JPS61231891A - Setting method for constant inverter - Google Patents

Abstract

PURPOSE:To obtain an accurate control by simply measuring the primary resistance which varies according to a cable and a motor of various specifications, and automatically setting the control constant of an inverter. CONSTITUTION:A DC voltage is applied to an AC motor 2 by a PWM inverter prior to the operation of the motor 2. The primary resistance of the motor is obtained by a function generator 9 and a resistance calculator 10 from the output voltage command value vu and the output current iu of an inverter 1. This measured and calculated result is set to a motor driven force calculator of a block 8 to accurately compensate the voltage drop due to the primary resistance by the motor voltage. As a result, the inverter of the control type can be initialized on the basis of the induced power of the motor.

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 rotation speed detector was not necessary. However, since the system becomes complicated, a control method that does not use a rotational speed detector is required. For example, Japanese Patent Laid-Open No. 59-63998 discloses a method in which the motor terminal voltage is detected and control is performed 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 to set the core, 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 control errors. You must set that constant to .

There is a problem in that it takes a lot of time to set up and adjust the WR.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned problem, and by measuring the primary resistance of the motor constant using an inverter device and automatically setting the constant in the inverter device based on that, there is no need for adjustment and a high An object of the present invention is to provide an inverter device having accurate control performance.

[Summary of the invention]

A feature of the present invention is that, prior to operation of the motor, a DC voltage is applied to the motor using an inverter, and the primary resistance of the motor can be determined from the ratio of the inverter's output voltage command value and output current. Based on this, the constants of the inverter device are automatically set.

[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. Reference numeral 1 denotes a pulse width modulation PWM inverter that supplies variable frequency alternating current to a three-phase induction motor 2. In FIG. First, the coordinate converter 4 is sent from the control command device 3.
3-phase alternating current command 1.
m”, l v”l l *” are output.

This current command Lm'' is the output current i from the current detector 5,
The deviation is output from the AC current controller (ACR) 6 as an output voltage command V,'', and based on this, the PWM
Control the inverter. On the other hand, the voltage of each phase vm + II is detected by the voltage detector 7 provided between the inverter output terminals.
H11 is detected, and the induced electromotive force E of the motor is determined from the electromotive force calculator 8.

By returning the value to the control command unit 3, vector control is performed.Blocks 5, 6, and 7°8 are 3 in total.
Although there are two phases, illustration of two phases is omitted here. In addition, 9.10 is used for measuring the primary resistance, 9 is a function generator that outputs a signal v4° according to the magnitude of the output current i, and 10 is a function generator that outputs the signal v4° and i,,v,'' This is a resistance calculator that calculates the primary water resistance r1 of the motor, and the constant of the primary voltage drop of the electromotive force calculator 8 is set based on this calculation result.

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 current command i, 8 (=i, , , is given, and the characteristics (i, , ``-v, , '' characteristics) of the output voltage command V,'' (=V 4°'') for this ldm are stored in a memory element or the like.

Here, v,,” is expressed as the following formula: vae”=v, a (1is) + Rio...(
1) That is, 4.1 is an internal voltage drop v due to the on-delay of the inverter in addition to the voltage drop of the resistor R.

Contains. This vo is non-linear with respect to i4°, and although its magnitude varies depending on the PWM frequency and the switching elements constituting the main circuit, v remains the same for the same inverter. Next, after shipment from the factory, the electric motor is connected to an inverter and operated. Prior to operation, the single water resistance r1 of the electric motor is measured using blocks 9 and 10. The measurement calculation method will be explained. First, a direct current i, = i, is applied to the motor from the inverter. The current command 1'u'' (=l do) is set so that im flows, and the output voltage command v, 8 for im is set by the resistance calculator 1o.
i,. Enter both. On the other hand, i. is input to the function generator 9, and the output v4. obtained by equation (1) is obtained. Resistance calculator 1
By inputting 0, the motor's water resistance r1 can be obtained as follows. That is, 1de of the function generator in FIG.
-va. In the characteristic diagram, the mark X indicates direct current i to the motor.

is the output voltage command V,'' when the same value of DC 1 da is applied to the known resistance R. Here, the internal voltage drop of the inverter v0.
Since ldm is the same, van in both is the same. Therefore, both output voltage commands V, ″ and ′
Since the difference 4■ from l/4 is an increase due to the resistance stand, the primary resistance r of the motor can be calculated from the following equation, and this calculation is performed in block 1o.

Therefore, by setting this measurement calculation result to the electric power calculator in block 8, the voltage drop due to the primary resistance can be compensated for more accurately than the motor voltage. This will allow you to initialize the device.

The primary resistance measurement calculation method described here is not only applicable to the vector control inverter device shown in one embodiment, but also to various inverters such as V/F inverter devices that control the ratio of voltage and frequency at a constant value. Needless to say, it can also be applied to.

〔Effect of the invention〕

According to the present invention, the primary resistance, which varies depending on the cables and motors of various specifications, can be easily measured using an inverter device without using a special measuring device, and the control constants of the inverter can be automatically set.

This has the effect of eliminating the need for inverter adjustment and providing highly accurate control performance.

[Brief explanation of drawings]

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 present invention in detail.

Claims (1)

[Claims] 1. In a pulse width modulation inverter device that controls an AC motor, a load device whose resistance value is known in advance is connected to the inverter device, and the inverter output voltage command value when a predetermined DC current is passed through the load device is calculated in the inverter device. Next, when the AC motor is operated by an inverter device, a DC current having the same value as the current is passed through the AC motor from the inverter device prior to operation,
Measure the inverter output voltage command value at that time, measure the primary resistance of the AC motor from the ratio of the value obtained by subtracting the output voltage command value from this value and the DC current value, and control the inverter device based on this. A constant setting method for an inverter device, the method comprising setting a constant.