JP3849857B2 - AC motor resistance measurement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resistance measurement method for an AC motor, which is performed without burning the motor to be tuned.
[0002]
[Prior art]
Conventionally, as shown in FIG. 4, the inverter device is a DC voltage obtained by converting a three-phase AC by a given DC voltage or a power element, an operator panel 20 for monitoring the operating state, displaying or changing parameters of the inverter device, and the like. Is converted again to an alternating current of arbitrary frequency and voltage by the PWM control method, and each of the power converters 1, U, V, and W phases including a voltage-type PWM inverter that supplies the primary frequency and the primary voltage to the AC motor 2 It comprises current detectors 3A, 3B, 3C for detecting the current flowing in the phase, and a control device 4 for performing vector control or V / f control. The power converter 1 is composed of a power semiconductor element, and the speed detector 5 is connected to the AC motor 2.
[0003]
FIG. 5 is a block diagram of a control device 4 that performs conventional vector control. The control device 4 receives the speed command value ωrref from the outside, detects the primary current (U-phase current Iu, V-phase current Iv, W-phase current Iw) to the AC motor 2 and performs the excitation current feedback by performing coordinate conversion. A three-phase / two-phase converter 6 is provided for sending the value Idfb and the torque current feedback value Iqfb.
Further, the control device 4 obtains a slip frequency command value ωs from Idref and Iqref, which will be described later, and a set secondary resistance r2, and calculates and outputs the primary angular frequency ω1 from the speed detection value ωr from the speed detector 6. Primary angular frequency calculation circuit 7 and speed detection value ωr as inputs, magnetic flux command calculator 14 for calculating a magnetic flux command, and coefficient unit 15 (coefficient value: 1 / M) for calculating an excitation current command Idref using the magnetic flux command as an input. * And M * are exciting inductances), and an exciting current control circuit that controls the exciting current direction voltage so that the exciting current command value Idref and the exciting current feedback value Idfb from the 3-phase / 2-phase converter 6 coincide with each other. (ACR d) 8 is provided.
[0004]
Further, the output value of the speed control circuit (ASR) 9 provided so that the speed command value ωrref and the speed detection value ωr from the speed detector 6 coincide with each other is set as the torque current command value Iqref, and the torque current command value Iqref and 3 A torque current control circuit (ACR q) 10 is provided for controlling the torque current feedback value Iqfb output from the phase / 2-phase converter 6 to coincide with the reverse due to the leakage inductance of the AC motor 2 and the primary resistance r1. There is a voltage command compensation circuit 11 that outputs the voltage of the exciting current direction component of the electromotive force, the induced voltage caused by the induced electromotive force coefficient generated by the magnetic flux of the AC motor 2, and the torque current direction component voltage of the counter electromotive force caused by the primary resistance. is doing. Among the outputs of the voltage command compensation circuit 11, the excitation current direction component voltage is added to the excitation current control circuit 8 output to generate an excitation current direction voltage command value Vdref, and the torque current direction component voltage is the torque current control circuit. The torque output direction voltage command value Vqref is generated by adding 10 outputs. Further, a two-phase / 3 for generating and outputting PWM signals of voltage commands (Vu, Vv, Vw) of U, V, W phases from the excitation current direction voltage command value Vdref and the torque current direction voltage command value Vqref. A phase converter 12 is provided.
The primary angular frequency ω1 from the primary angular frequency command calculation circuit 7 is integrated by the integrator 13 and input to the three-phase / two-phase converter 6 and the two-phase / 3-phase converter 12 as the phase θ.
Further, the control device 4 controls the excitation current command value Idref, the torque current command value Iqref, and the phase θ signal according to the tuning processing unit 30 that controls the tuning operation of the primary resistance, and the switching commands 1 to 3 from the tuning processing unit 30, respectively. It incorporates signal switchers 31-33 for switching between.
[0005]
Next, with regard to the primary resistance measurement operation performed before the operation, the tuning operation will be described in detail focusing on the operation of the tuning processing unit 30.
When primary resistance tuning is instructed, the tuning processing unit 30 determines the magnitude of the direct current to flow during resistance measurement based on the rated current value of the AC motor and the inverter to be subjected to primary resistance measurement, and switches the signal. The operation is started by switching the signal from a to b by the outputs of the devices 31 to 33. By switching the signals, the excitation current command value Idref, torque current command value Iqref, and phase θ signal are set to output values 0 and 0 from the tuning processing unit 30, respectively, and Iw = Idref, Iu = Iv = −Idref / To be 2. The control device 4 controls the voltage command so that the current detection values from the current detectors 3A, 3B, and 3C coincide with the current command value. Next, the tuning processing unit 30 takes in the voltage command values Vdref and Vqref, takes in Vref by √ (Vdref ² + Vqref ² ), takes in the current detection value Iw of the W phase, and calculates the resistance value by the ratio of Vref and Iw. .
[0006]
Next, a conventional resistance tuning operation will be described using the resistance tuning flowchart of FIG.
First, the rated current value Im100 of the electric motor is inputted through the operator panel 20 (step 10).
Next, a value obtained by multiplying the smaller one of the input rated current value Im100 of the motor and the rated current value Iinv of the inverter device (predetermined value 4) is determined as a current value to be passed during resistance tuning, and is set as Idref (step 20). . At this time, the predetermined value 4 is determined in order to achieve both accurate measurement and preventing the motor from burning out by improving the SN ratio.
Next, resistance tuning is started at Iqref = 0 and phase θ = 0 so that Idref flows in the W phase. At this time, a current of -Idref / 2 flows in each of the U and V phases (step 30). Then, the voltage command is controlled so that the current command value matches the current detection value (step 40), the voltage command value Vref at this time is calculated by √ (Vdref ² + Vqref ² ) (step 50), and Vref is measured. The resistance value is calculated by the amplitude ratio of the W-phase current value Iw (step 60).
The primary resistance tuning is performed as described above.
[0007]
[Problems to be solved by the invention]
However, in the prior art, if the rated current value of the motor that is input during tuning is set to a current value that is one digit larger due to an input error or the like, if the capacity of the power converter has a margin, the motor is excessive. An electric current would flow, and the motor could be burned out.
Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to set the resistance value of the motor without burning even if there is a setting error in the rated current value of the motor set during tuning. It is to measure safely.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides an output current flowing in each phase of an AC motor supplied via a power converter composed of a power semiconductor element capable of controlling the magnitude, frequency and phase of the output voltage. In the inverter device of an AC motor having a current detector to detect, the inverter device incorporates electrical constants of typical motors that can be applied in advance, and when performing resistance tuning, the rated current value and rating of the motor to be tuned The output power value is input, and the difference between the input rated current value and the rated output power value calculated from the electrical constant of the motor stored in advance and the input rated output power value is within a predetermined range. If it is outside, the data abnormality check function that does not perform resistance tuning is also prevented by not accepting input data. Or the rated current value of the motor to be tuned is input, and the output voltage command is limited by a value calculated based on the input rated current value and the electric constant of the motor stored in advance. It measures resistance.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 which is a flowchart of the present invention differs from FIG. 3 of the conventional example in that steps 11 and 12 are added between steps 10 and 20, and in addition to the rated current value Im100 of the motor in step 10 ′, the motor The rated output power value P is input. Since other operations with the same step name are the same, duplicate description is omitted here. The operation of the tuning processing unit 30 is exactly the same except for the operation flow described here.
[0010]
In step 11, the rated output power value of the motor to be tuned is calculated using the input rated current value Im100 of the motor and the electrical constant value of the built-in motor that has the closest rated current ( 1) Calculate with the formula and let P ′ be the calculation result.
[0011]
Im0 = Im100 × Im0_M / Im100_M
(Im100_M is the rated current value of the built-in motor, Im0_M is the excitation current value)
P '= √3 × √ (Im100 ² − Im0 ² ) × (Voltage class of inverter control device) (1) Equation Here, the ratio of excitation current Im0 and rated current of the motor to be tuned is the same as the reference motor Approximate calculation as a ratio.
[0012]
In step 12, it is checked whether the ratio between the rated output power value P ′ obtained in step 11 and the input rated output power value P is within a predetermined value 1. If it is out of the range, an input error is detected in step 10. Return to and start again from the input of the motor data. If it is within the range, start tuning.
Needless to say, when the rated output power value of the motor is calculated by the equation (1), instead of using the voltage class of the inverter control device, the base voltage of the motor can be input and the value can be used. .
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 differs from FIG. 3 in that steps 13, 20 ′, 30 ′, 40 ′, 50 ′, 60 ′, 14, and 15 are added between steps 10 and 20. Since other operations with the same step name are the same, duplicate description is omitted here.
In step 13, the limit value of the voltage command at the time of tuning is calculated by equation (2), and the value of the torque current control circuit (ACRq) 10 output is limited by this value.
Vlim = √3 × r1_M × 2 × Im100 × (predetermined value 2) (2) Formula (r1_M is the resistance value of the built-in motor)
[00013]
This step is a step of checking whether the input rated current value of the electric motor is correct before performing formal tuning. The smaller the rated current value of the motor, that is, the smaller the motor capacity, the greater the resistance value.If a large rated current value is input due to a mistake, the voltage limit will be applied during tuning. It can be prevented from flowing.
The voltage command limit in step 13 may be limited to the voltage command value itself instead of being limited by the torque current control circuit (ACRq) 10 output.
In steps 20 ′ to 50 ′, resistance tuning is performed once with a current value of Im100 * (predetermined value 2) / 100.
[0014]
In step 60 ', the resistance value at this time is calculated from the amplitude ratio of Vref and Iw, and this result is set as R10.
In step 14, if R10> = (predetermined value 3) × R1_M, it is determined that there is an input error in the rated current of the motor and the actual rated current of the tuned motor is small. Tuning is completed using the resistance value R10 obtained in step 1 as a tuning value.
If R10 <(predetermined value 2) × R1_M, the process proceeds to step 20, and tuning is performed again with the official current value (the smaller of Im100 and Iinv) multiplied by (predetermined value 4). .
The predetermined values 2 and 3 are determined in consideration of the resistance value of the cable between the motor and the inverter device, the change due to temperature, the variation of the motor (difference between the motors of the same capacity), the detection accuracy of the current detector, and the like.
If R10> = (predetermined value 3) × R1_M in step 14, instead of ending with the resistance value R10 obtained in step 60 ′ as a tuning value, the display unit displays the input / output and output state of the inverter. A warning display may be displayed on a certain operator panel.
So far, in the description of the embodiment, the description has been given of the case where the resistance value is calculated by the amplitude ratio of the voltage command value and the current detection value. The same applies when measuring the detection value and calculating the resistance value from the ratio of the difference values of the measured points.
[0015]
As described above, the rated current value and the rated output power value of the motor are set, and if there is an input setting error on one side, an abnormality check is performed according to the first embodiment, and if both have an input setting error, or the motor Even when the rated output power value is not inputted, resistance tuning can be performed or abnormal display can be performed by the second and third embodiments.
Although an example of an induction motor using an inverter device that performs vector control by feeding back a speed detector has been described, the present invention can be similarly applied to an inverter device that performs V / f control without a speed detector. The same applies to AC motors other than motors.
[0016]
【The invention's effect】
As described above, according to the present invention, there is a data abnormality check function of input data when performing resistance tuning, and a value calculated from the input rated current value and the electric constant of the motor stored in advance. Since the output voltage command is limited and the resistance is measured, there is an effect that the resistance value of the motor can be measured safely without burning even if there is a setting error in the rated current value of the motor.
[Brief description of the drawings]
1 is a flow chart of resistance tuning according to a first embodiment of the present invention. FIG. 2 is a flow chart of resistance tuning according to a second embodiment of the present invention. FIG. 3 is a flow chart of conventional resistance tuning. FIG. 5 is a block diagram showing the configuration of an inverter device. FIG. 5 is a block diagram showing the configuration of a conventional control device.
DESCRIPTION OF SYMBOLS 1 Power converter 2 AC motor 3A, 3B, 3C Current detector 4 Control apparatus 5 Speed detector 6 3 phase / 2 phase converter 7 Primary angular frequency arithmetic circuit 8 Excitation current control circuit,
DESCRIPTION OF SYMBOLS 9 Speed control circuit 10 Torque current control circuit 11 Voltage command compensation circuit 12 2-phase / 3-phase converter 13 Accumulator 14 Magnetic flux command calculator 15 Coefficient unit 20 Operator panel 30 Tuning processing parts 31-33 Signal switcher

Claims (2)

An AC motor having a current detector for detecting an output current flowing in each phase of an AC motor supplied via a power converter composed of a power semiconductor element capable of controlling the magnitude, frequency and phase of the output voltage In the inverter device,
The inverter device incorporates electrical constants of typical motors that can be applied in advance, and when performing resistance tuning, the rated current value and rated output power value of the motor to be tuned are input, and the input rated current If the difference between the rated output power value calculated from the value and the electrical constant of the motor stored in advance and the input rated output power value is outside the predetermined range, the input data is not accepted. Thus, resistance tuning is not performed, and only when the difference is within a predetermined range, input data is received and resistance tuning is performed. An AC motor having a current detector for detecting an output current flowing in each phase of an AC motor supplied via a power converter composed of a power semiconductor element capable of controlling the magnitude, frequency and phase of the output voltage In the inverter device,
The inverter device incorporates electrical constants of typical motors that can be applied in advance, and when performing resistance tuning, the rated current value of the motor to be tuned is input, and the input rated current value is stored in advance. A resistance measuring method for an AC motor, wherein the resistance is measured by limiting an output voltage command with a value calculated based on an electrical constant of the motor.

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