotation speed range N1 and the margin rotation speed range N2 is a constant value (pre-floating frequency fswa), as in the embodiment. When the rotation speed N is in the float rotation speed range N3 and in the first float rotation speed range N31, the switching frequency calculation unit 122 sets the second frequency to the first post-floating frequency fsw2, which is a constant value. When the rotation speed N is in the float rotation speed range N3 and in the second float rotation speed range N32, the switching frequency calculation unit 122 sets the second frequency to a value that increases up to the maximum float frequency fsw1 as the rotation speed N increases.

[0073] In the fourth modification, the switching frequency calculation unit 122 sets the first frequency to a constant value that is not based on the rotation speed when the rotation speed N is in the non-floating rotation speed range N1 and the margin rotation speed range N2. When the rotation speed N is in the floating rotation speed range N3, the switching frequency calculation unit 122 sets at least a first floating rotation speed range N31 and a second floating rotation speed range N32. When the rotation speed N is in the first floating rotation speed range N31, the switching frequency calculation unit 122 sets the second frequency to a first post-floating frequency fsw2 that is higher than the first frequency and is not based on the rotation speed. When the rotation speed N is in the second floating rotation speed range N32, the switching frequency calculation unit 122 sets the second frequency to a value that starts at the first post-floating frequency fsw2 and increases up to the floating maximum frequency fsw1 as the rotation speed N increases. Switching frequency calculation unit 122 can set the frequency of the carrier wave according to the rotation speed when air bearing 24 is in floating support state S2.

[0074] <Fifth Modification> Fig. 7 is a rotation speed-frequency map M6 for explaining a fifth modified example related to the operation of the switching frequency calculation unit 122. As shown in Fig. 7, when the rotation speed N is in the non-flighting rotation speed region N1 and the margin rotation speed region N2, the switching frequency calculation unit 122 sets the first frequency to a value that increases from the pre-flighting frequency fswc to the pre-flighting frequency fswb as the rotation speed N increases. When the rotation speed N is in the flighting rotation speed region N3, the switching frequency calculation unit 122 sets the second frequency to a value that increases from the pre-flighting frequency fswb to the maximum flighting frequency fsw1 as the rotation speed N increases.

[0075] In the fifth modified example, when the rotation speed N is in the non-floating rotation speed range N1 or the margin rotation speed range N2, the switching frequency calculation unit 122 sets the first frequency to a value that increases as the rotation speed N increases. When the rotation speed N is in the floating rotation speed range N3, the switching frequency calculation unit 122 sets the second frequency to a value that increases from the pre-floating frequency fswb as a starting value to the maximum floating frequency fsw1 as the rotation speed N increases. The switching frequency calculation unit 122 can set the frequency of the carrier wave according to the rotation speed N when the air bearing 24 is not in the floating support state S2. The switching frequency calculation unit 122 can set the frequency of the carrier wave according to the rotation speed N when the air bearing 24 is in the floating support state S2.

[0076] <Sixth Modification> The pre-floating frequency fswa and the post-floating frequency fsw0 can also be defined from another perspective. A first condition, defined from another perspective, includes a floating ratio R1 (fsw1 / Nm) between the maximum floating frequency fsw1 of the carrier wave when in the floating support state S2 and the maximum floating rotation speed Nm (upper limit floating rotation speed) associated with the maximum floating frequency fsw1. The floating ratio R1 (fsw1 / Nm) corresponds to graph G7a of the rotation speed-frequency map M7 shown in FIG. 8. The first condition includes a non-floating ratio R2 ((fswb-fswc) / Nr) between the difference (fswb-fswc) between the maximum non-floating frequency fswb of the carrier wave when not in the floating support state S2 and the minimum non-floating frequency fswc of the carrier wave when not in the floating support state S2 and a preset floating rotation speed Nr. The non-floating ratio R2 corresponds to graph G7b shown in FIG. 8. The floating ratio R1 (fsw1 / Nm) is greater than the non-floating ratio R2 ((fswb-fswc) / Nr).

[0077] The first condition may be a non-floating ratio R2A ((fswb-fswc) / Nc) of the difference (fswb-fswc) between the non-floating maximum frequency fswb and the non-floating minimum frequency fswc of the carrier wave when not in the floating support state S2, to the lower limit floating rotation speed (Nc). The lower limit floating rotation speed Nc may also be used to define the first condition. The floating ratio R1 (fsw1 / Nm) is greater than the non-floating ratio R2A ((fswb-fswc) / Nc).

[0078] The operation of the inverter control unit 12 in the sixth modified example also makes it possible to set the frequency of the carrier wave that can suppress deterioration of parts caused by the axial current C.

[0079] <Seventh Modification> A modified example from another perspective will now be described. In the above embodiment, the rotation speed information φ2 is used to determine whether the state of the rotating shaft 23 supported by the air bearing 24 is in the non-floating rotation speed region N1, the margin rotation speed region N2, or the floating rotation speed region N3, and the switching frequency φ122 is set according to which state.

[0080] 9, motor drive device 1A, which is a seventh modified example, uses information other than rotation speed information φ2 to determine the state of rotating shaft 23 supported by air bearing 24. For example, inverter control unit 12A of motor drive device 1A includes air bearing floating signal acquirer 124 (signal acquirer) that receives floating detection signal φ3 indicating that rotating shaft 23 has floated.

[0081] The air bearing floating signal acquirer 124 may receive a floating detection signal φ3 from a floating detection sensor 25 provided in the motor 2. The air bearing floating signal acquirer 124 may receive the floating detection signal φ3 from the inverter 11 as the sensor detection value φ11. When the air bearing floating detection signal φ3 is received, the air bearing floating signal acquirer 124 passes a signal φ124 indicating that the current is in the floating rotation speed range N3 to the switching frequency calculator 122. When the air bearing floating detection signal φ3 is not received, the air bearing floating signal acquirer 124 passes a signal φ124 indicating that the current is in the non-floating rotation speed range N1 or the margin rotation speed range N2 to the switching frequency calculator 122. The switching frequency calculator 122 sets the switching frequency φ122 to either the pre-floating frequency fswa or the post-floating frequency fsw0 in accordance with the graph shown in FIG. 2.

[0082] The switching frequency calculation unit 122 of the modified example may additionally receive rotation speed information φ2. When the rotation speed information φ2 is received, the second frequency can be set to a value that increases according to the rotation speed N in accordance with the graphs shown in Fig. 2 and Figs. 5 to 7.

[0083] Inverter control unit 12A of motor drive device 1A has air bearing levitation signal acquisition unit 124 that receives a signal indicating whether rotating shaft 23 of motor 2, which is supported by air bearing 24, has levitated. Switching frequency calculation unit 122 sets the frequency of the carrier wave using the signal acquired by air bearing levitation signal acquisition unit 124. Inverter control unit 12 can set the frequency of the carrier wave that can suppress deterioration of parts caused by axial current C, without using the rotation speed.

[0084] <Eighth Modification> The relationship between the rotation speed N and the switching frequency fsw of the carrier wave may be defined by equation (1). Equation (1) is a definition using the average of the switching frequency fws with respect to the rotation speed N.

[0085] The left side of equation (1) is the average of the switching frequency fws with respect to the rotation speed N when in a levitated state. The right side of equation (1) is the average of the switching frequency fws with respect to the rotation speed N when in a non-levitated state. For example, the average of the switching frequency fws with respect to the rotation speed when in a non-levitated state is the value obtained by dividing the area of ​​region Q1 surrounded by the X-axis, Y-axis, and line indicating the rotation speed Nr, and line L1 indicating the relationship between the rotation speed N and the switching frequency fsw, by the band (Nr-Ns) of the non-levitated rotation speed range N1, as shown in FIG.

[0086] Similarly, the average of the switching frequency fws for the rotation speed N when in the levitated state is the value obtained by dividing the area of ​​region Q2 by the band (Nm-Nc) of the levitation rotation speed range N3. The relationship between the rotation speed N and the switching frequency fsw of the carrier wave can be defined as follows: the average of the switching frequency fws for the rotation speed when in the non-levitated state is smaller than the average of the switching frequency fws for the rotation speed when in the levitated state.

number

[0087] <Ninth Variation> When starting the motor 2 that is stopped, the inverter 11 supplies an output voltage pulse P to the motor 2 under the control of the motor drive device 1. When the motor 2 receives the output voltage pulse P, the rotation speed of the rotating shaft 23 gradually increases. At this time, the rotating shaft 23 starts rotating from a touchdown state S1 in which it rotates in contact with the air bearing 24. Next, as the rotation speed of the rotating shaft 23 increases, it transitions from the touchdown state S1 to a levitation support state S2. The rotating shaft 23 increases in rotation speed to a speed defined as the rated operating state.

[0088] The relationship between the elapsed time from the start of the motor 2 to rated operation and the frequency fsw of the output voltage pulse P may be defined by equation (2). Equation (2) is a definition using the average of the frequency fws of the output voltage pulse P with respect to time T.

number

[0089] The left side of equation (2) is the average of the switching frequency fws over time T when in the levitated state. The right side of equation (2) is the average of the switching frequency fws over time T when in the non-levitated state. For example, the average of the switching frequency fws over time T when in the non-levitated state is the time average value obtained by dividing the area of ​​region K1 surrounded by the X-axis, Y-axis, and line representing time Tr, and line L2 representing the relationship between time T and switching frequency fsw, by the reference time (Tr-Ts) of the non-levitated time region T1, as shown in Figure 11. The area of ​​region K1 is the value obtained by integrating the frequency of the first output voltage pulse over time.

[0090] The average of the switching frequency fws over time T when in the levitated state is the area of ​​region K2 divided by the reference time (Tm-Tc) of the levitation time region T3. The area of ​​region K2 is the time average value obtained by integrating the frequency of the second output voltage pulse over time. The relationship between time T and the carrier wave switching frequency fsw can be defined as follows: the average of the switching frequency fws over time when in the non-levitated state is smaller than the average of the switching frequency fws over time T when in the levitated state (see equation (2)).

[0091] <Other variations> The present disclosure is not limited to the above-described examples, and various other modifications are possible. For example, the above-described embodiment discloses an example in which the switching frequency in the non-floating rotation speed range N1 never exceeds the minimum value of the switching frequency in the floating rotation speed range N3. However, this frequency condition is not essential. For example, it does not exclude the switching frequency temporarily exceeding the minimum value of the switching frequency in the floating rotation speed range N3 when in the non-floating rotation speed range N1. [Explanation of symbols]

[0092] 1.1A motor drive unit (electric motor operating unit) 2. Motor (electric motor) 3 DC power supply 11 Inverter (power conversion section) 12,12A Inverter control unit (control unit) 21 rotor 22 Stator 23 Rotation axis 24 Air bearing 25 Floating detection sensor 121 modulation factor calculation unit (first calculation unit) 122 Switching frequency calculation unit (third calculation unit) 123 PWM control signal calculation unit (second calculation unit) 124 Air bearing levitation signal acquisition unit S1 Touchdown state S2 Floating support state N rotation speed N1 Non-floating RPM range N2: Free rotation speed range N3 Floating RPM range Ns Lower limit of non-floating rotation speed Nr Floating RPM (Upper limit non-floating RPM) Nm Maximum floating speed (Upper limit floating speed) Nc Marginal rotation speed (lower limit floating rotation speed)

Claims

1. a power conversion unit electrically connected to the electric motor having the fluid dynamic bearing and operating based on a pulse control method; a control unit that supplies a control signal to the power conversion unit to control an operation of the power conversion unit, The control unit outputting the control signal including a carrier wave having a first frequency to the power conversion unit when the fluid bearing is not in a floating support state; outputting the control signal including a carrier wave having a second frequency to the power conversion unit when the fluid bearing is in a floating support state; The first frequency is lower than the second frequency.

2. The control unit a first calculation unit that sets a modulation factor of the control signal; a second calculation unit that sets the frequency of the carrier wave; a third calculation unit that obtains the control signal using the modulation factor set by the first calculation unit and the frequency of the carrier wave set by the second calculation unit.

3. 3. The electric motor operating device according to claim 2, wherein the second calculation unit sets the frequency of the carrier wave to either the first frequency or the second frequency using information related to the rotation speed of the rotating shaft of the electric motor supported by the fluid bearing.

4. The second calculation unit setting the frequency of the carrier wave to the first frequency when the rotation speed is in a non-floating rotation speed range that is less than a preset floating rotation speed and when the rotation speed is in a range that is less than a margin rotation speed that is equal to or greater than the floating rotation speed and is equal to or greater than the floating rotation speed; 4. The electric motor operating device according to claim 3, wherein the frequency of the carrier wave is set to the second frequency when the rotational speed is in a levitation rotational speed range that is equal to or higher than the margin rotational speed.

5. The second calculation unit When the rotation speed is in the non-floating rotation speed range and the margin rotation speed range, the first frequency is set to a first constant value that is not based on the rotation speed; When the rotation speed is in the levitation rotation speed range, the second frequency is set to a second constant value that is not based on the rotation speed; 5. The motor operating device of claim 4, wherein the first constant value is less than the second constant value.

6. The second calculation unit When the rotation speed is in the non-floating rotation speed range and the margin rotation speed range, the first frequency is set to a constant value that is not based on the rotation speed; 5. The electric motor operating device according to claim 4, wherein when the rotation speed is in the levitation rotation speed range, the second frequency is set to a value that increases as the rotation speed increases, with the first frequency as a starting value.

7. The second calculation unit When the rotation speed is in the non-floating rotation speed range and the margin rotation speed range, the first frequency is set to a constant value that is not based on the rotation speed; 5. The electric motor operating device according to claim 4, wherein when the rotation speed is in the levitation rotation speed range, the second frequency is set to a value that increases as the rotation speed increases, starting from a value higher than the first frequency.

8. The second calculation unit When the rotation speed is in the non-floating rotation speed range and the margin rotation speed range, the first frequency is set to a constant value that is not based on the rotation speed; When the floating rotation speed range is the range, at least a first floating rotation speed range and a second floating rotation speed range having a rotation speed higher than that of the first floating rotation speed range are set, When the rotation speed is in the first levitation rotation speed range, the second frequency is set to a first constant value that is higher than the first frequency and is not based on the rotation speed; 5. The electric motor operating device according to claim 4, wherein when the rotation speed is in the second levitation rotation speed range, the second frequency is set to a second constant value that is higher than the first constant value and is not based on the rotation speed.

9. The second calculation unit When the rotation speed is in the non-floating rotation speed range and the margin rotation speed range, the first frequency is set to a constant value that is not based on the rotation speed; When the floating rotation speed range is the range, at least a first floating rotation speed range and a second floating rotation speed range having a rotation speed higher than that of the first floating rotation speed range are set, When the rotation speed is in the first levitation rotation speed range, the second frequency is set to a first constant value that is higher than the first frequency and is not based on the rotation speed; 5. The electric motor operating device according to claim 4, wherein when the rotation speed is in the second levitation rotation speed range, the second frequency is set to a value that increases as the rotation speed increases, starting from the first constant value.

10. The second calculation unit When the rotation speed is in the non-floating rotation speed range and the margin rotation speed range, the first frequency is set to a value that increases with an increase in the rotation speed; 5. The electric motor operating device according to claim 4, wherein when the rotation speed is in the levitation rotation speed range, the second frequency is set to a value that increases as the rotation speed increases, with the first frequency as a starting value.

11. the control unit sets the frequency of the carrier wave to either the first frequency or the second frequency by utilizing information related to the rotation speed (N) of the rotating shaft of the electric motor supported by the fluid bearing and a relationship between the rotation speed (N) and the frequency of the carrier wave; The control unit acquires information defined by a non-floating rotation speed range defined by an upper limit non-floating rotation speed (Nr) and a floating rotation speed range defined by an upper limit floating rotation speed (Nm), The relationship between the rotation speed (N) and the frequency of the carrier wave is as follows: a non-floating ratio ((fswb-fswc) / Nr) defined by a difference (fswb-fswc) between the non-floating maximum frequency (fswb) of the carrier wave when not in the levitation support state and the non-floating minimum frequency (fswc) of the carrier wave when not in the levitation support state, and the preset upper limit non-floating rotation speed (Nr); a floating ratio (fsw1 / Nm) defined by a maximum floating frequency (fsw1) of the carrier wave when in the floating support state and the upper limit floating rotation speed (Nm) associated with the maximum floating frequency (fsw1), 2. The electric motor operating device according to claim 1, wherein the floating ratio (fsw1 / Nm) is greater than the non-floating ratio ((fswb-fswc) / Nr).

12. the control unit sets the frequency of the carrier wave to either the first frequency or the second frequency by utilizing information related to the rotation speed (N) of the rotating shaft of the electric motor supported by the fluid bearing and a relationship between the rotation speed (N) and the frequency of the carrier wave; The relationship between the rotation speed (N) and the frequency of the carrier wave is as follows: an upper limit non-floating rotation speed (Nr) indicating the upper limit of the rotation speed (N) of the rotating shaft when the fluid bearing is not in a floating support state; a lower limit non-floating rotation speed (Ns) indicating the lower limit of the rotation speed (N) of the rotating shaft when the fluid bearing is not in a floating support state; The relationship between the rotation speed (N) of the rotating shaft when the fluid bearing is not in a floating support state and the frequency of the carrier wave corresponding to the rotation speed (N) of the rotating shaft is expressed as a function (f １ (N)) and an upper limit of the floating rotation speed (Nm) indicating the upper limit of the rotation speed (N) of the rotating shaft when the fluid bearing is in a floating support state; a lower limit floating rotation speed (Nc) indicating the lower limit of the rotation speed (N) of the rotating shaft when the fluid bearing is in a floating support state; The relationship between the rotation speed (N) of the rotating shaft when the fluid bearing is in a floating support state and the frequency of the carrier wave corresponding to the rotation speed (N) of the rotating shaft is expressed as a function (f ２ (N)) and satisfy the condition shown by formula (1) including [Equation 1] 2. The motor operating device of claim 1.

13. the control unit further includes a signal acquisition unit that receives a signal indicating whether or not the rotating shaft of the electric motor supported by the fluid bearing has floated; The electric motor operating device according to claim 2 , wherein the second calculation unit sets the frequency of the carrier wave by using the signal acquired by the signal acquisition unit.

14. a power conversion unit electrically connected to the electric motor having the fluid dynamic bearing and operating based on a pulse control method; The power conversion unit outputting a first output voltage pulse when the fluid bearing is not in a floating support state; outputting a second output voltage pulse when the fluid bearing is in a floating support state; The frequency of the first output voltage pulse is lower than the frequency of the second output voltage pulse.

15. 15. The electric motor operating device according to claim 14, wherein a time average value obtained by dividing a value obtained by integrating the frequency of the second output voltage pulse with respect to time by a reference time is smaller than a time average value obtained by dividing a value obtained by integrating the frequency of the first output voltage pulse with respect to time by the reference time.

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