JPH0568957B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an inverter device for controlling an AC motor, and in particular, the inverter device is provided with a function of measuring the primary resistance of the motor, and the control constants of the device are automatically determined. on how to set it up.

[Background of the invention]

In order to control the speed of an AC motor with high precision using an inverter device, a rotational speed detector has been indispensable. However, since the system becomes complicated, a control method that does not use a rotational speed detector is required. For example, Japanese Patent Application Laid-Open No. 59-63998 uses a method that detects the motor terminal voltage and performs control using the induced electromotive force determined from this. However, in this method, it is necessary to compensate for the first-order impedance voltage drop from the motor terminal voltage. be. Normally, the design values of the motor constants are considered to be used for setting this part, but in that case, there is a problem that the resistance of the cable between the inverter device and the motor is not included, resulting in a control error. must set that constant to
There is a problem in that it takes a lot of time to set up and adjust.

[Object of the Invention] The object of the present invention is to solve the above-mentioned problem, and by measuring the primary resistance of the motor constant with an inverter device and automatically setting the constant in the inverter device based on the measurement, An object of the present invention is to provide an inverter device that does not require adjustment and has highly accurate control performance.

[Summary of the invention]

A feature of the present invention is that, in a method for setting control constants in an inverter device that drives and controls an AC motor, a load device whose resistance value is known in advance is connected to the output end of the inverter device, and a predetermined DC current is applied to the load device. The inverter output voltage command value when the current is applied is stored in a memory element or the like in the inverter device, and then when an AC motor is connected to the output end of the inverter device and operated, the inverter output voltage command value is stored in the inverter device prior to operation. The same value as the DC current when the DC current is applied to the load device is passed through the AC motor, the inverter output voltage command value at that time is measured, and from this command value, the DC current when the DC current is applied to the load device is determined. The primary resistance of the AC motor is measured from the ratio of the inverter output voltage command value subtracted from the magnitude of the DC current and the resistance value, and the control constant of the inverter device is set based on this. .

[Embodiments of the invention]

FIG. 1 shows a circuit configuration of a pulse width modulation vector control inverter device according to an embodiment of the present invention. 1 is a pulse width modulation PWM inverter that supplies variable frequency alternating current to the three-layer induction motor 2. First, the control command device 3 sends an excitation current command i _d ^* to the coordinate converter 4,
Give torque current command i _g ^* and primary frequency command _l ^* 3
Outputs phase alternating current commands i _u ^* , i _v ^* , i _w ^* . This current command i _u ^* is compared with the output current i _u from the current detector 5, and the deviation is outputted from the alternating current controller (ACR) 6 as an output voltage command v _u ^* , and based on this,
Control PWM inverter. On the other hand, the voltage detector 7 installed between the inverter output terminals detects the voltages V _u , _v , _w of each phase, and the electromotive force calculator 8 calculates the induced electromotive forces E _u , _v , _w of the motor. Vector control is performed by feeding back the value to the control command device 3. Although the blocks 5, 6, 7, and 8 have three phases in total, illustration of two phases is omitted here. Further, 9 and 10 are used for primary resistance measurement, and 9 is a function generator that outputs a signal V _dc according to the magnitude of the output current i _u , and 10 is a function generator that outputs a signal V dc according to the magnitude of the output current i u , and 10 is a function generator that outputs a signal V _dc according to the _magnitude of the output current i _u and ¹⁰ This is a resistance calculator that calculates the primary resistance _r1 of the electric motor, and a constant for the primary voltage drop of the electromotive force calculator 8 is set based on the result of this calculation. The input/output characteristics of the function generator 9 are set in advance at the time of shipment from the factory as follows. As shown in Fig. 2, a load device 11 with a known resistance value R is connected to the output terminal of the inverter 1, and a direct current i _dc is applied to the load device 11.
A current command i _u ^* (= i _dc ) is given so that the current flows, and the characteristics (i _dc ^* − V _dc ^* characteristics) of the output voltage command V _u ^* (= V _dc ^* ) with respect to this i _dc are applied to the memory element, etc. Remember.

Here, V _dc ^* is expressed as the following formula: V _dc ^* = V _po (i _dc ) + R・i _dc ...(1) In other words, V _dc ^* is due to the on-delay of the inverter, etc. in addition to the voltage drop of the resistor R. internal voltage drop
Contains V _po . This V _po is nonlinear with respect to i _dc , and its magnitude varies depending on the PWM frequency and switching elements constituting the main circuit, but _po remains the same if the inverter is the same. Next, after shipping from the factory, the electric motor is connected to an inverter and operated, but prior to operation, blocks 9 and 10 are
Measure the resistance r ₁ of the motor by: The measurement calculation method will be explained. First, set a current command i _u ^* so that a direct current i _u = i _dc flows from the inverter to the motor.
(= i _dc ), and output voltage command V _u ^* for i _dc
Both i _{and dc} are input to the resistance calculator 10. On the other hand, i _dc
is input to the function generator 9, and the output obtained from equation (1) is
By inputting v _dc into the resistance calculator 10, the primary resistance r ₁ of the motor can be obtained as follows. That is, in the i _dc - v _dc characteristic diagram of the function generator shown in Figure 3, the x mark is the output voltage command _u ^* when direct current i _dc flows through the motor, and the ○ mark is the same value for the known resistance R. This is the output voltage command V _dc when a direct current i _{dc of} is applied. Here, since the internal voltage drop _Vpo of the inverter is the same in i _dc , the _vpo in both is the same. Therefore, since the difference Δv between the two output voltage commands v _u ^* and v _dc is an increase due to the resistance, one resistance r ₁ of the motor
can be calculated from the following equation, and this calculation is performed in block 10.

r ₁ = v _u ^* −v _dc / i _dc + R ...(2) Therefore, by setting this measurement calculation result to the electric power calculator of block 8, the voltage drop due to the primary resistance can be reduced from the motor voltage. Compensation can be performed with high precision, and as a result, initial settings of an inverter device using a control method based on the motor induced electric power can be performed.

In addition to being applied to the vector control inverter device shown in one embodiment, the one-pair resistance measurement calculation method described here can also be applied to various inverters such as V/F inverter devices that control the ratio of voltage to frequency at a constant value. Needless to say, it can also be applied to.

〔Effect of the invention〕

According to the present invention, the inverter device is used to easily measure the primary resistance that changes depending on the cables and motors of various specifications without using a special measuring device, and the inverter control constants are automatically set.
This has the effect of eliminating the need for inverter adjustment and providing highly accurate control performance.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of an inverter device showing one embodiment of the present invention, and FIGS. 2 and 3 are diagrams explaining the operation of the present invention. 1...PWM inverter, 2...AC motor,
9...Function generator, 10...Resistance calculator.

Claims (1)

[Scope of Claims] 1. In a method for setting control constants in an inverter device for driving and controlling an AC motor, a load device whose resistance value is known in advance is connected to an output end of the inverter device, and a predetermined DC current is applied to the load device. The inverter output voltage command value when the current is applied is stored in a memory element or the like in the inverter device, and when the AC motor is connected to the output end of the inverter device for operation, the inverter output voltage command value is stored in the inverter device prior to operation. When a DC current of the same value as that when flowing a DC current to the load device is applied to the AC motor, the inverter output voltage command value at that time is measured, and a DC current is applied to the load device based on this command value. measuring the primary resistance of the AC motor from the ratio of the value obtained by subtracting the inverter output voltage command value from the magnitude of the DC current and the resistance value, and setting the control constant of the inverter device based on this. Characteristic constant setting method for inverter equipment.