JP2658067B2 - Vector control magnetic flux controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic flux control apparatus for vector control in an inverter drive of an induction motor requiring constant output control, such as a spindle drive of a machine tool.

[Conventional technology]

When the induction motor is driven by an inverter, as shown by the characteristic a in FIG. 4, when the magnetic flux is controlled to be constant, when the magnetic flux is φ and the secondary current is I ₂ , the generated torque T becomes T = kφI ₂ (1) Therefore, a constant torque characteristic, that is, a characteristic in which the output is proportional to the rotation speed is obtained. If the magnetic flux φ is inversely proportional to the rotational speed, a constant output characteristic can be obtained between the lower limit of the operating frequency determined by the allowable magnetic flux density of the motor and the upper limit of the operating frequency determined by the maximum torque of the motor.

In FIG. 4, assuming that the minimum rotation speed in the constant output control is N _B2 and the maximum rotation speed is N _M , the ratio N _M / N _B2
Is about 2 to 3.

Therefore, in order to expand the constant output control range, _NB2 is reduced to _NB1 as shown by a characteristic b indicated by a dashed line in FIG. As a result, the maximum rotational speed to output characteristic b is also increased to N _M1, the constant power control range of N _M1 / N _B1 is obtained.

[Problems to be solved by the invention]

As described above, conventionally, in order to secure constant output controllability at the time of constant speed operation with an inverter drive of an induction motor having a wide constant output control range, the output that the inverter drive can output in a speed range of _NB1 or more. Is restricted. Therefore, even during acceleration / deceleration, there is a problem that the inverter capacity must be increased in order to shorten the acceleration / deceleration time in order to operate with the output characteristics.

The present invention has been made in view of such a problem, and has as its object to reduce the acceleration / deceleration time without increasing the inverter capacity.

[Means and actions for solving the problems]

Flux control device for vector control of the present invention, in order to achieve this object, is operated constant torque issuing the rated flux value phi ₀ as the magnetic flux command phi ^* is an induction motor below the base speed, the maximum from the base speed In the vector-controlled magnetic flux control device in which the magnetic flux command φ ^* is operated in a constant output in inverse proportion to the speed during the speed, a first base speed N _B1 and a second base speed N _B2 higher than the first base speed N _B1. Means for storing the two set values of speed command N ^* and speed detection signal N
The first base speed _NB1 is selected during constant speed operation based on a means for detecting that the induction motor is accelerating and decelerating from the _FB and a signal indicating that the induction motor is accelerating and decelerating, and the second base speed during acceleration and deceleration. N
Means for selecting _B2 and the first base speed N _B1 during constant speed operation
Control means for maintaining a constant output control characteristic of an output larger than the output based on the first base speed N _B1 based on the first base speed and performing constant output control based on the second base speed N _B2 during acceleration and deceleration. .

In the present invention, an acceleration / deceleration state and a constant speed operation state are determined from a speed command, an actual speed, a torque command, and the like. The N _B1 of FIG. 4 as the base speed for the constant-speed operation, to ensure a constant output controllability. Further, at the time of acceleration and deceleration give the magnetic flux command as to increase the output N _B2 of FIG. 4 as the base speed. Thus, the acceleration / deceleration is performed based on the increased capacity of the inverter, and the acceleration / deceleration time can be reduced.

〔Example〕

Hereinafter, the present invention will be specifically described based on embodiments shown in the drawings.

FIG. 1 is a block diagram of a control circuit of a vector control inverter to which the present invention is applied. This is a block diagram of the following equations (2) to (10), which are basic relational equations for vector control for generating torque according to equation (1).

ω _s = K ₁ × I ₂ ^* / φ ^* (3) ω _n = K ₂ × N _FB (4) ω ₁ = ω _n + ω _s (5) _Im ^* = f (φ ^* ) (6) I ₂ ^* = K ₃ × T ^* (7) θ ₁ = ∫ω ₁ dt + tan ⁻¹ (I ₂ ^* / I _m ^* ) (8) I ₁ ^* = (I _m ^{* 2} + I ₂ ^{* 2} ) ^1/2 (9) ₁ ^* = I ₁ ^* ∠θ ₁ (10) In the equation (2), the magnetic flux command φ ^* is constant at φ ₀ when the actual speed N _FB is equal to or lower than the base speed N _B , and when the actual speed N _FB exceeds the base speed N _B. , becomes _{(N B / N) × φ} 0 represents the ability to constant power control for the flux command is reduced, the flux command generator 6 of FIG. 1 corresponds to this.

(3) expression slip angular velocity omega _s is proportional to the secondary current command I ₂ ^*, and a representation that is inversely proportional to the magnetic flux command phi ^*, the conversion coefficient 8 and the divider 10 of FIG. 1 This corresponds to this.

(4), (5), (8) is a relational expression for generating the angle command theta ₁ of the primary current command in the vector control.
The primary angular velocity ω ₁ is a signal obtained by adding an angular velocity ω _{n of the} motor shaft obtained from the velocity detection signal N _FB and a slip angular velocity ω _s through an adder 13, and an angle signal obtained by integrating these with an integrator 12. Is added by the adder 14 to the phase difference angle θ between the primary current command and the exciting current command. Phase difference angle θ
Is calculated by the primary current command generator 15.

Equations (6), (7), and (9) are relational equations for generating an amplitude signal of a primary current command in vector control. The excitation current command _Im ^* is obtained by converting the magnetic flux command φ ^* to the motor magnetic circuit B
-H characteristic f (φ ^* ) 9
The secondary current command I ₂ ^* is obtained by passing a torque command T ^* output from the speed controller 1 through a conversion coefficient 7 based on a motor control constant. And the amplitude signal I ₁ ^* of the primary current command
Is calculated by the primary current command generator 15.

Equation (10) indicates that the primary current command vector can be displayed in polar coordinates using I ₁ ^* and θ, and can be converted to a three-phase current command in actual control.

FIG. 2 shows an example of an inverter drive of an induction motor using the vector control method of FIG. In the figure, reference numeral 16 denotes a speed / torque controller shown in FIG. 1, which converts a speed command N ^* and a speed detection signal N _FB of a speed detector 19 such as a tachometer or a pulse generator for detecting the speed of the induction motor 18. The primary current command ^* is output as an input signal. The current controller 17 uses a CT (instrument current transformer) 20 so that the primary current flows according to the primary current command ₁ ^*.
The secondary current is detected and controlled, and as a result, the induction motor
18 generates the torque of equation (1).

FIG. 3 shows the configuration of the acceleration / deceleration detector 2 shown in FIG. In FIG. 3, the speed command N
^* (T) and the output signal N of the sample hold circuit 27 ^*
−Δt) is input to the speed command change rate monitoring function block 21 for monitoring the change rate ΔN ₁ / Δt of the speed command, and | N
^* (T) −N ^* (t−Δt) | ≧ ΔN ₁
Is set. At this time, the state signal during acceleration / deceleration is determined by the difference between the speed command N ^* (t) and the speed detection signal N _FB (t) by the speed monitoring function block 23 and the torque command T
^* Whether or not (t) is a torque limit value is detected by the monitoring function block 24, and is output from the OR circuit 25. A condition signal output from the memory 22 and an OR circuit
The status signal, which is the output of 25, is ANDed by the AND circuit 26 and output as the acceleration / deceleration signal ADI.

When the acceleration / deceleration is completed, the state signal is turned off, so that the acceleration / deceleration signal ADI is also turned off, and the memory 22 which outputs the condition signal is reset by this signal.

As described above, in the vector control inverter drive circuit shown in FIG. 1, the detector 2 during acceleration / deceleration, the base speed signal 3 during steady operation, the base signal 4 during acceleration / deceleration, and the switch 5 for switching between them are provided. The configuration is added. Accordingly, in this circuit, the acceleration and deceleration in the signal, during steady operation in addition to being able to perform the constant output control in a base speed N _B1, during acceleration and deceleration, the base speed N as shown in FIG. 3 _The output can be increased by changing to _B2 .

〔The invention's effect〕

As described above, in the present invention, in the vector control inverter drive, the base speed which is the minimum speed of the constant output control range is changed between the constant speed operation and the acceleration / deceleration, and the constant output The control characteristics are maintained, and a magnetic flux command is generated so as to generate an output higher than that during the constant output control during acceleration / deceleration. Thereby, the required constant output controllability can be ensured, and the output can be increased during acceleration / deceleration. Therefore, according to the present invention, the acceleration / deceleration time can be reduced without increasing the inverter capacity.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control circuit of a vector control inverter including a function of switching a base speed during acceleration / deceleration of the present invention, FIG. 2 is an example of an inverter drive using the vector control of FIG. 1, and FIG. FIG. 4 is a block diagram showing a configuration of a detector during acceleration / deceleration, and FIG. 4 is a characteristic diagram when an induction motor is driven by an inverter. 1: speed controller, 2: detector during acceleration / deceleration 3: base speed signal (during steady operation) 4: base speed signal (during acceleration / deceleration) 5: switch, 6: magnetic flux command generator 7: conversion coefficient ( Secondary current) 8: Conversion coefficient (slip angular velocity) 9: BH characteristic function of motor magnetic circuit 10: Divider 11: Conversion coefficient (motor angular velocity) 12: Integrator, 13, 14: Adder 15: 1 Secondary current command generator 16: Speed torque controller 17: Current controller, 18: Induction motor 19: Speed detector, 20: CT 21: Speed command change rate monitoring function block 22: Memory 23: Speed monitoring function block 24: Torque command monitoring function block 25: OR circuit, 26: AND circuit 27: Sample hold circuit

 ──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Ikuo Nagai 12-1 Otemachi, Kokurakita-ku, Kitakyushu-shi, Fukuoka Prefecture Inside the Kokura Plant of Yaskawa Electric Manufacturing Co., Ltd. (56) References JP-A-62-272889 (JP, A )

Claims (1)

(57) [Claims] When an induction motor is driven at a speed lower than a base speed, a magnetic flux command φ
^* Is operated constant torque issuing the rated flux value phi ₀ as,
In the vector-controlled magnetic flux control device that operates the magnetic flux command φ ^* at a constant output in inverse proportion to the speed between the base speed and the maximum speed, the first base speed N _B1 and the first base speed N
Means (3) and (4) for storing two set values of the second base speed _NB2 higher than _B1 and the speed command N ^* and the speed detection signal _NFB indicate that the induction motor is accelerating / decelerating. and means for detecting (2), the constant-speed operation by a signal indicating that it is accelerating or decelerating selects the first base speed N _B1, during acceleration and deceleration means for selecting a second base speed N _B2 (5) During the constant speed operation, the constant output control characteristic based on the first base speed N _B1 is maintained, and during the acceleration and deceleration, the constant output control based on the second base speed N _B2 is larger than the output based on the first base speed N _B1. A magnetic flux control device for vector control, comprising a control means for performing the control.