Method for testing characteristics of tested motor, characteristic test device, and computer program

Abstract

To provide a technique for calculating apparent power or a power factor while excluding influences of an induction voltage.SOLUTION: A method includes the steps of: (a) measuring a coil voltage and a coil current of a tested motor in each of M measurement timing over a period of N cycles of the coil voltage, thereby acquiring a voltage measurement value Es[j] and a current measurement value Is[j] in j-th measurement timing; (b) determining that an effective voltage value Er[j] is equal to the voltage measurement value Es[j] in a case where a current index value which is increased / decreased in accordance with the current measurement value Is[j] is equal to or more than a preset determination value; (c) determining that the effective voltage value Er[j] is equal to zero in a case where the current index value is less than the determination value; and (d) calculating apparent power and a power factor of the tested motor from the effective voltage value Er[j], the voltage measurement value Es[j] and the current measurement value Is[j] which are obtained in the M measurement timing.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a method for testing the characteristics of a motor under test, a characteristic testing apparatus, and a computer program.

Background Art

[0002] Patent Document 1 describes a synchronous motor drive device capable of calculating the power factor of a synchronous motor. Generally, the power factor is calculated by dividing the active power by the apparent power. Also, when there is a phase lag in the current, the power factor decreases. Therefore, conventionally, so-called advanced angle control has been adopted to eliminate the phase difference between the voltage and the current. However, simply performing advanced angle control cannot bring the power factor close enough to 1.0, and it was considered that all of the causes were in the third harmonic component. Therefore, measures for the motor drive control circuit have been required to suppress this third harmonic component, but conventionally, the power factor could not be improved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventor of the present disclosure has found that an induced voltage is generated in the electromagnetic coil during the non-excitation period of the motor's electromagnetic coil, and this induced voltage increases the effective voltage value. When the effective voltage value increases due to the induced voltage, the apparent power also increases, so the power factor decreases. For this reason, it has been found that the true apparent power and power factor of the motor could not be measured in the prior art.

Means for Solving the Problems

[0005] The present disclosure has been made to solve at least a part of the above-described problems and can be realized in the following forms.

[0006] According to a first aspect of the present disclosure, there is provided a method for testing the characteristics of a motor under test. The method includes: (a) when N is an integer of 1 or more, M is an integer larger than N, and j is an ordinal number from 1 to M, measuring the coil voltage and coil current of the motor under test at M measurement timings over a period of N cycles of the coil voltage to obtain a voltage measurement value Es[j] and a current measurement value Is[j] at the j-th measurement timing; (b) determining that the effective voltage value Er[j] at the j-th measurement timing is equal to the voltage measurement value Es[j] when a current index value that increases or decreases according to the current measurement value Is[j] is equal to or greater than a preset determination value; (c) determining that the effective voltage value Er[j] is equal to zero when the current index value is less than the determination value; and (d) calculating the apparent power and power factor of the motor under test from the effective voltage value Er[j], the voltage measurement value Es[j], and the current measurement value Is[j] obtained at the M measurement timings. According to this method, it is possible to calculate accurate apparent power and power factor by eliminating the influence of the induced voltage.

[0007] According to a second aspect of the present disclosure, there is provided a characteristic test apparatus for testing the characteristics of a motor under test. When N is an integer of 1 or more, M is an integer larger than N, and j is an ordinal number from 1 to M, the characteristic test apparatus measures the coil voltage and coil current of the motor under test at M measurement timings over a period of N cycles of the coil voltage, thereby obtaining a voltage measurement value Es[j] and a current measurement value Is[j] at the j-th measurement timing. The characteristic test apparatus includes a measurement value acquisition unit and a characteristic calculation unit that calculates the characteristics of the motor under test using the voltage measurement value Es[j] and the current measurement value Is[j]. When a current index value that increases or decreases according to the current measurement value Is[j] is equal to or greater than a preset determination value, the characteristic calculation unit determines that the effective voltage value Er[j] at the j-th measurement timing is equal to the voltage measurement value Es[j]. When the current index value is less than the determination value, the characteristic calculation unit determines that the effective voltage value Er[j] is equal to zero. The characteristic calculation unit is configured to execute a process of calculating the apparent power and power factor of the motor under test from the effective voltage value Er[j], the voltage measurement value Es[j], and the current measurement value Is[j] obtained at the M measurement timings. According to this characteristic test apparatus, it is possible to calculate accurate apparent power and power factor by eliminating the influence of the induced voltage.

[0008] According to a second aspect of the present disclosure, there is provided a computer program for executing a process of testing characteristics of a motor under test. This computer program causes a computer to execute: (a) when N is an integer of 1 or more, M is an integer larger than N, and j is an ordinal number from 1 to M, measuring the coil voltage and coil current of the motor under test at M measurement timings over a period of N cycles of the coil voltage, thereby obtaining a voltage measurement value Es[j] and a current measurement value Is[j] at the j-th measurement timing; (b) when a current index value that increases or decreases according to the current measurement value Is[j] is equal to or greater than a preset determination value, determining that an effective voltage value Er[j] at the j-th measurement timing is equal to the voltage measurement value Es[j]; (c) when the current index value is less than the determination value, determining that the effective voltage value Er[j] is equal to zero; and (d) calculating apparent power and power factor of the motor under test from the effective voltage value Er[j], the voltage measurement value Es[j], and the current measurement value Is[j] obtained at the M measurement timings. According to this computer program, the influence of the induced voltage can be eliminated, and accurate apparent power and power factor can be calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0010] FIG. 1 is a block diagram showing the configuration of a motor test system according to an embodiment. This motor test system includes a motor under test 100, a motor test apparatus 200, and a characteristic test apparatus 300.

[0011] As the motor under test 100, any type of motor having an arbitrary number of phases can be used. However, the motor under test 100 preferably uses a permanent magnet rotor to generate an induced voltage and is a high torque type brushless motor with a small inductance (few turns) of the phase coil, and more preferably a coreless motor without an iron core and with a small inductance.

[0012] The motor under test 100 is electrically connected to a drive circuit 120. A DC input voltage Ev is supplied to the drive circuit 120 from a constant voltage power supply 130. The voltage value of the input voltage Ev can be adjusted by the characteristic test apparatus 300. The drive circuit 120 is, for example, a motor driver configured as an H-bridge circuit, and the transistors in the drive circuit 120 turn on / off in response to a control signal Sd supplied from the characteristic test apparatus 300. The control signal Sd is, for example, a signal for performing PWM control of the motor under test 100. In PWM control, the rotational position of the motor under test 100 is detected according to the output of a magnetic sensor 104, and the control signal Sd for each phase is generated according to this rotational position. A current meter 151 for measuring the coil current of the electromagnetic coil and a voltmeter 161 for measuring the coil voltage of the electromagnetic coil are provided in the wiring between the drive circuit 120 and the motor under test 100.

[0013] The motor test apparatus 200 includes a first coupling 211, a torque meter 220, a second coupling 212, an electric brake 230, an AC / DC conversion unit 240, a DC load unit 250, and a measurement value collection unit 260. The mechanical connection structure including the first coupling 211, the torque meter 220, the second coupling 212, and the electric brake 230 is referred to as a test connection structure 270.

[0014] The rotating shaft 110 of the test motor 100 and the first rotating shaft 221 of the torque meter 220 are connected by a first coupling 211. The torque meter 220 has a first rotating shaft 221 and a second rotating shaft 222, and measures the torque T between the first rotating shaft 221 and the second rotating shaft 222. Preferably, the torque meter 220 is further configured to be able to measure the rotational speed Nm of the rotating shafts 221, 222. Instead of measuring the rotational speed Nm with the torque meter 220, the rotational speed Nm may be accurately measured by the clock counter value within the sensor signal using the magnetic sensor 104 provided in the test motor 100. The second rotating shaft 222 of the torque meter 220 and the rotating shaft 232 of the electric brake 230 are connected by a second coupling 212. The electric brake 230 has a coreless motor structure with low iron loss (cogging loss, hysteresis loss, etc.). The electric brake 230 is preferably configured as a two-phase or three-phase brushless motor, for example. In the present embodiment, the electric brake 230 has a magnetic sensor 234 for measuring the rotational position of the rotor. In the present embodiment, the magnetic sensor 234 is a sensor that is fixed to the stator and measures the magnetic flux density of the permanent magnet provided on the rotor. The magnetic sensor 234 is constituted by, for example, a Hall IC. However, the magnetic sensor 234 can be omitted.

[0015] The AC / DC conversion unit 240 is electrically connected to a plurality of phases of coils of the electric brake 230, and full-wave rectifies the alternating current induced voltage Vi generated in the coils to convert it into a direct current voltage Vd. The DC load unit 250 is electrically connected to the AC / DC conversion unit 240 and consumes the power by the direct current voltage Vd.

[0016] The measurement value collection unit 260 collects the measured value Es of the coil voltage measured by the voltmeter 161, the measured value Is of the coil current measured by the ammeter 151, the torque T and the rotational speed Nm measured by the torque meter 220 in synchronization with the control signal Sd of the drive circuit 120, and transfers them to the characteristic test device 300.

[0017] The characteristic test device 300 includes a measurement value acquisition unit 310, a characteristic calculation unit 320, and a characteristic display unit 330. Also, the characteristic test device 300 has a function of controlling each part of the motor test device 200. The measurement value acquisition unit 310 acquires measurement values including the measured values Es and Is of the coil voltage and coil current of the motor under test 100 from the measurement value collection unit 260. The characteristic calculation unit 320 calculates the characteristics of the motor under test 100 using the measured values Es and Is of the coil voltage and coil current. The characteristic display unit 330 displays the calculated characteristics of the motor under test 100 on the display screen. In this embodiment, the characteristic calculation unit 320 calculates the apparent power and power factor of the motor under test 100. The characteristic test device 300 can be realized by, for example, a personal computer. The functions of the characteristic test device 300 are realized by the processor executing a computer program stored in the memory of the characteristic test device 300.

[0018] FIG. 2 is a graph showing the drive waveform of the motor under test 100 and the voltage measurement value Es[j] and current measurement value Is[j]. In this embodiment, the motor under test 100 is a two-phase brushless motor and is PWM controlled. The phase A voltage Va and phase B voltage Vb shown at the top of FIG. 2 represent the ideal analog voltage waveforms of the two-phase electromagnetic coils. The voltage waveforms of the phase A voltage Va and phase B voltage Vb change periodically every one cycle Pw. One cycle Pw corresponds to 360 degrees of electrical angle. The phase A voltage Vapwm by PWM control becomes the rectangular wave shown third from the top in FIG. 2. The phase A voltage Vapwm shown fourth from the top in FIG. 2 is an enlarged view of a part. The dashed-dotted line indicates the measurement timing j, that is, the sampling timing.

[0019] The two graphs at the bottom of FIG. 2 show an enlarged view of the voltage measurement value Es[j] and current measurement value Is[j] measured during one period Pe of the rectangular wave of PWM control. The voltage measurement value Es[j] and current measurement value Is[j] are the values measured at the measurement timing j indicated by the dashed-dotted line.

[0020] The period Pe of one cycle of the PWM-controlled rectangular wave can be divided into three periods P1 to P3. The first period P1 is the PWM driving period of the coil. In this first period P1, the measured voltage value Es[j] becomes a positive value, and the measured current value Is[j] gradually increases, and electrical energy is accumulated in the phase A coil. The second period P2 is the discharge period of the coil. In this second period P2, the measured voltage value Es[j] becomes a negative value, and the measured current value Is[j] gradually decreases, and the electrical energy accumulated in the phase A coil is discharged.

[0021] The third period P3 is the period during which the induced voltage Ed generated in the electromagnetic coil due to the rotation of the rotor is detected during the off period of the PWM control. In this third period P3, since the induced voltage Ed corresponding to the rotational speed of the rotor appears, the measured voltage value Es[j] becomes a non-zero value, and the measured current value Is[j] is almost zero. The waveform of the induced voltage Ed has a sine wave shape that changes according to the positional relationship between the electromagnetic coil and the permanent magnet, and the changes in the induced voltage Ed in the first period P1 and the second period P2 are drawn with dotted lines. Thus, although the induced voltage Ed corresponding to the rotation of the rotor is generated also in the first period P1 and the second period P2, the driving voltage is larger than the induced voltage Ed, and a coil current is generated due to the potential difference (driving voltage - induced voltage Ed), and the induced voltage Ed is hidden by that potential difference. Therefore, the induced voltage Ed cannot be clearly recognized in the first period P1 and the second period P2.

[0022] FIG. 3 is a diagram showing the operating states of the drive circuit 120 in the three periods P1 to P3 of FIG. 2. The drive circuit 120 includes an H-bridge circuit composed of four transistors Qt1, Qb1, Qt2, and Qb2 that drive the A-phase coil 101. Control signals St1, Sb1, St2, and Sb2 are respectively input to the gate electrodes of the four transistors Qt1, Qb1, Qt2, and Qb2. When driving the A-phase coil 101 in the first period P1, two transistors Qb1 and Qt2 are turned on, and the other two transistors Qt1 and Qb2 are turned off. In this state, current flows through the A-phase coil 101 along the path including the two transistors Qb1 and Qt2 as indicated by the dashed line. The voltage level of the rectangular pulse voltage is approximately the same as the input voltage Ev supplied from the constant voltage power supply 130.

[0023] In the second period P2, the transistor Qt2 is switched from on to off. In this state, as indicated by the dashed line, current flows through the A-phase coil 101 along the path including the flywheel diode of the transistor Qt2 and the transistor Qb1. Note that although the example of FIG. 3 shows the discharge period on the ground side low side, a discharge period can be provided similarly on the power supply side high side.

[0024] In the third period P3, the on / off states of the transistors Qt1, Qb1, Qt2, and Qb2 are the same as those in the second period P2. In this state, the discharge from the A-phase coil 101 is completed, and the induced voltage Ed due to the rotation of the rotor is generated in the A-phase coil 101, but the current is almost zero.

[0025] The active power P of each phase of the motor under test 100 is calculated as follows using the voltage measurement value Es[j] and the current measurement value Is[j] shown in FIG. 2. P = Km·SQRT{ΣPe[j]^2 / M} …(q1) Pe[j] = Es[j]×Is[j] …(q2) Here, Km is a coefficient determined according to the coil structure of the motor under test 100, SQRT{} represents the operation of obtaining the square root of the expression inside the parentheses, Σ represents the operation of adding from 1 to M for j, and "^2" represents the operation of squaring. The coefficient Km is a conversion coefficient for converting line power to phase power. When n is an integer of 2 or more, in the case of an n-phase motor in which each phase is composed of independent coils, Km is 1.0. In the case of a three-phase motor, in the star connection, it is necessary to convert the phase voltage = line voltage / √3, and in the delta connection, it is necessary to convert the phase current = line current / √3. Therefore, in a three-phase motor with a star connection or a delta connection, when calculating the power for one phase using the line voltage and the line current, Km = 1 / √3.

[0026] However, also for a three-phase motor with a star connection or a delta connection, when calculating the power for one phase using the phase voltage and the phase current, the coefficient Km in the above equation (q1) is 1.0. Considering this point, when calculating the power for one phase using the phase voltage and the phase current, regardless of the coil structure of the motor under test 100, Km = 1.0. Therefore, in the present embodiment, it is assumed that Km = 1.0 is used regardless of the coil structure.

[0027] In this way, the active power P can be calculated by multiplying the voltage measurement value Es[j] and the current measurement value Is[j] to obtain the active power value Pe[j], and then obtaining the root mean square of the squares of the active power values Pe[j] obtained at M measurement timings, SQRT{ΣPe[j]^2 / M}.

[0028] The apparent power Sc of the motor under test 100 is calculated as follows for each phase as one phase. Sc = Km·Es_rms·Is_rms …(q3) Es_rms = SQRT(ΣEs[j]^2 / M) …(q4) Is_rms = SQRT(ΣIs[j]^2 / M) …(q5) Thus, the apparent power Sc can be calculated by multiplying the root mean square Es_rms of the voltage measurement values Es[j] obtained at M measurement timings j by the root mean square Is_rms of the current measurement values Is[j] obtained at the M measurement timings j.

[0029] The power factor ηc is calculated by dividing the active power P by the apparent power Sc as follows. ηc = P / Sc …(q6)

[0030] In the third period P3 shown in FIG. 2, since the induced voltage Ed appears, the voltage measurement value Es[j] is not zero, and the current measurement value Is[j] is almost zero. In this case, the active power P given by equations (q1) and (q2) is not affected by the induced voltage Ed in the third period P3 because the current measurement value Is[j] is almost zero. On the other hand, the apparent power Sc given by equations (q3) to (q5) includes a component of the square of the voltage measurement value Es[j]. Therefore, even if the current measurement value Is[j] is zero, it is affected by the induced voltage Ed in the third period P3 and increases. Also, when the apparent power Sc increases, the power factor ηc decreases.

[0031] Thus, when calculating the apparent power Sc and the power factor ηc according to the conventional calculation method, the apparent power Sc increases and the power factor ηc decreases under the influence of the induced voltage Ed in the third period P3. However, since the induced voltage Ed in the third period P3 is independent of the driving power, it should originally be excluded from the calculation of the apparent power and the power factor. Therefore, in the present embodiment, the accurate values of the apparent power and the power factor are calculated by excluding the induced voltage Ed in the third period P3 from the effective voltage value for calculating the apparent power.

[0032] The apparent power Sc and the power factor ηc calculated by the above equations (q3) to (q6) are values calculated according to the conventional calculation method, so they are called "conventional apparent power Sc" and "conventional power factor ηc". The method for calculating the apparent power and the power factor according to the present disclosure will be described later. On the other hand, the active power P calculated by the above equations (q1) and (q2) is not affected by the induced voltage in the third period P3, so it is used as it is in the calculation method of the present disclosure.

[0033] Conventionally, it was considered that the reason why the power factor did not become sufficiently high even when the advance angle control was performed was due to the third harmonic component generated along with the rectangular wave of the PWM control. However, since the third harmonic component is a high-frequency vibration waveform superimposed on the rectangular drive waveform, it is unlikely to have a significant impact on the apparent power and the active power. Therefore, it is presumed that the main reason why the power factor did not increase in the conventional technology was due to the induced voltage Ed in the third period P3.

[0034] Also, conventionally, the third period P3 has not been fully recognized. The reason for this is presumably that conventional motors have a coreless motor structure and a specification with a large number of turns, so the inductance and resistance values are large, and the first period P1 and the second period P2 are dominant without the occurrence of the third period P3. In recent years, for electric motor utilization technologies such as electric vehicles, drones, and aircraft, high torque performance has been required for motors. In order to meet this requirement, if a coreless structure or a coil specification with a small number of turns is adopted, the inductance and resistance values become very small, the second period P2 becomes short, the third period P3 appears, and the importance of the third period P3 increases. This can be said to be a new problem that has arisen with the improvement of motor characteristics corresponding to the times.

[0035] The present disclosure is applicable not only to two-phase motors but also to three-phase motors. In this embodiment, even in the case of a three-phase motor, power and power factor are calculated using phase voltage and phase current, similar to a two-phase motor. In the present disclosure, regardless of the number of phases of the motor, the phase voltage of one phase of the coil is referred to as "coil voltage". Also, the phase current of one phase of the coil is referred to as "coil current". Further, the present disclosure is applicable not only to PWM control but also to motors that operate according to control other than PWM control, such as 120-degree conduction control of a three-phase motor.

[0036] Note that in a three-phase motor, the active power Wp of each phase and the three-phase active power W in star connection and delta connection can be calculated according to the following equations, respectively. Wp = 1 / √3·V L ·I L ·cosθ …(q7) W = 3·Wp = √3·V L ·I L ·cosθ …(q8) Here, V L is the line-to-line voltage, and I L is the line current. When calculating power using the line-to-line voltage V L and the line current I L , the coefficient Km in the above-mentioned equations (q1) and (q3) is 1 / √3 on the right side of equation (q7). However, in this embodiment, since the power of one phase is calculated using the phase voltage and phase current even in the case of a three-phase motor, Km = 1.0.

[0037] Figure 4 is a flowchart showing the procedure of the characteristic test of the motor under test 100. This characteristic test is preferably executed with the motor under test 100 rotating at a constant rotational speed Nm and a constant torque T.

[0038] In the process of Figure 4, the following parameters are used. · N: The number of periods Pw of the coil voltage for measuring the coil voltage and the coil current, which is an integer of 1 or more. · M: The total number of measurement timings of the coil voltage and the coil current, which is an integer larger than N. · j: An ordinal number indicating the measurement timing, which is an integer from 1 to M. · Es[j]: The voltage measurement value of the coil voltage measured at the measurement timing j. · Is[j]: The current measurement value of the coil current measured at the measurement timing j. · Ix[j]: A current index value that increases or decreases according to the current measurement value Is[j]. · Ixmin: The determination value of the current index value Ix[j]. · Er[j]: The effective voltage value. · Ei[j]: The induced voltage value. · S: The apparent power excluding the induced voltage in the third period P3. · P: The active power. · η: The power factor calculated using the apparent power S. · Sc: The conventional apparent power calculated by the conventional calculation method. · ηc: The conventional power factor calculated using the conventional apparent power Sc.

[0039] In step S10, the measurement timing j is set to 1, and also, the above-described various parameters are initialized. In this embodiment, the number of periods N of the coil voltage for measuring the coil voltage and the coil current is assumed to be equal to 1.

[0040] In step S11, the measurement value acquisition unit 310 acquires the voltage measurement value Es[j] and the current measurement value Is[j] measured at the measurement timing j.

[0041] In step S12, the measurement value acquisition unit 310 calculates a current index value Ix[j] that increases or decreases according to the current measurement value Is[j]. The current index value Ix[j] can be calculated, for example, using either of the following equations (q9) and (q10). Ix[j] = ABS(Is[j]) …(q9) Ix[j] = ABS(Es[j]·Is[j]) …(q10) Here, ABS() is an operation for taking the absolute value of the expression inside the parentheses.

[0042] The current index value Ix[j] given by the above equation (q9) is the absolute value of the current measurement value Is[j]. The current index value Ix[j] given by the above equation (q10) is the absolute value of the product of the voltage measurement value Es[j] and the current measurement value Is[j], that is, the absolute value of the power measurement value. The current index values Ix[j] given by equations (q9) and (q10) are both proportional to the absolute value of the current measurement value Is[j]. However, the current index value Ix[j] may be calculated using an equation other than equations (q9) and (q10). In this embodiment, the current index value Ix[j] is calculated using equation (q9).

[0043] In step S13, the characteristic calculation unit 320 compares the current index value Ix[j] with a preset determination value Ixmin. If Ixmin ≦ Ix[j], the process proceeds to step S14, and it is determined that the effective voltage value Er[j] is equal to the voltage measurement value Es[j]. Also, the induced voltage value Ei[j] is determined to be equal to zero. The process of this step S14 corresponds to the process of using the voltage measurement value Es[j] obtained in the first period P1 and the second period P2 shown in FIG. 2 as the effective voltage value Er[j]. Note that the current measurement value Is[j] is used as the effective current value as it is.

[0044] On the other hand, if Ix[j] < Ixmin, the process proceeds to step S15, and it is determined that the effective voltage value Er[j] is equal to zero. Also, the induced voltage value Ei[j] is determined to be equal to the voltage measurement value Es[j]. The process of this step S15 is a process of determining that the voltage measurement value Es[j] obtained in the third period P3 shown in FIG. 2 is the induced voltage. Note that the current measurement value Is[j] is used as the effective current value as it is.

[0045] In step S16, it is determined whether the measurement timing j has reached the maximum value M. If j is smaller than M, the process proceeds to step S17, j is incremented by 1, and the process returns to step S11, and the above-described steps S11 to S16 are executed again. If j has reached M, the process proceeds to step S18.

[0046] In step S18, the characteristic calculation unit 320 determines whether to calculate and display the characteristics while excluding the induced voltage. Whether to exclude the induced voltage is specified by the user. If the induced voltage is to be excluded, the process of step S19 is executed; if the induced voltage is not to be excluded, the process of step S20 is executed.

[0047] In step S19, the characteristic calculation unit 320 calculates the active power P, apparent power S, and power factor η of the motor under test 100 using the effective voltage value Er[j], voltage measurement value Es[j], and current measurement value Is[j]. The active power P is calculated according to the following formula. P = Km·SQRT{ΣPe[j]^2 / M} …(q11) Pe[j] = Es[j]×Is[j] …(q12) These are the same formulas as the above-mentioned (q1) and (q2). That is, the active power P can be calculated by multiplying the voltage measurement value Es[j] and current measurement value Is[j] obtained at the measurement timing j to obtain the active power value Pe[j], and then obtaining the square root of the mean square SQRT{ΣPe[j]^2 / M} of the active power values Pe[j] obtained at M measurement timings.

[0048] The apparent power S is calculated according to the following formula. S = Km·Er_rms·Is_rms …(q13) Er_rms = SQRT(ΣEr[j]^2 / M) …(q14) Is_rms = SQRT(ΣIs[j]^2 / M) …(q15) In this way, the apparent power S can be calculated by multiplying the square root of the mean square Er_rms of the effective voltage values Er[j] obtained at M measurement timings j and the square root of the mean square Is_rms of the current measurement values Is[j] obtained at M measurement timings j.

[0049] The power factor η is calculated by dividing the active power P by the apparent power S, as shown in the following formula. η = P / S …(q16)

[0050] In step S20, the characteristic calculation unit 320 calculates the active power P, the conventional apparent power Sc, and the conventional power factor ηc of the motor under test 100. These characteristics are calculated according to the above-described equations (q1) to (q6).

[0051] In step S21, the characteristic display unit 330 displays the characteristics of the motor under test 100 calculated on the display device of the characteristic test apparatus 300.

[0052] FIG. 5 is an explanatory diagram showing an example of a display screen of the characteristics of the motor under test 100. Here, a first display screen W1 for displaying the apparent power S and the power factor η calculated by excluding the induced voltage, and a second display screen W2 for displaying the conventional apparent power Sc and the conventional power factor ηc are illustrated.

[0053] The first display screen W1 has a mode designation tool MT for designating whether or not to exclude the induced voltage, and a determination value setting tool IT for setting the determination value Ixmin for excluding the induced voltage. The user can use the mode designation tool MT to display the motor characteristics including the apparent power S and the power factor η calculated by excluding the induced voltage in a first mode, and the conventional motor characteristics including the conventional apparent power Sc and the conventional power factor ηc in a second mode. The characteristics of the motor under test 100 can be displayed in either mode.

[0054] On the first display screen W1, the elimination of the induced voltage is set to "ON", and it is specified to calculate and display the apparent power S and the power factor η according to the above equations (q11) to (q16). Also, the determination value Ixmin of the current index value Ix[j] for determining whether or not to eliminate the induced voltage at each individual measurement timing j is set to 1.2 mA. The determination value Ixmin is preferably set to a value greater than 0, and is set in consideration of the measuring instrument accuracy and the measuring instrument S / N ratio according to the current capacity of the motor. For example, in the case of a very small motor such as a vibration motor of a mobile phone, it is preferable to set the determination value Ixmin to several mA. Also, in the case of a large motor such as a drive motor of an electric vehicle, it is preferable to set the determination value Ixmin to several A.

[0055] In the example of the first display screen W1, the root mean square value Er_rms of the effective voltage, the root mean square value Is_rms of the effective current, the root mean square value Ei_rms of the induced voltage, the apparent power S, the active power P, and the power factor η are displayed. In this example, the power factor η is 1.0.

[0056] The second display screen W2 shows the calculation results when the elimination of the induced voltage is set to "OFF". That is, it is an example of the result of calculating the conventional apparent power Sc and the conventional power factor ηc according to the above equations (q1) to (q6). In this example, the conventional power factor ηc is 0.83.

[0057] As can be understood by comparing the test results shown on the two display screens W1 and W2, the apparent power S calculated by eliminating the induced voltage is a smaller value than the conventional apparent power Sc. Also, the power factor η calculated by eliminating the induced voltage is a larger value than the conventional power factor ηc. Since these are values calculated by eliminating the induced voltage that is irrelevant to the drive power, it is possible to consider that they show more accurate values as the characteristics of the test motor 100.

[0058] Incidentally, the apparent power S and power factor η calculated by eliminating the induced voltage, and the conventional apparent power Sc and conventional power factor ηc may be displayed on the same display screen. Also, together with the apparent power and power factor, the values of the rotational speed Nm and torque T of the motor under test 100 may be displayed.

[0059] In the above-described embodiment, when the current index value Ix[j] that increases or decreases according to the measured current value Is[j] is equal to or greater than the determination value Ixmin, the effective voltage value Er[j] is determined to be equal to the measured voltage value Es[j], and when the current index value Ix[j] is less than the determination value Ixmin, the effective voltage value Er[j] is determined to be equal to zero. Therefore, it is possible to calculate the accurate apparent power and power factor by eliminating the influence of the induced power. Also, by referring to the accurate power factor, it is possible to easily determine whether the advance angle control of the motor under test 100 is appropriate. Furthermore, in the heat generation problem, which is the final stage of motor evaluation, copper loss is greatly involved, and when the heat generation amount due to copper loss is Pc = R·(I·cosθ)^2 and the power factor (cosθ) has a great influence, it is also possible to make an appropriate technical judgment.

[0060] Incidentally, the processing procedure of FIG. 4 may be changed as appropriate. In particular, for the purpose of saving memory capacity and improving calculation speed, the calculation methods and calculation orders of various values may be devised. Also, the content of the present disclosure can be applied when calculating the apparent power and power factor with a measuring instrument such as an oscilloscope. In this case, it is preferable to set the operations according to the above-described equations (q1) to (q6) and (q11) to (q16) in the measuring instrument.

[0061] The present disclosure is not limited to the above-described embodiments, embodiments, and modification examples, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, embodiments, and modification examples corresponding to the technical features in each form described in the summary of the disclosure can be appropriately replaced or combined in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Also, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

[0062] (1) According to a first aspect of the present disclosure, a method for testing the characteristics of a motor under test is provided. The method includes: (a) when N is an integer of 1 or more, M is an integer greater than N, and j is an ordinal number from 1 to M, measuring the coil voltage and coil current of the motor under test at M measurement timings over a period of N periods of the coil voltage, thereby obtaining a voltage measurement value Es[j] and a current measurement value Is[j] at the j-th measurement timing; (b) when a current index value that increases or decreases according to the current measurement value Is[j] is equal to or greater than a preset determination value, determining that an effective voltage value Er[j] at the j-th measurement timing is equal to the voltage measurement value Es[j]; (c) when the current index value is less than the determination value, determining that the effective voltage value Er[j] is equal to zero; and (d) calculating an apparent power and a power factor of the motor under test from the effective voltage value Er[j], the voltage measurement value Es[j], and the current measurement value Is[j] obtained at the M measurement timings. According to this method, it is possible to calculate accurate apparent power and power factor by eliminating the influence of the induced voltage.

[0063] (2) In the above method, the step (b) may include a step of determining that an induced voltage value Ei[j] at the j-th measurement timing is equal to zero when the current index value is equal to or greater than the determination value, and the step (c) may include a step of determining that the induced voltage value Ei[j] is equal to the voltage measurement value Es[j] when the current index value is less than the determination value. According to this method, the induced voltage value can be calculated.

[0064] (3) In the above method, the step (d) may include: (d1) a step of calculating the apparent power by multiplying the root mean square of the effective voltage value Er[j] obtained at the M measurement timings by the root mean square of the current measurement value Is[j] obtained at the M measurement timings; (d2) a step of obtaining the active power value Pe[j] by multiplying the voltage measurement value Es[j] by the current measurement value Is[j], and calculating the active power by obtaining the root mean square of the active power values Pe[j] obtained at the M measurement timings; and (d3) a step of calculating the power factor by dividing the active power by the apparent power. According to this method, the apparent power, the active power, and the power factor can be calculated by simple calculations.

[0065] (4) The above method may further include: a step of calculating the conventional apparent power by multiplying the root mean square of the voltage measurement value Es[j] obtained at the M measurement timings by the root mean square of the current measurement value Is[j] obtained at the M measurement timings; and a step of calculating the conventional power factor by dividing the active power by the conventional apparent power. According to this method, the conventional apparent power and the conventional power factor calculated by the conventional method can be calculated.

[0066] (5) According to a second aspect of the present disclosure, there is provided a characteristic test apparatus for testing the characteristics of a motor under test. When N is an integer of 1 or more, M is an integer larger than N, and j is an ordinal number from 1 to M, this characteristic test apparatus measures the coil voltage and coil current of the motor under test at M measurement timings over a period of N cycles of the coil voltage, thereby obtaining a voltage measurement value Es[j] and a current measurement value Is[j] at the j-th measurement timing. The characteristic test apparatus includes a measurement value acquisition unit and a characteristic calculation unit that calculates the characteristics of the motor under test using the voltage measurement value Es[j] and the current measurement value Is[j]. When a current index value that increases or decreases according to the current measurement value Is[j] is equal to or greater than a preset determination value, the characteristic calculation unit determines that the effective voltage value Er[j] at the j-th measurement timing is equal to the voltage measurement value Es[j]. When the current index value is less than the determination value, the characteristic calculation unit determines that the effective voltage value Er[j] is equal to zero. The characteristic calculation unit is configured to execute a process of calculating the apparent power and power factor of the motor under test from the effective voltage value Er[j], the voltage measurement value Es[j], and the current measurement value Is[j] obtained at the M measurement timings. According to this characteristic test apparatus, it is possible to calculate accurate apparent power and power factor by eliminating the influence of the induced voltage.

[0067] (6) The above characteristic test apparatus may further include a characteristic display unit that displays the characteristics of the motor under test calculated by the characteristic calculation unit on a display screen. The characteristic display unit may display on the display screen a mode designation tool for designating either a first mode in which the apparent power and the power factor are displayed or a second mode in which a conventional apparent power and a conventional power factor calculated by a conventional method are displayed. According to this characteristic test apparatus, it is possible to display either the apparent power and power factor without the influence of the induced voltage or the conventional apparent power and conventional power factor without eliminating the influence of the induced voltage according to the designation of the user.

[0068] (7) In the above characteristic test apparatus, the characteristic display unit may further display, on the display screen, a determination value setting tool for setting the determination value. According to this characteristic test apparatus, a user can arbitrarily set a determination value.

[0069] (8) According to the second aspect of the present disclosure, there is provided a computer program for executing a process of testing the characteristics of a motor under test. This computer program causes a computer to execute: (a) a process of obtaining a voltage measurement value Es[j] and a current measurement value Is[j] at the j-th measurement timing by measuring the coil voltage and the coil current of the motor under test at M measurement timings over a period of N cycles of the coil voltage, where N is an integer of 1 or more, M is an integer greater than N, and j is an ordinal number from 1 to M; (b) a process of determining that the effective voltage value Er[j] at the j-th measurement timing is equal to the voltage measurement value Es[j] when a current index value that increases or decreases according to the current measurement value Is[j] is equal to or greater than a preset determination value; (c) a process of determining that the effective voltage value Er[j] is equal to zero when the current index value is less than the determination value; and (d) a process of calculating the apparent power and the power factor of the motor under test from the effective voltage value Er[j], the voltage measurement value Es[j], and the current measurement value Is[j] obtained at the M measurement timings. According to this computer program, it is possible to calculate accurate apparent power and power factor by eliminating the influence of the induced voltage.

Description of Signs

[0070] 100…Motor under test, 101…Phase A coil, 104…Magnetic sensor, 110…Rotating shaft, 120…Drive circuit, 130…Constant voltage power supply, 151…Ammeter, 161…Voltmeter, 200…Motor test device, 211…First coupling, 212…Second coupling, 220…Torque meter, 221…First rotating shaft, 222…Second rotating shaft, 230…Electrical brake, 232…Rotating shaft, 234…Magnetic sensor, 240…AC / DC conversion unit, 250…DC load unit, 260…Measured value collection unit, 270…Test connection structure, 300…Characteristic test device, 310…Measured value acquisition unit, 320…Characteristic calculation unit, 330…Characteristic display unit

Claims

1. A method for testing the characteristics of a motor under test, comprising: (a) When N is an integer of 1 or more, M is an integer larger than N, and j is an ordinal number from 1 to M, by measuring the coil voltage and coil current of the motor under test at M measurement timings over a period of N cycles of the coil voltage, obtaining a voltage measurement value Es[j] and a current measurement value Is[j] at the j-th measurement timing; (b) When a current index value that increases or decreases according to the current measurement value Is[j] is equal to or greater than a preset determination value, determining that an effective voltage value Er[j] at the j-th measurement timing is equal to the voltage measurement value Es[j]; (c) When the current index value is less than the determination value, determining that the effective voltage value Er[j] is equal to zero; (d) Calculating the apparent power and power factor of the motor under test from the effective voltage value Er[j], the voltage measurement value Es[j], and the current measurement value Is[j] obtained at the M measurement timings. A method including the above steps.

2. The method according to Claim 1, wherein: step (b) includes, when the current index value is equal to or greater than the determination value, determining that an induced voltage value Ei[j] at the j-th measurement timing is equal to zero; step (c) includes, when the current index value is less than the determination value, determining that the induced voltage value Ei[j] is equal to the voltage measurement value Es[j].

3. The method according to Claim 1, wherein: step (d) includes: (d1) calculating the apparent power by multiplying the root mean square of the squares of the effective voltage values Er[j] obtained at the M measurement timings by the root mean square of the squares of the current measurement values Is[j] obtained at the M measurement timings; (d2) calculating the active power by multiplying the voltage measurement value Es[j] by the current measurement value Is[j] to obtain an active power value Pe[j], and then obtaining the root mean square of the squares of the active power values Pe[j] obtained at the M measurement timings; (d3) calculating the power factor by dividing the active power by the apparent power. A method including the above steps.

4. The method according to Claim 3, further comprising: A step of calculating the apparent power in a conventional manner by multiplying the root mean square of the voltage measurement values Es[j] obtained at the M measurement timings by the root mean square of the current measurement values Is[j] obtained at the M measurement timings; A step of calculating the conventional power factor by dividing the active power by the conventional apparent power; A method comprising the above.

5. A characteristic test apparatus for testing the characteristics of a motor under test, When N is an integer of 1 or more, M is an integer larger than N, and j is an ordinal number from 1 to M, the coil voltage and coil current of the motor under test are measured at M measurement timings over a period of N cycles of the coil voltage, respectively, so as to obtain a voltage measurement value Es[j] and a current measurement value Is[j] at the j-th measurement timing, a measurement value acquisition unit; A characteristic calculation unit that calculates the characteristics of the motor under test using the voltage measurement value Es[j] and the current measurement value Is[j]; Comprising: The characteristic calculation unit When the current index value that increases or decreases according to the current measurement value Is[j] is equal to or greater than a preset determination value, a process of determining that the effective voltage value Er[j] at the j-th measurement timing is equal to the voltage measurement value Es[j]; When the current index value is less than the determination value, a process of determining that the effective voltage value Er[j] is equal to zero; A process of calculating the apparent power and power factor of the motor under test from the effective voltage value Er[j], the voltage measurement value Es[j], and the current measurement value Is[j] obtained at the M measurement timings; A characteristic test apparatus configured to execute the above.

6. The characteristic test apparatus according to claim 5, further comprising A characteristic display unit that displays the characteristics of the motor under test calculated by the characteristic calculation unit on a display screen, The characteristic display unit displays a mode designation tool on the display screen for designating either a first mode of displaying the apparent power and the power factor or a second mode of displaying the conventional apparent power and the conventional power factor calculated by a conventional method. A characteristic test apparatus.

7. The characteristic test apparatus according to claim 6, The characteristic display unit further displays a determination value setting tool for setting the determination value on the display screen. A characteristic test apparatus.

8. A computer program for executing a process of testing the characteristics of a motor under test, When N is an integer of 1 or more, M is an integer larger than N, and j is an ordinal number from 1 to M, by measuring the coil voltage and coil current of the test motor at M measurement timings over a period of N cycles of the coil voltage, respectively, a process of obtaining a voltage measurement value Es[j] and a current measurement value Is[j] at the j-th measurement timing; When a current index value that increases or decreases according to the current measurement value Is[j] is equal to or greater than a preset determination value, a process of determining that an effective voltage value Er[j] at the j-th measurement timing is equal to the voltage measurement value Es[j]; When the current index value is less than the determination value, a process of determining that the effective voltage value Er[j] is equal to zero; A process of calculating the apparent power and power factor of the test motor from the effective voltage value Er[j], the voltage measurement value Es[j], and the current measurement value Is[j] obtained at the M measurement timings; A computer program for causing a computer to execute the above.

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