JP5828710B2 - Method for determining the characteristics of an electric motor using a permanent magnet as a rotor - Google Patents

Description

The present invention relates to a determination method for checking the characteristics of an electric motor using a permanent magnet as a rotor, for example, after maintenance.

After disassembling the motor and servicing its components (cleaning, repairing or replacing as necessary), when the motor is reassembled, the magnetic force of the permanent magnets attached to the rotor helps maintain the motor. Accordingly, it is an important matter to determine whether or not demagnetization has occurred.
Here, the magnetic force (presence / absence of demagnetization) of the permanent magnet used in the electric motor can be confirmed by measuring the current value when the electric motor is rotated using an inverter. There is a problem that a dedicated inverter must be used in accordance with the capacity. Therefore, for example, Patent Document 1 measures the period and effective value of an induced voltage waveform generated after an electric motor is driven using an inverter and the power is turned off in a state where the electric motor is at a steady rotational speed. A method of confirming the magnetic force (magnetization factor) of a permanent magnet by comparing the period and effective value of the induced voltage waveform with a reference value is disclosed.

JP 2003-284296 A

However, when the method of Patent Document 1 is applied to a motor after maintenance, there is a problem that demagnetization cannot be determined because only the magnetic force of the permanent magnet of the motor after maintenance is measured. In addition, there is a problem that a dedicated device is required for measurement and time is required for measurement. In addition, if the magnetic force of the permanent magnet of the motor before maintenance is measured in advance using the method of Patent Document 1, it becomes possible to determine the demagnetization of the permanent magnet accompanying maintenance, but depending on the cause of failure such as coil burnout Inductive voltage may not be measured before maintenance, and cannot be a general determination method for motors after maintenance.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a determination method capable of easily confirming the characteristics of an electric motor using a permanent magnet as a rotor, for example, after maintenance.

A method for determining the characteristics of an electric motor using a permanent magnet for a rotor according to the present invention that meets the above-described object is the characteristics of an electric motor using a permanent magnet as a rotor for connecting the electric motor to a rotational drive source and determining the quality of the electric motor. In the judgment method,
The motor is a three-phase motor, and an analog voltmeter is connected between each phase of U, V, and W to measure a no-load generated voltage of the three-phase motor, and at the time of low-speed rotation of the motor The quality of the permanent magnet of the electric motor is judged based on the movement of the scale needle of the voltmeter.

The motor is connected to a rotational drive source, the no-load generated voltage of the motor and the rotational speed at that time are measured, and compared with a reference value E calculated by an induced voltage calculation formula set in advance in the motor. The quality of the electric motor can also be determined. In this case, the induced voltage calculation formula can be expressed by the following formula.
E = (ke20) × N
(Ke20) = {0.0012 × (θ−20) +1} × (ke)
Here, (ke20) is the induced voltage constant (mV / (rpm)) corrected to 20 ° C., 0.0012 is the temperature coefficient (1 / ° C.), θ is the temperature (° C.) of the yoke of the motor, (ke ) Is an induced voltage constant (mV / (rpm)) set by the electric motor, and N is the rotational speed (rpm) of the electric motor.

In the method for determining the characteristics of an electric motor using a permanent magnet as a rotor, the no-load generated voltage (induced voltage) generated by driving the electric motor with a rotational drive source and the rotational speed at that time are measured, and the measured generated voltage when determining the quality of the motor is compared with a reference value E calculated by the induced voltage calculation equation using the rotational speed was measured to, there is no need to prepare an inverter that matches the capacity of the motor for performing characterization, The determination of the characteristics of motors of various capacities can be performed simply, in a short time and at low cost.
Moreover, since the generated voltage increases in proportion to the rotation speed of the motor, the change in the electric characteristics of the motor can be determined by comparing the change behavior of the generated voltage with respect to the rotation speed and the change behavior of the reference value E with respect to the rotation speed. It can be detected with high accuracy.

Since the predetermined induction voltage calculation formula set in advance is used, the reference value E can be easily calculated if the rotation speed of the motor and the yoke temperature of the motor are known.

In the characterization method of the electric motor using a permanent magnet rotor according to the present invention, there is provided a motor three-phase motors, connected U, V, a voltage meter analog during each phase of the W, the electric motor the movement of the scale needle low velocity revolution of the voltmeter, so determining acceptability of each phase of the permanent magnet motor, the demagnetization occurs in the permanent magnet, Ri a small deflection of the scale needle of the voltmeter Therefore, the pass / fail judgment can be made quickly and easily by visual inspection.

It is explanatory drawing of the determination apparatus with which the characteristic determination method of the electric motor which used the permanent magnet for the rotor which concerns on one embodiment of this invention is applied. It is a graph which shows the relationship between the generated voltage at the time of no load with respect to the rotational speed of an electric motor, and the reference value calculated by an induced voltage calculation formula.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIG. 1, a determination device 10 to which a motor characteristic determination method using a permanent magnet is applied to a rotor according to an embodiment of the present invention performs characteristic determination, and the rotor includes a permanent magnet. Drive means 13 having an induction motor 12 which is an example of a rotational drive source for rotationally driving a three-phase motor 11 which is an example of a motor (permanent magnet synchronous motor), and U, V and W of the three-phase motor 11 It has analog AC voltmeters 14, 15, and 16 that measure voltages between the phases, and a rotation speed meter (not shown) that measures the rotation speed N of the three-phase motor 11.

Here, the drive means 13 includes the induction motor 12 and an inverter 18 that controls the rotation speed of the induction motor 12 by controlling the voltage and frequency of the AC power supply 17. Further, the driving means 13 connects the driving pulley 20 attached to the shaft 19 of the induction motor 12, the driven pulley 22 attached to the shaft 21 of the three-phase motor 11, and the driving pulley 20 and the driven pulley 22. And a power transmission mechanism 24 including a belt 23 that performs the above operation.

Since the induction motor 12 is driven using the inverter 18, the rotational speed of the shaft 19 of the induction motor 12 can be adjusted to an arbitrary value. Thereby, the shaft 21 of the three-phase motor 11 can be stably rotated at the set rotational speed N via the power transmission mechanism 24. As a result, the induced voltage generated in the three-phase motor 11 can be directly measured by the AC voltmeters 14 to 16.

Next, a method for determining the characteristics of an electric motor using a permanent magnet as a rotor according to an embodiment of the present invention will be described.
As shown in FIG. 1, for example, the three-phase motor 11 that has been serviced is attached to a mounting base (not shown) of the determination device 10. Then, the driven pulley 22 is fixed to the shaft 21 of the three-phase motor 11, and the driving pulley 20 and the driven pulley 22 attached to the shaft 19 of the induction motor 12 provided in the determination device 10 are connected via the belt 23. Connect. Further, AC voltmeters 14 to 16 are connected between U, V, and W phases of power terminals (not shown) of the three-phase motor 11.

Next, power is supplied from the AC power supply 17 to the induction motor 12 via the inverter 18 of the determination device 10 to drive the induction motor 12 and rotate the three-phase motor 11. At this time, while adjusting the rotation speed of the induction motor 12 by controlling the frequency of the voltage input from the inverter 18 to the induction motor 12, the rotation speed of the three-phase motor 11 is changed to change the U, A no-load generated voltage (induced voltage) generated between the phases V and W is measured by the voltmeters 14 to 16, and the rotational speed N of the shaft 21 of the three-phase motor 11 is measured by the rotational speed meter.

Here, when the three-phase motor 11 is abnormal, for example, when the demagnetization occurs in the permanent magnet attached to the rotor, when the three-phase motor 11 rotates at a low speed, the demagnetization occurs when the permanent magnet rotates. Corresponding to the change in position, a change appears in the movement of the scale needles of the voltmeters 14 to 16 (a visually observable amplitude of the needle shake occurs periodically), and the quality of the permanent magnet of the three-phase motor 11 can be determined. . Since the abnormality of the three-phase motor 11 is detected from the changing behavior of the scale needles of the voltmeters 14 to 16, the presence or absence of the abnormality can be detected quickly and reliably.
In addition, when it is necessary to specify the permanent magnet in which the demagnetization has occurred, the rotor is pulled out from the three-phase motor 11, and the magnetic force of each permanent magnet provided on the rotor is measured.

The three-phase motor 11 is attached with a test report showing the results when the characteristics of the three-phase motor 11 are measured at the time of shipment. And since the induced voltage constant ke (unit is mV / (rpm)) set at the time of design of the three-phase motor 11 is described in the test report, the rotation speed N (rpm of the shaft 21 of the three-phase motor 11 is described. ) When the temperature (° C.) of the yoke of the three-phase motor 11 is determined, the unloaded generated voltage (induced voltage) of the three-phase motor 11 at that time is obtained as the reference value E calculated by the induced voltage calculation formula. Can do.

Here, the induced voltage calculation formula for calculating the reference value E is E = (ke20) × N, and (ke20) is an induced voltage constant (mV / (rpm)) corrected to 20 ° C. (Ke20) is a temperature coefficient (1 / ° C.) of 0.0012, θ is the temperature (° C.) of the yoke of the three-phase motor 11, and (ke) is an induced voltage constant (mV / () set by the motor. rpm)), using a calculation formula of {0.0012 × (θ−20) +1} × (ke).

Therefore, the generated voltage (induced voltage) between the U, V, and W phases of the three-phase motor 11 measured using the AC voltmeters 14 to 16 and the induced voltage set in the three-phase motor 11 in advance. By comparing with the reference value E, which is the calculated value of the induced voltage calculated by the calculation formula, the induced voltage of the three-phase motor 11 changes with respect to the reference value E (the induced voltage of the three-phase motor 11 at the time of shipment). You can easily see if you are.
If the difference between the induced voltage and the reference value E is within the range of the management standard value of the three-phase motor 11, the three-phase motor 11 is determined to be good, and the difference between the induced voltage and the reference value E is the management standard. If the value is out of the range, the three-phase motor 11 is determined to be defective. Thereby, the characteristic determination of the three-phase motor 11 based on the induced voltage of the three-phase motor 11 can be performed simply, in a short time, and inexpensively.
The management standard value is determined for each three-phase motor 11. For example, when the reference value E indicates the lower limit value of the management standard and the upper limit width is defined with respect to the lower limit value (reference value E) (for example, specified as 5% of the reference value E), the rotation speed N is obtained. A value obtained by adding an upper limit width to the reference value E (lower limit value) is the upper limit value. On the other hand, if the upper and lower limits of the control standard are determined by the change width defined with respect to the reference value E (for example, 5% of the reference value E) with the reference value E as the median value, the rotational speed N The lower limit value is obtained by subtracting the change width from the reference value E (median value) determined from the above, and the upper limit value is obtained by adding the change width to the reference value E (median value). Therefore, if the induced voltage value is within the upper and lower limit range, the three-phase motor 11 is determined to be good. If the induced voltage value is outside the upper and lower limit range, the three-phase motor 11 is defective. It is determined.

When the induced voltage generated between the U-phase and the V-phase of the three-phase motor 11 when the three-phase motor 11 is rotationally driven at a constant rotational speed N is measured with the voltmeter 14, the induced voltage between U and V is The characteristic that increases in proportion to the increase in the rotational speed N is obtained. On the other hand, the reference value E calculated by the induced voltage calculation formula also increases in proportion to the rotational speed N. Therefore, FIG. 2 shows the dependence of the induced voltage between U and V and the reference value E on the rotational speed N in a graph. In FIG. 2, the rotational speed N dependence of the induced voltage between U and V and the rotational speed N dependence of the reference value E show good agreement, and from this, it is determined that the characteristics of the three-phase motor 11 are good. it can.
In addition, since the change behavior of the induced voltage with respect to the rotational speed N is compared with the change behavior of the reference value E with respect to the rotational speed N, it is possible to accurately determine whether or not there is a difference between the induced voltage and the reference value E. The characteristic change of the three-phase motor 11 can be detected with high accuracy.

The three-phase motor determined to be defective is repaired, but is replaced with a new three-phase motor depending on the degree of failure.
On the other hand, for a three-phase motor that is within the control standard value but has been confirmed to change, for example, adjust the output of the inverter that drives the three-phase motor so that the torque initially set for the three-phase motor is obtained. To use.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above-described embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included.
Further, the present invention also includes a combination of components included in the present embodiment and other embodiments and modifications.

10: Determination device, 11: Three-phase motor, 12: Induction motor, 13: Drive means, 14, 15, 16: AC voltmeter, 17: AC power supply, 18: Inverter, 19: Shaft, 20: Drive pulley 21: shaft, 22: driven pulley, 23: belt, 24: power transmission mechanism

Claims (2)

In the method for determining the characteristics of an electric motor using a permanent magnet as a rotor for connecting the electric motor to a rotational drive source and determining whether the electric motor is good or bad ,
The motor is a three-phase motor, and an analog voltmeter is connected between each phase of U, V, and W to measure a no-load generated voltage of the three-phase motor, and at the time of low-speed rotation of the motor A method for determining characteristics of an electric motor using a permanent magnet as a rotor, wherein the quality of the permanent magnet of each phase of the electric motor is determined based on movement of a scale needle of the voltmeter . The method for determining characteristics of an electric motor using a permanent magnet for a rotor according to claim 1, wherein when an abnormality is found in the quality determination, the rotor is pulled out from the three-phase electric motor and provided in the rotor. A method of determining the characteristics of an electric motor using a permanent magnet as a rotor, wherein the permanent magnet is demagnetized by measuring the magnetic force of each permanent magnet .

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