JPS58172989A - Torque controller for induction motor - Google Patents

Abstract

PURPOSE:To enhance the controlling accuracy of a torque by dividing the secondary input by the magnitude of a frequency command to obtain the torque generated from an induction motor and feeding back and collating the generated torque with the torque command. CONSTITUTION:A primary input calculator 22 calculates the primary input of a motor 5 from the outputs of a voltage detector 20 and a current detector 21. A primary copper loss calculator 23 calculates the primary copper loss of the motor 5 from the output of the detector 21 and the preset resistance of the primary coil of the motor 5. The outputs of the primary input calculator 22 and the primary copper loss calculator 23 are added by an adder 24. The output of the adder 24 is supplied through a filter 25 to a divider 26. The divider 26 divides the output of the filter 26 by the frequency command. This output and the torque command are collated with each other and the deviation between both is applied to a slip frequency controller 27. The controller 27 outputs a slip frequency command corresponding to the polarity and magnitude of the input.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a torque control device for an induction electric machine that controls both a primary voltage and a zero frequency according to a torque command.

FIG. 1 shows a conventional example of this torque control device. In the figure, 1 is a 3-phase AC power supply, 2 is a forward converter, 3 is a DC filter, 4 is an inverse converter, and 5 is a 3-phase (U, V, W phase)
This is an induction motor (hereinafter referred to as a motor). 6 is a slip frequency calculator that multiplies the torque command (signal) τS by a constant, and the slip frequency command f8 outputted by this calculator is equal to the rotation frequency fm of the motor 5 detected by the rotation frequency detector 7.
and becomes the frequency command (signal) f+. The frequency command f is converted into a pulse signal by an oscillator 8, and then given to the inverter 4 as a frequency control signal via a divider 9 and a pulse amplifier 10, thus changing the output frequency of the inverter 4. is controlled. The frequency command f is also multiplied by a constant in the proportional amplifier 11, and then the voltage correction value (signal) △Vs
is added to the voltage command (signal) Vs. The voltage command Vs is added to the DC voltage Vd from the DC voltage detector 12 and the illustrated polarity, and the deviation (Vs-Vd) between the two is given to the voltage controller 13. The output of the voltage controller 13 becomes a current command (signal) Is, which is matched with the input current IA of the forward converter 2 taken out via the current transformer 14 and rectifier 15 and input to the current controller 16. The gate pulse phase of the phase controller 17 is controlled by the current control signal id output by the current controller 16, and the output of the forward converter 2 is controlled. Note that the voltage correction value ΔvII is to compensate for the voltage drop due to the primary resistance (resistance of the negative winding) R8 of the motor 5.
It is determined as a function of the frequency f.

In this way, in the conventional device, in order to prevent the influence of the primary resistance voltage drop of the motor 5 in the low frequency region, a voltage correction value Δv8 of a size commensurate with this voltage drop is introduced. However, since this correction value Δv1 was introduced, 1. The relationship between the primary voltage 11 (terminal voltage) vI of the motor 5 and the frequency f1 is as shown by the solid line in FIG. There was a drawback that the generated torque could not be maintained at the value of the torque command τS.

This invention was made to eliminate the drawbacks of the conventional devices described above, and it detects the primary voltage and primary current of an induction motor, calculates the torque generated by the induction motor from these detected values, and calculates the torque generated by the induction motor. It is an object of the present invention to provide a torque control device for an induction motor that can improve control accuracy compared to conventional methods by controlling the slip frequency so that there is no difference between torque and torque command.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, the same components as those in FIG. 1 are given the same reference numerals. In the figure, 20 and 21 are voltage detectors and current detectors for detecting the primary voltage (line voltage) Vt and negative current (phase current) I+ of the motor 5, respectively;
A Fi-order input computing unit, the detected primary voltage V,
and primary current I.

The primary human power P of the motor 5 is calculated from . 23 is a primary steel loss calculation unit, and the detected primary current I.

The primary copper loss Plc of the motor 5 is calculated from - The outputs of the next input calculator 22 and the primary steel loss calculator 23 are added to the illustrated polarity by an adder 24. The output of the adder 24 is supplied to a divider 26 via a filter 25 that removes high frequency components. The divider 26 receives the frequency command f as a divisor, calculates (P, -P, c)/11, and outputs the result. This output and the torque command τ3 are combined and the deviation between them τ is given to the slip frequency controller 27. The slip frequency controller 27 outputs a slip frequency command f's corresponding to the polarity and magnitude of the human input, and this slip frequency command f's and the rotational frequency fm are added to form a frequency command f.

FIGS. 4 and 5 show examples of the -order input calculator 22, the -order input calculator 23, and the vector frequency controller 27, respectively.

In FIG. 4, Vuv, Vvv and Vwu are the primary voltages between each phase detected by the voltage detector 20, and Iu
.

IW and Iw indicate phase currents detected by the current detector 21. 201, 202, and 203 are the phase voltages Vu (=Vuv−Vvu) of the U phase, ■phase, and W phase, Vv=(Vvw−
Vvv) and Vv (=Vwu-'Vvv), where the phase voltages Vu, 'Vv and Vw are multipliers 204, 205 and 206, respectively, to obtain the phase current Iu.

■Ma, iv and kake are combined. Multiplier 204゜205
and 206's respective outputs Vu I u, Vv I v
and 7w Iw are added by the adder 207 and then multiplied by the proportional amplifier zoa to provide the primary input P of the motor 5.

becomes. 231, 232 and 234 are square multipliers,
Phase currents In, 1 and IW are input, respectively, and the outputs are added by an adder 235. The output of the adder 235 is multiplied by R1 by the proportional amplifier 236, and becomes the primary steel losses P and e of the motor 5.

In Fig. 5, (g) is an inverting amplifier, ('1) + (r
, ) is a resistor, and (C) is a capacitor, which proportionally integrates the torque deviation Cτ and outputs it as a slip frequency command f'a.

Next, the operation of this device will be explained.

Generally, the iron loss and mechanical loss of the motor 5 are negligibly small compared to the primary input, so if this is ignored, the output of the adder 24 (P+Pc) will be - the secondary human power pt of the motor 5. Equivalent to this secondary human power P.

The output of the divider 26 that divides the frequency command f by the frequency command f can be made to correspond to the generated torque τ since the following relationship holds between the generated torque τ of the motor 5 and the secondary input Pt.

P 2 = W o r ・・・・・・・・・
(1) However, Wo: Synchronous angular speed of the motor 5 Now, when the motor 5 is under-excited and the generated torque τ becomes smaller than the torque command τS, a positive deviation Cτ occurs, and the slip frequency which is the output of the slip frequency controller 27 command f
Since s increases in proportion to eτ, motor 5 automatically
The generated torque T is controlled to the torque command value T8. Conversely, when the motor 5 becomes over-excited and τ>τ8, the deviation 8τ becomes negative and the slip frequency command (fs) becomes small, so the generated torque T is controlled to the torque command value τS.

FIG. 6 shows another embodiment of the present invention.
The value obtained by adding the slip frequency △f's to the slip frequency command fs of the conventional device shown in the figure is added to the rotating cylinder wave number fm and the frequency command f1 is obtained, so the slip frequency △f corresponding to τ - τB 's only is corrected by the slip frequency controller 27.

In addition, in the said Example, the primary voltage of the motor 5 is.

Variable voltage variable frequency to control frequency! As the neck
P, AM type voltage inverter is used, but P W M
A similar effect can be obtained in the case of molds.

As described above, according to the present invention, the secondary input of the induction motor is calculated from the primary voltage and the negative current of the induction motor, and the generated torque of the induction motor is calculated by dividing the secondary input by the magnitude of the frequency command. By having a configuration in which the generated torque is fed back and compared with the torque command, the torque control accuracy can be improved compared to the conventional method.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional induction motor torque control device, Fig. 2 is a diagram showing the primary voltage-frequency relationship of the induction motor operated by the variable speed control device, and Fig. 3
The figure is a block diagram of an embodiment of a torque control device for an induction motor according to the present invention, FIGS. 4 and 5 are block diagrams and circuits of specific examples of essential parts in the above embodiment, respectively, and FIG. 6 is a block diagram of an embodiment of a torque control device for an induction motor according to the present invention. FIG. 2 is a block diagram showing a part of an embodiment of the invention. In the figure, 20...voltage detector, 21...current detector, 22...-next input arithmetic unit, 23...-next input arithmetic unit, 24...adder, 26... Divider. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Makoto Kuzuno - Figure 1 Figure 3 Figure 3 Continued from page 1 0 Inventor Hideaki Tomei Mitsubishi Electric Corporation Control Manufacturing Works, 1-1-2 Wadazaki-cho, Hyogo-ku, Kobe 0 Inventor Sadanari Yano Inside the Mitsubishi Electric Corporation Control Plant, 1-1-2 Wadazaki-cho, Hyogo-ku, Kobe City

Claims (1)

[Claims] In a torque control device that controls the primary voltage and frequency of an induction motor according to a torque command, the next input to the induction motor is determined by receiving the outputs of a voltage detector that detects the primary voltage of the induction motor and a current detector that detects the primary current. A primary input calculator that calculates the primary steel loss from the output of the current detector and the preset induction resistance of the 4m motor, a primary input calculator that calculates the primary steel loss, the -next input calculator, and the -next input calculator. a subtracter that receives the output and calculates the difference between the two river forces; a divider that divides the output of the subtracter by a frequency command that commands the frequency;
A slip frequency controller is provided which calculates a slip frequency command based on the difference between the output of the divider and the torque command, and the frequency command is given as a sum of the frequency command and the rotational frequency of the induction motor. Features: Torque control device for induction motors.