JPS6264287A - Slip correction control type inverter - Google Patents

Abstract

PURPOSE:To normally correct a slip near the maximum output frequency of an inverter by inserting the maximum speed clamping circuit & between a speed command and a cushion circuit. CONSTITUTION:The maximum speed clamping circuit 15 inputs a speed command 1, and is inserted to a cushion circuit 2. Since the frequency does not rise 60Hz or higher of the maximum frequency of an inverter 7 when a slip frequency is 1Hz of higher, a normal correction becomes impossible. Thus, a gain is regulated so that a speed command is input to the cushion circuit 2 only when the command falls within a voltage lower by the voltage corresponding to the maximum slip frequency to be corrected by reducing the gain of the clamping circuit 15.

Description

[Detailed Description of the Invention] [Industrial Applicability Meter] This invention detects the amount of slip of an AC induction motor, and uses the rotational speed of the AC induction motor to respond to a speed command given in advance, regardless of the amount of slip. The present invention relates to an inverter device using a slip correction control method that performs feedback control to keep the velocity within a certain range.

[Conventional technology]

FIG. 3 is a block diagram showing an inverter device using a conventional slip correction control method as shown in, for example, New Drive Electronics (authored by Naohiko Ueyama, published by Denkishoin), where %1 is a speed command input to the cushion circuit 2, and 3 is a slip amplifier circuit whose input is the difference between the cushion circuit 2 and the tacho generator 9, 4 is a slip clamp circuit, 6 is the output of the summing amplifier circuit 5, and is a frequency command that is input to the inverter T, and 8 is an AC induction motor. .

Next, the operation will be explained. To simplify the explanation, first, open loop control without slip correction control will be explained. The speed command 1 performs a cushion operation in which the speed command 1 is gradually increased or decreased over a certain period of time during acceleration or deceleration by the cushion circuit 2. Now assuming that the output of the slip clamp circuit 4 is zero, the frequency command 6 that is the output of the summing amplifier circuit 5 becomes the output of the cushion circuit 2 itself, and the inverter T is
Upon receiving the command, the AC induction motor 8 is driven. here,
Naturally, when a load is applied to the AC induction motor 8, the rotation speed changes. Next, consider the case of FIG. 3 in which slip correction control, which is feedback control, is performed. The difference between the one rotational speed detected by the tacho generator S and the output of the cushion circuit 2 is detected and amplified by the slip amplifier circuit 3, and the difference between the output of the cushion circuit and the summing amplifier is calculated as a correction amount 12 through the slip clamp circuit 4 (i- It is added and corrected in circuit 5 and sent back to the inverter's frequency command. In other words, the variation in rotational speed is detected and amplified as a vector amount, and the amount of slip is corrected based on the inverter's frequency command, thereby improving speed accuracy in an open loop. The correction characteristics are shown in Fig. 4.As shown in Fig. 4, when the load amount 13 of the AC induction motor increases, the rotational speed 11 decreases once, but the slip amplifier circuit 3 The correction amount 12 increases with a time constant determined by, etc., and the rotation speed 11
The speed fluctuation is suppressed to a value determined by the gain of the slip amplifier circuit.

[Problem that the invention seeks to solve]

Since the conventional inverter device using the slip correction control method is configured as described above, when the AC induction motor 8 is operated with the speed command 1 set near the maximum output frequency of the inverter T, the load amount 13 is applied to the power side. increases, the smooth fan circuit 3 sends out a correction amount 12 in order to correct the amount of slip, and reflects the inverter frequency command 6 rather than increasing it, but the inverter 7 outputs no more than the maximum output frequency. Unfortunately, there was a problem in that the slip correction was not performed properly. In addition, when the speed command 1 corresponds to the highest output frequency and the frequency command is 6 or higher, the slip amplifier circuit 3
is saturated, so when decelerating from the above state, at the point where the slip amplifier circuit 3 returns to normal operation from the saturated state, a step occurs in the frequency command of the inverter, and the rotational speed does not decelerate smoothly. There were also problems such as the inverter stopping due to regenerative overvoltage disconnection.

This invention was made in order to solve the above-mentioned problems, and it covers the area f where slip correction cannot be performed normally near the maximum output frequency of the inverter, and also prevents abnormalities during deceleration due to saturation of the slip amplifier circuit. The object of the present invention is to obtain an inverter device using a slip correction method that can eliminate the operation.

[Means for solving problems]

The slip correction type inverter device according to the present invention operates by inserting a maximum speed clamp circuit between the speed command and the cushion circuit.

[Effect]

The maximum speed 2271 circuit in this invention cranks with the upper limit of the speed command, and sends the frequency command to the inverter in region 2 where slip correction cannot be performed normally near the maximum output frequency of the inverter and in the region where the speed command is larger than the frequency command. to avoid being

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same parts as in FIG. 3 of the conventional example are indicated by the same reference numerals, and 15 is a speed command 1f: input.

This is the highest speed clamp circuit inserted between 27,717 times 42. FIG. 2 shows a detailed circuit diagram of one embodiment of the maximum speed clamp circuit 15. In FIG. 2, 17 is a resistor connected to the input side of the operational amplifier 16, and 18 is a variable resistor inserted between the output side and the input side of the operational amplifier 16.

Next, the operation will be explained. Now, suppose that the inverter 7 outputs a frequency of 6Of(z) when the frequency command 6 is IOV, and even if a frequency command 6 with a value higher than that is input, it will not output a frequency of 60 or more. In other words, the highest frequency is 60 out.

For comparison, consider the conventional example shown in FIG. Assuming that the inverter outputs the highest frequency of 607 when the speed command 1 is 10 V O, suppose that the AC induction motor 13 is operated at a synchronous speed with a frequency of 59 Hz, then the load is applied to the speed command AC induction motor 8. If the
The frequency command is increased by adding the correction amount 12 corresponding to the slip to the speed command 1, but if the slip is 17 or more at the slip frequency, the frequency does not rise to 607 or more, which is the highest frequency of the inverter 7, so normal correction is not possible. It becomes impossible. This is the first problem. Also, if a speed command higher than IOV is input, the corresponding output frequency will be changed to the inverter T.
Since the slip amplifier circuit 3 is not outputted, the slip amplifier circuit 3 becomes saturated, and when the slip amplifier circuit 3 returns from saturation to the normal state during deceleration, a step occurs in the speed. This is the second
This is the problem. Therefore, if the speed command is limited by the maximum speed clamp circuit 15 as in this embodiment, the problems that occur in the conventional example described above can be eliminated. In this embodiment, a circuit as shown in FIG. 1!2 is used as the maximum speed clamp circuit 15, and the gain is lowered by a variable resistor 18 to achieve this. In other words, if the gain is adjusted so that the speed command is input to the cushion circuit 2 only to a voltage lower by the voltage (Vsb) corresponding to the slip frequency of the maximum slip to be corrected, the first problem and wIJ2 problem described above can be solved. solve. Let the maximum value of the speed command applied as an intervention force be 'il OV, and let the maximum slip to be corrected be t-3Hz. Konotogi vs.
L is. Therefore, the variable resistor 18 of the maximum speed clamp circuit 15 may be set so that the gain Gt-0.95.

In the above embodiment, a variable gain amplifier was used as a circuit for clamping the upper limit of the maximum speed.

Without being limited to this, the question is whether to apply a limiter to the output of the operational amplifier or to apply a limiter to the input.

Or, by setting up a priority circuit that prioritizes small signals, etc.
As long as the upper limit of the maximum speed is limited, the same effect can be achieved no matter what kind of circuit is used.

Further, even if the maximum speed clamp circuit is inserted into the output of the cushion circuit, the same effect can be obtained.0 [Effects of the Invention] As described above, according to the present invention, the maximum speed clamp circuit is configured to clamp the upper limit of the speed command. Therefore, there is no region where slip correction cannot be performed normally near the inverter's highest frequency, and the speed command is

Since the saturation phenomenon of the slip amplifier circuit that occurs when the frequency exceeds the command frequency does not occur, control characteristics can be improved such as smooth deceleration during deceleration.

[Brief explanation of drawings]

2) is a circuit diagram of an inverter device using a slip compensation control method according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a maximum speed clamp according to an embodiment of the present invention, and FIG. FIG. 4 is a circuit configuration diagram of an inverter device using a correction control method, and is an operation diagram of correction. 1 is speed command, 2- is cushion circuit, 3 is slip amplifier circuit, 4 is slip ramp circuit%, 5 is addition amplifier,
6 is a frequency command, 7 is an inverter, 8 is an AC induction motor, and 15 is a maximum speed clamp circuit. Patent applicant Mitsubishi Electric Co., Ltd. agent Patent attorney 1) Hiroshi Sawa ゛゛ (and 2 others) -'' Fig. 1 1f6? 5 10: R'/N top times "Hr Riel 12: Amount of correction Figure 4 Procedural amendment (voluntary) 61, 7. -3 Showa year month day

Claims (2)

[Claims] (1) A cushion circuit that takes a speed command as an input and gradually increases or decreases its output at an arbitrary time limit, and a slip amplifier circuit that operationally amplifies the amount of slip that is the difference between the output of this cushion circuit and the rotational speed of an AC induction motor; A slip clamp circuit clamps the output of this slip amplifier circuit so that it is below a certain value, an addition amplifier circuit that adds the output of the slip clamp circuit to the output of the cushion circuit, and a An inverter device using a slip correction control method that takes a command input and outputs a frequency proportional to the input command to drive the AC induction motor, further comprising a clamp circuit that clamps the upper limit of the speed command. Inverter device with deflection correction control method. (2) An inverter device using a slip correction control method according to claim 1, further comprising a clamp circuit that clamps the upper limit of the cushion circuit.