WO2024019003A1 - Torque pulsation measurement method and torque pulsation measurement device for permanent magnet motor and method for manufacturing permanent magnet motor - Google Patents

Abstract

The present disclosure provides a torque pulsation measurement method for a permanent magnet motor provided with a stator that has an iron core guiding magnetic flux and a coil insulated from the iron core and capable of generating a rotating magnetic field, a rotor that has a magnet generating magnetic flux and that is rotatably fixed to the stator guiding magnetic flux, and a velocity detector that detects the mechanical angular velocity of the rotor. The torque pulsation measurement method includes a calculation step for calculating, in a state in which an output shaft of the permanent magnet motor is not driven from outside and is driven by the permanent magnet motor, torque pulsation by decomposing each angular acceleration obtained by differentiating the mechanical angular velocity detected by the velocity detector into a frequency component of an order that is an integral multiple of a rotation angle and multiplying the frequency component by an inertia moment.

Description

Permanent magnet motor torque pulsation measurement method, torque pulsation measurement device, and permanent magnet motor manufacturing method

The present disclosure relates to a method of measuring torque pulsations that occur during rotation of a permanent magnet motor.

In the torque pulsation measuring method disclosed in Patent Document 1 below, a torque sensor is provided between a test motor to be measured and a load motor, and the test motor is rotated by the load motor, and the torque pulsation generated at that time is Measuring torque fluctuations.

In addition, in the torque pulsation measuring method disclosed in Patent Document 2 below, torque fluctuations are calculated from a command value of current applied to a test motor controlled at a constant speed, without using a load motor or a torque sensor. are doing.

Japanese Patent Application Publication No. 2005-188941 Japanese Patent Application Publication No. 7-210221

The method of Patent Document 1 requires a process of connecting a load motor and a torque sensor, and this process hinders productivity improvement. Furthermore, there is a problem in that the cost of a measuring device such as a torque sensor is required, leading to an increase in production costs.

In the method of Patent Document 2, keeping the speed constant is a necessary condition for realizing measurement. When feedback control is performed as described in Patent Document 2, the deviation from the command speed is fed back to the torque, so speed fluctuations always occur and constant speed control cannot be performed. When speed pulsation exists, there is a problem in that a torque pulsation component that depends on inertia torque occurs, resulting in an error in the measurement of torque pulsation.

The present disclosure has been made to solve the above-mentioned problems, and does not require mechanical connection of a load motor or a torque sensor to a permanent magnet motor, and eliminates torque pulsation even in a state where constant speed control is not possible. The purpose of this invention is to provide a torque pulsation measurement method that can measure torque pulsation.

A permanent magnet motor torque pulsation measuring method according to the present disclosure includes a permanent magnet motor that includes an iron core that guides magnetic flux, a stator that has a coil that is insulated from the iron core and that can generate a rotating magnetic field, and a magnet that generates magnetic flux. It has a rotor rotatably fixed to a stator that guides magnetic flux, and a speed detector that detects the mechanical angular velocity of the rotor. The torque pulsation measurement method is to measure each angular acceleration obtained by differentiating the mechanical angular velocity detected by a speed detector while the output shaft of the permanent magnet motor is not driven externally and is driven by the permanent magnet motor. It includes a calculation step of calculating torque pulsation by decomposing the angle into frequency components of orders that are integral multiples and multiplying by the moment of inertia.

Further, the method for manufacturing a permanent magnet motor according to the present disclosure includes a step of determining the quality of the permanent magnet motor based on the torque pulsation calculated using the torque pulsation measuring method, after the permanent magnet motor is assembled.

Further, in the torque pulsation measuring device for a permanent magnet motor according to the present disclosure, the permanent magnet motor includes an iron core that guides magnetic flux, a stator that is insulated from the iron core and has a coil that can generate a rotating magnetic field, and a stator that generates magnetic flux. It includes a rotor that is rotatably fixed to a stator that has a magnet and guides magnetic flux, and a speed detector that detects the mechanical angular velocity of the rotor. The torque pulsation measuring device measures each angular acceleration obtained by differentiating the mechanical angular velocity detected by the speed detector while the output shaft of the permanent magnet motor is not driven externally and is driven by the permanent magnet motor. It includes the step of calculating the inertial torque pulsation obtained by decomposing the angle into frequency components of orders that are integral multiples and multiplying by the moment of inertia.

According to the present disclosure, even in a state where there is speed variation, in addition to current variation, acceleration variation can be frequency converted and torque pulsation can be calculated using the moment of inertia. Therefore, torque pulsation can be measured without requiring mechanical connection of a load motor or a torque sensor to the permanent magnet motor to be measured.

FIG. 3 is a diagram showing a control block of the torque pulsation measuring method according to the first embodiment. FIG. 2 is a schematic diagram showing a permanent magnet motor that is a measurement target. It is a figure which shows the signal output by the encoder as a position detector when a rotor is rotated in the forward direction. 3 is a flowchart illustrating an example of a procedure of a torque pulsation measuring method. FIG. 2 is a hardware configuration diagram of a control device that implements the torque pulsation measuring method according to the first embodiment. 7 is a diagram showing an operation flow of the torque pulsation measuring device according to Embodiment 3. FIG.

Hereinafter, embodiments will be described with reference to the drawings. Common or corresponding elements in each figure are denoted by the same reference numerals, and description thereof will be simplified or omitted.

Embodiment 1.
FIG. 1 is a diagram showing a control block of the torque pulsation measuring method according to the first embodiment. FIG. 2 is a schematic diagram showing a permanent magnet motor (hereinafter referred to as "motor") Mt that is a measurement target.

The motor Mt includes a stator 1 and a rotor 2. The stator 1 has an iron core 10 made of a laminated body through which magnetic flux passes. The iron core 10 has a plurality of teeth 11 that are evenly arranged in the circumferential direction, which is the direction of rotation, and each extend in the radial direction. Three-phase windings 12 represented by a U-phase winding 12U, a V-phase winding 12V, and a W-phase winding 12W are provided between adjacent teeth 11 through predetermined connections. Insulators made of insulating paper 13 or resin are inserted between the windings 12 and the iron core 10 and between adjacent windings 12 in order to insulate them from each other.

The rotor 2 is provided inside the stator 1 in the radial direction. A magnet 21 is provided on the outer surface of the rotor 2 in the radial direction. A yoke 22 for passing magnetic flux is provided on the inner peripheral side of the magnet 21. A shaft 23 is provided at the center of the yoke 22, and is rotatably held by a bearing (not shown).

The magnetic flux generated by energizing the winding 12 attracts or repels the magnetic flux created by the magnet 21 of the rotor 2, and the magnetic flux generated by energizing the winding 12 attracts the iron of the rotor 2. This generates torque and rotates the rotor 2.

The magnitudes of the d-axis current I _d and the q-axis current I _q in the coordinate system of the d-axis and q-axis rotating together with the rotor 2 are the current I _U flowing through the U-phase winding 12U and the current I flowing through the V-phase winding 12V. _V , the current _IW flowing through the W-phase winding 12W, and the electrical angle _θe of the rotor 2, it can be expressed as in the following equation (1).

The torque τ(t) generated by the motor Mt is expressed by the following formula (2) using the d-axis current I _d , the q-axis current I _q , the induced voltage constant K _a , the d-axis inductance L _d , and the q-axis inductance L _q It can be expressed as

In the above formula (2), N _p is the number of pole pairs, and is a parameter determined when designing the motor Mt. In the case of the motor Mt shown in FIG. 2, the number of pole pairs _Np is five. When the moment of inertia of the rotor 2 is J and the mechanical angular velocity is ω _m , the equation of motion around the rotor 2 is expressed as the following equation (3).

Here, τ _ε (t) is a disturbance component, which is loss torque generated in bearings, lubricant sealing structures, etc., and torque generated due to magnets and iron attracting each other between rotor 2 and stator 1. . Among these, a component that changes depending on the rotation angle is called torque pulsation, which causes vibration and instability in position and speed control. Since torque loss is generally known to be speed dependent, it is undesirable to measure torque pulsation under conditions where there are large speed fluctuations. Therefore, feedback control is performed so that the motor Mt can be operated so that the mechanical angular velocity detected by a speed detector, which will be described later, is kept as constant as possible.

The moment of inertia J of the rotor 2 can be grasped as a parameter of the motor Mt when designing the motor Mt. The moment of inertia J is also called inertia. The induced voltage constant K _e can be calculated by rotating the rotor 2 at a speed of ω _r with no current flowing, setting the d-axis current I _d to 0 and the q-axis current I _q to 0, and using the following equation (4). It can be obtained by solving the following equation (5), which is derived by setting the d-axis voltage V _d =0. In the following equations (4) and (5), Vq is the q-axis voltage.

Next, the operation control state of the motor Mt in this embodiment will be explained.

The speed command unit 31 gives a predetermined operating speed ω _o as the command speed. The operating speed corresponds to the rotation speed. The speed calculation unit 32 differentiates the position signal input from the position detector 41 attached to the motor Mt, and outputs a speed signal obtained by the differentiation. The speed signal corresponds to the actual speed. The speed signal from the speed calculation section 32 is subtracted from the command speed ω _o from the speed command section 31, and the speed difference, which is the subtracted value, is input to the torque command section 33. The torque command unit 33 calculates the command torque such that the speed signal is slow relative to the command signal, the speed signal is accelerated, and the speed signal is fast relative to the command signal, the speed signal is decelerated. If the calculation in the torque command unit 33 is only proportional control, it will oscillate and not converge, so it is desirable to combine differential control and integral control.

The current control unit 34 calculates the q-axis current _Iq and d-axis current _Id that satisfy the command torque calculated by the torque command unit 33, and can realize the calculated q-axis current _Iq and d-axis current _Id . Calculate the U-phase current, V-phase current, and W-phase current. Each phase current corresponds to a switching command for the elements of the inverter 42. The inverter 42 determines a duty ratio so that the current for each phase is calculated by the current control unit 34, and applies a voltage supplied from a bus (not shown) to the motor Mt. The motor Mt generates a torque that accelerates or decelerates by applying voltage, that is, by driving current. The position of the motor Mt is detected by a position detector 41.

The current calculation unit 35 measures the drive current flowing through the motor Mt by voltage application from the inverter 42, and provides feedback to the current control unit 34 so that the q-axis current _Iq and the d-axis current _Id become desired currents. put on.

As the position detector 41, for example, an encoder (not shown) can be used. The encoder outputs an A-phase signal and a B-phase signal according to the mechanical angular velocity of the rotor 2. It is assumed that the A-phase signal switches at a cycle of RES times while the rotor 2 rotates once, and the B-phase signal switches at a cycle of RES times while the rotor 2 rotates once. FIG. 3 is a diagram showing a signal output by the encoder when the rotor 2 is rotated in the forward direction. For example, when the rotor 2 is rotating in the forward direction, the A-phase signal changes from the low potential side to the high potential side after a period of time t0 during which the rotor 2 rotates by a certain rotation angle has elapsed. After that, when time t0 further elapses, the A-phase signal changes from the high potential side to the low potential side. Further, the B-phase signal switches between the high potential side and the low potential side with a time difference of "t0÷2" from the A-phase signal. In this embodiment, after the A-phase signal rises from the low-potential side to the high-potential side, the B-phase signal changes from the low-potential side to the high-potential side at the timing when time "t0÷2" has elapsed. . Further, after the A-phase signal falls from the high potential side to the low potential side, the B-phase signal changes from the high potential side to the low potential side at a timing when time "t0/2" has elapsed. The position detector 41 and the speed calculation section 32 correspond to a speed detector. Feedback control is performed so that the mechanical angular velocity detected by this speed detector maintains a constant operating speed _ωo .

Details of the current pulsation calculation unit 36, speed pulsation calculation unit 37, and torque pulsation calculation unit 38 represented in the other control blocks will be described later. Note that the speed calculation section 32, torque command section 33, current control section 34, current calculation section 35, current pulsation calculation section 36, speed pulsation calculation section 37, and torque pulsation calculation section 38 are based on a program stored in the memory 30b, which will be described later. This is a function calculated by the processor 30a executing.

Next, the torque pulsation measurement procedure (calculation process) will be explained. FIG. 4 is a flowchart showing an example of the procedure of the torque pulsation measuring method.

First, the rotor 2 is rotated at high speed (step S1). In step S1, a voltage V UV generated between the U-phase winding 12U leading to the U-phase power supply and the V-phase winding 12V leading to the V-phase power supply, and the voltage V _UV generated between the V-phase winding 12V and the W-phase power supply Measure the voltage V _VW generated between the W-phase winding 12W leading to the W-phase winding 12W. The voltage V _WU generated between the W-phase winding 12W and the U-phase winding 12U may be determined by V _WU = -V _UV -V _VW , or may be directly measured. The d-axis voltage _Vd is calculated using the measured voltage and the rotation angle of the rotor 2, and the phases of the position detector 41 and the rotor 2 are matched so that _Vd becomes small. Note that when the phases of the position detector 41 and the rotor 2 are matched in advance using an absolute position detection sensor, such a step of matching the phases can be made unnecessary.

Subsequently, the rotor 2 is rotated at low speed (step S2). In step S2, when the magnitude of the amplitude of the torque pulsation to be detected is τ _r and the frequency of the torque pulsation with respect to the rotation angle, which is a mechanical angle, is f, the rotational speed ω _m , which is the mechanical angular velocity of the rotor 2, is ω _m × The rotational speed ω _m is determined so as to satisfy the relationship f<τ _r .
Note that in steps S1 and S2, no load for rotating the rotor 2 is attached to the rotor 2, and the output shaft of the motor Mt is not driven from the outside but is in a self-propelled state driven by the motor Mt. It's rotating.

When the frequency for the mechanical angle to be analyzed is f, the number of signal switching RES of the position detector 41 is preferably selected such that M in the following equation (6) is an integer.

When the frequency for the mechanical angle to be analyzed is f, the signal switching frequency RES of the position detector 41 is preferably selected such that M in the following equation (6) is an integer.
RES×4=f×M...(6)

Further, when the rotational speed ω _m of the rotor 2 sufficiently follows the speed command ω ₀ , the time required for one rotation is expressed by the following equation (7).
2π÷ω ₀ ...(7)

Therefore, since the time of frequency f with respect to the mechanical angle to be analyzed is expressed by the following equation (8), it is possible to record a time that is an integral multiple of this.
2π÷ω ₀ ÷f...(8)

At this time, when a large number of frequency components other than the frequency f for the mechanical angle to be analyzed are included, it is desirable to determine the measurement time so that it is an integral multiple of those frequency components.

Note that when the rotor 2 rotates in the opposite direction to the forward direction, the order in which the A-phase signal and the B-phase signal change is reversed. In this case, after the B-phase signal changes from the low potential side to the high potential side, the A-phase signal changes from the low potential side to the high potential side at a timing when time "t0÷2" has elapsed. Similarly, after the B-phase signal changes from the high potential side to the low potential side, the A-phase signal changes from the high potential side to the low potential side at a timing when time "t0÷2" has elapsed.

Next, a first method of calculating the rotational speed of the rotor 2 will be explained. To calculate the rotation speed, we need to calculate the switching of the A-phase signal from the low potential side to the high potential side, the switching of the A-phase signal from the high potential side to the low potential side, and the B-phase signal that occurs during a certain period of time Δt. The number of times the B-phase signal switches from the low potential side to the high potential side and the B phase signal switches from the high potential side to the low potential side are measured. Assuming that the number of times of switching during the time Δt is n, the rotational speed ω _m of the rotor 2 can be obtained as shown in the following equation (9).

A second calculation method for the rotational speed of the rotor 2 will be explained. Using the aforementioned encoder signal, the A-phase signal changes from low potential side to high potential side, or vice versa, and then the B-phase signal changes from low potential side to high potential side, or vice versa. Using the time interval Δt2, it can be calculated as shown in the following equation (10).

If there is a sufficient change in the signal in the time interval of Δt in the above equation (9), the first calculation method for the rotational speed of the rotor 2 is effective, but if there is a sufficient change in the signal in the time interval of Δt, If this is not possible, it will not be possible to detect minute changes in the rotor's rotational speed. Conversely, if the value of the speed calculation period Δt is increased, a delay occurs in the rotor speed feedback, which deteriorates speed stability, which is not preferable.

The magnitude of torque pulsation does not substantially change depending on the rotational speed of the rotor 2. Consider a state in which the average loss torque and the motor Mt are balanced. Letting the velocity amplitude be A, a relationship as shown in the following equation (11) holds true.

In the above formula (11), ω is the mechanical angular frequency. When the above equation (11) is solved for the velocity amplitude A, the following equation (12) is obtained.

According to the above equation (12), it can be seen that the faster the rotational speed of the rotor 2, the smaller the speed amplitude A becomes. Depending on the resolution of the rotational speed fluctuation of the rotor 2 and the accuracy of the target torque pulsation to be measured, it is necessary to satisfy the relationship shown in the following equation (13). Therefore, in order to ensure measurement accuracy, it is preferable to slow down the rotational speed of the rotor 2.

Next, a method for calculating current torque pulsations, which are pulsations in the rotational speed of the rotor 2, and inertia torque pulsations, which are pulsations in acceleration, in the speed pulsation calculation unit 37 will be described. The speed in the speed calculation period is calculated from the first calculation method or the second calculation method of the rotational speed of the rotor 2 at each time. Next, by differentiating the obtained velocity with respect to the analysis time, the angular acceleration of the rotor 2 at that time can be calculated. In the differentiation of discrete values, use central differentiation, and divide the difference between the velocity one point before the time you want to find and the speed one point after the time you want to find by twice the time interval. Arithmetic is preferred. This is because the error can be made smaller compared to forward and backward differences, and when forward and backward differences are used, the time shifts from the center, but with centered differences, such time shifts do not occur. .

A second calculation method for calculating the differential value is a method using Fourier transform. The measurement result ω _e (t) of the rotational speed of the rotor 2 is expressed as in the following equation (14).

The coefficient A _k in each order component can be determined by Fourier transformation. Here, T ₀ is the time of the analysis interval, N is the number of data points in the analysis interval, and i is an imaginary unit. The coefficient A _k from 1 to N÷2 can be obtained using Fourier transform as shown in equation (15) below.

Here, exp(ix) is an exponential function of a complex number, and has a relationship as shown in equation (16) below. i is an imaginary unit.

For this calculation, a method that obtains the same result as using the above formula is a widely known method called the Cooley-Tukey type algorithm, which calculates components of each order at high speed, and it is possible to use this algorithm. can.

From the relationship in equation (17) above, the components of the angular acceleration of the rotor 2 in each order can be calculated. In this case, even if the speed calculation cycle and the data acquisition cycle do not match, the change in speed can be easily calculated.

Therefore, by converting the frequency of fluctuations in angular acceleration, it is possible to calculate the pulsating component of inertial torque, which is a remarkable effect not seen in the past.

Next, the current pulsation calculation unit 36 energizes the motor Mt to measure the pulsation of torque generated by the motor Mt (step S3). The method for measuring torque pulsation will be explained below. The d-axis current I _d and the q-axis current I _q are determined using the above equation (1). The value of the torque generated by the motor Mt at each time is calculated using the known induced voltage constant K _a , d-axis inductance L _d , q-axis inductance L _q and the above equation (2).

Similar to when calculating the angular acceleration by differentiating the rotational speed of the rotor 2, the frequency component T _k of the torque generated by the motor Mt is calculated by dividing into each order component as shown in the following equation (18).

The frequency component T _k of the torque from 1 to N÷2 can be obtained as shown in the following equation (19) using Fourier transform.

Finally, a method for determining the torque pulsation τ _ε generated by the magnet and iron attracting each other between the rotor 2 and the stator 1 in the torque pulsation calculation unit 38 will be explained using the above equation (3). By substituting the above equation (17) and the above equation (18) into the above equation (3), the following equation (20) is obtained.

When the above equation (20) is solved for the torque pulsation τ _ε , the following equation (21) is obtained.

Since exp(i×x) are orthogonal to each other, torque ripples τ _ε of components orthogonal to the mechanical angle, that is, components of the same frequency are added together. The torque pulsation of the desired order can be obtained by the following equation (22) by analyzing data at a time K times the order of the desired torque pulsation.
T _K - J×A _K ×i×2Kπ÷T ₀ ...(22)

At this time, the amplitude A _k of the torque pulsation can be expressed as in the following equation (23) using the absolute value of a complex number.
｜T _K - J×A _K ×i×2Kπ÷T ₀ |...(23)

FIG. 5 is a hardware configuration diagram of the control device 3 as a torque pulsation measuring device (also see Embodiment 3 described later) that implements the above torque pulsation measuring method. The control device 3 corresponds to a computer that can execute a torque pulsation measurement program, and can be realized by a processing circuit. For example, the processing circuit includes at least one processor 30a and at least one memory 30b.

When the processing circuit includes at least one processor 30a and at least one memory 30b, each function of the control device 3 is realized by software, firmware, or a combination of software and firmware. At least one of the software and firmware is written as a program. At least one of software and firmware is stored in at least one memory 30b. At least one processor 30a reads and executes a program stored in at least one memory 30b. At least one processor 30a is also referred to as a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. For example, at least one memory 30b is a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, EEPROM, magnetic disk, flexible disk, optical disk, compact disk, mini disk, DVD, etc.

Additionally, the processing circuit may be configured to include at least one dedicated hardware (not shown). In this case, the processing circuit is implemented, for example, as a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

As explained above, in this embodiment, since the torque pulsation is measured by adding the pulsating component of the current, an external sensor and a load motor are required compared to the case where only the pulsating component of the inertial torque is calculated. Torque pulsation can be measured with high accuracy without Furthermore, compared to calculations using only current pulsations, since speed fluctuations contribute to torque pulsations, torque pulsations can be measured with high accuracy without the need for external sensors or load motors.

Note that the measurement of torque pulsation as described above is performed in a process such as a shipping test of the permanent magnet motor Mt after the permanent magnet motor Mt is assembled. At this time, it is possible to determine whether the permanent magnet motor Mt is good or bad based on the measured torque pulsation, for example, based on a comparison result between the measured torque pulsation and a threshold value. The process of determining the quality of the permanent magnet motor Mt in this way can constitute a method of manufacturing the permanent magnet motor Mt.

Embodiment 2.
The second embodiment differs from the first embodiment in that the d-axis current _Id commanded to the inverter 42 is kept constant. This difference will be mainly explained below. By substituting I _d (t)=I _d into the above equation (2), it can be transformed as shown in the below equation (24).

At this time, since the torque τ(t) generated by the motor Mt is time dependent only on I _q (t), the frequency component of the torque generated by the motor Mt in the above equation (18) can be expressed as in the below equation (25). It can be expressed as

According to the present embodiment, by keeping the d-axis current I _d constant, it becomes easy to calculate the magnitude of the torque generated by the motor Mt, and it is possible to reduce the causes of measurement errors in torque pulsation. As a result, the measurement accuracy of torque pulsation can be improved.

Furthermore, when the d-axis current I _d is set to 0, the torque pulsation can be obtained without depending on the d-axis inductance L _d or the q-axis inductance L _q , and the calculation of the torque pulsation can be simplified. desirable. In addition, when the d-axis current flows, torque pulsations depending on the induced voltage harmonics may occur, so by setting the d-axis current I _d to 0, the generated torque pulsations can be reduced, and the torque The measurement accuracy of pulsation can be improved.

Embodiment 3.
FIG. 6 is a diagram showing an operation flow of the torque pulsation measuring device according to the third embodiment. In this embodiment, torque pulsation is measured by the procedure shown in FIG.

First, in step 1, the motor Mt is attached to the torque pulsation measuring device (control device 3). Next, in step 2, the motor Mt is rotated by free running, and the voltage between the terminals of the motor Mt (for example, the line voltage between the U phase and the V phase) and rotation speed are measured after the power is cut off. . Next, in step 3, the induced voltage constant T _k is calculated by dividing the voltage measured in step 2 by the rotational speed. It is also possible to calculate the speed in step 3 from the period of voltage fluctuation without measuring the speed in step 2, and to calculate the induced voltage constant T _k using the calculated speed. Next, in step 4, the motor Mt is rotated by a constant speed command. As in the first embodiment, current and speed are acquired. Next, in step 5, torque pulsation is calculated using the induced voltage constant _Tk calculated in step 3 and the speed and current obtained in step 4, as in the first embodiment. By calculating the induced voltage constant _Tk before step 5, the target torque fluctuation can be quickly measured after step 4. When the measurement is completed, the motor Mt is removed in step 6. Although steps 2 and 3 may be performed after step 5, it is preferable to perform them before step 5.

According to the present embodiment, a torque pulsation measuring device that can measure torque pulsation with high accuracy, similar to Embodiment 1, is obtained.

1... Stator, 10... Iron core, 12... Winding, 2... Rotor, 21... Magnet, 3... Control device (torque pulsation measuring device), 41... Position detector (speed detector), J... Moment of inertia

Claims (10)

1. An iron core that guides magnetic flux, a stator that has a coil that is insulated from the iron core and can generate a rotating magnetic field, and a rotor that has a magnet that generates magnetic flux and is rotatably fixed to the stator that guides the magnetic flux. and a method for measuring torque pulsation of a permanent magnet motor, comprising a speed detector that detects the mechanical angular velocity of the rotor,
   In a state where the output shaft of the permanent magnet motor is not driven externally and is driven by the permanent magnet motor, each angular acceleration obtained by differentiating the mechanical angular velocity detected by the speed detector is calculated with respect to the rotation angle. A method for measuring torque pulsation of a permanent magnet motor, which includes a calculation step of calculating the inertial torque pulsation obtained by decomposing the frequency components into integral multiple order frequency components and multiplying them by the moment of inertia.
2. The method for measuring torque pulsation of a permanent magnet motor according to claim 1, wherein feedback control is performed so that the mechanical angular velocity detected by the speed detector maintains a specified constant speed.
3. Current torque pulsation calculated by decomposing the rotation angle caused by the current flowing through the permanent magnet motor into frequency components of an order of an integral multiple, and multiplying this by an induced voltage constant, and the same frequency component of the inertial torque pulsation. 3. The method for measuring torque pulsation of a permanent magnet motor according to claim 1 or 2, wherein the torque pulsation is calculated by adding up the torque pulsation.
4. The method for measuring torque pulsation of a permanent magnet motor according to any one of claims 1 to 3, wherein the permanent magnet motor is driven with a constant d-axis current and torque pulsation is calculated.
5. The method for measuring torque pulsation of a permanent magnet motor according to any one of claims 1 to 3, wherein the permanent magnet motor is driven with a d-axis current of 0 and torque pulsation is calculated.
6. After the permanent magnet motor is assembled, the step of determining whether the permanent magnet motor is good or bad based on the torque pulsation calculated using the torque pulsation measuring method according to any one of claims 1 to 3. A method of manufacturing a permanent magnet motor, including:
7. An iron core that guides magnetic flux, a stator that has a coil that is insulated from the iron core and can generate a rotating magnetic field, and a rotor that has a magnet that generates magnetic flux and is rotatably fixed to the stator that guides the magnetic flux. and a torque pulsation measuring device for a permanent magnet motor, comprising a speed detector that detects the mechanical angular velocity of the rotor,
   In a state where the output shaft of the permanent magnet motor is not driven externally and is driven by the permanent magnet motor, each angular acceleration obtained by differentiating the mechanical angular velocity detected by the speed detector is calculated with respect to the rotation angle. A torque pulsation measurement device for a permanent magnet motor, which includes a step of calculating inertial torque pulsation obtained by decomposing the frequency components into integral multiple order frequency components and multiplying them by the moment of inertia.
8. The torque pulsation measuring device for a permanent magnet motor according to claim 7, wherein feedback control is performed so that the mechanical angular velocity detected by the speed detector maintains a specified constant speed.
9. Electromagnetic torque pulsation calculated by decomposing the rotation angle caused by the current flowing in the permanent magnet motor into frequency components of an order of an integral multiple, and multiplying this by an induced voltage constant, and a component of the same frequency of the inertial torque pulsation. The torque pulsation measuring device for a permanent magnet motor according to claim 7 or 8, wherein the torque pulsation is calculated by adding up the torque pulsation.
10. The torque pulsation measuring device for a permanent magnet motor according to any one of claims 7 to 9, characterized in that an induced voltage constant is measured before and after measuring torque pulsations.

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