JPH07118951B2 - Frequency converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a frequency conversion device including an operation control unit for controlling a variable voltage and a variable frequency of an inverter unit for driving an electric motor.

[Conventional technology]

FIG. 3 is a block connection diagram of a conventional frequency converter, in which 1 is a three-phase AC power supply, 2 is a converter unit for converting the three-phase AC power supply 1 into a DC voltage, and 3 is a DC voltage into AC. The inverter unit 4 is an electric motor connected to the output side of the inverter unit 3, and the reference numeral 5 is a control unit of the inverter unit 3. FIG. 4 is a block connection diagram of the operation control unit 6 having a microcomputer configuration showing the control unit 5 in concrete form. Reference numeral 7 is a microprocessor, and 8 is a lead in which a control procedure to be realized by the microprocessor 7 is written. Only memory (hereinafter referred to as ROM), 9 is a random access memory (hereinafter referred to as RAM) for temporarily storing information required during operation of the microprocessor 7, and 10 is analog for inputting analog information. / Digital converter (hereinafter referred to as A / D converter), 11 is an input port for inputting signals necessary for controlling the operation control unit 6, and 12 is a microprocessor 7 for controlling the operation of the inverter unit 3. Output port that outputs various calculated timing signals, 13
Is a speed setter for setting the output frequency of the inverter unit 3, 14 is a frequency selection switch for selecting the highest output frequency in frequency conversion, and 15 is a voltage pattern selection switch for selecting a voltage pattern for the output frequency of the inverter unit 3. is there.

Next, the operation will be described. The frequency set value set by the speed setter 13 is converted into a digital signal by the A / D converter 10 and read into the microprocessor 7 at appropriate time intervals according to the control procedure written in the ROM 16 in advance. Further, the operation and stop information input from the input port 11 and the input information such as the frequency selection switch 14 and the voltage pattern selection switch 15 are processed. The information processed in this way is output port
It is output as a timing signal from 12 to operate the inverter unit 3 to control the operation of the electric motor 4 at a required frequency. FIG. 5 (a) shows an example in which the maximum output frequency is switched by the frequency selection switch 14, and the opening / closing of the switch 14 responds to this opening / closing with respect to the set value of the speed setter 13. Maximum output frequency ₁ (curve A) and ₂
(Curve B) can be set respectively. FIG. 5 (b) shows an example in which the relationship between the output frequency and the voltage is switched by the voltage pattern selection switch 15, and the voltage of the curves C and D corresponding to the switching is opened and closed by opening and closing the switch 15. It is possible to select a pattern.

[Problems to be solved by the invention]

Since the conventional frequency converter is configured as described above, the switch for selecting the maximum output frequency during operation is selected.
Or, when the voltage pattern selection switch 15 is operated, the control of the frequency and voltage suddenly becomes discontinuous, which causes overvoltage and overcurrent to be supplied to each part of the circuit of the operation control unit 6, and as a result, this operation control unit 6 There was a problem that the electric motor 4 was damaged.

The present invention has been made to solve the above problems, even if there is a mistaken operation of the frequency selection switch or the voltage pattern selection switch during operation, prohibiting the change of the state of the circuit operation due to this, An object of the present invention is to obtain a frequency conversion device that can reliably prevent damage to the operation control unit and the electric motor.

[Means for solving problems]

A frequency converter according to the present invention converts an alternating current into a direct current in a converter section, converts a direct current into an alternating current in an inverter section, drives an electric motor by this conversion, and operates the electric motor by a switch operation in an operation control section. The converter unit is controlled so as to operate at the variable voltage and variable frequency set as described above, and while the electric motor is in operation, the variable voltage and variable frequency set previously are set despite the change in the switch operation. The configuration is such that an operation change prohibition circuit section for continuing the operation is provided.

[Work]

The operation change prohibition circuit section in the present invention turns on or off the gate inserted between the frequency selection switch or the voltage pattern selection switch and the input port based on the signal generated while the motor is in operation. , The input of each switch input to the input port is prohibited, and acts to prevent damage accidents due to malfunction of the operation control unit and the electric motor and excessive rotation.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, 6 is an operation control section for controlling the inverter section 3, and 16a and 16b are gates provided between the frequency selection switch 14 and the voltage pattern selection switch 15 and the input port 11, from the output port 12 to the signal line. A signal sent via 17 opens and closes the gate. That is, when this signal is a high-level signal that is output during operation stop, all the signals corresponding to the opening and closing of the switches 14 and 15 can be input to the input port 11 and If it is a low level signal that is output to, all of the signals according to the opening and closing of each switch 14,15,
Input to input port 11 is disabled.

In addition, the same blocks as those shown in FIG. 4 are denoted by the same reference numerals, and the duplicated description thereof will be omitted.

Next, the operation will be described. The frequency set value determined by the speed setter 13 is converted into a digital signal by the A / D converter 10 and read into the microprocessor 7 at appropriate time intervals according to the control procedure written in the ROM 16 in advance, In addition, the operation input from the input port 11,
It is processed together with the stop information and the input information such as the frequency selection switch 14 and the voltage pattern selection switch 15.
The information processed in this manner is output as a timing signal from the output port 12 to operate the inverter unit 3 and control the operation of the electric motor 4 at a required frequency. On the other hand, while the electric motor 4 is stopped, the output port 12 of the operation control unit 6
Since a high level signal for opening the gate is input to the gates 16a and 16b through the signal line 17, the operating states of the frequency selection switch 14 and the voltage pattern selection switch 15 are read into the microprocessor 7 through the respective input ports. Be done. As a result, the microprocessor 7 determines the states of the switches 14 and 15 and stores the selection mode of the frequency pattern and the voltage pattern in the RAM (a) as data. That is, in the case of a frequency pattern, FIG.
The curve A or the curve B is selected, and in the case of the voltage pattern, the curve C or the curve D of FIG. 5B is selected. Then, such an operation is executed at appropriate time intervals, and the data is constantly updated. Next, when the electric motor 4 is in operation, the gate 16a, the output port 12 of the operation control unit 6 through the signal line 17,
Since a low-level signal for closing the gate is input to 16b, neither of the operating states of the selection switches 14 and 15 is input to the input port 11. Therefore, the data of each selection mode stored in the RAM 9 is not updated, the frequency pattern and the voltage pattern are continuously generated according to the previous data, and the inverter unit 3 is controlled to operate the electric motor 4. Therefore, even if the selection switches 14 and 15 are operated by mistake during operation, the control data of the frequency pattern and the voltage pattern for the inverter unit 3 are not changed, and the drive control of the electric motor 4 can be stably continued.

In the above embodiment, the gate is provided between the selection switches 14 and 15 and the input port 11, but the microprocessor 7 is used as the input port for the opening / closing information of the selection switches 14 and 15 by software. You may make it implement the input control with respect to 11. This soft processing is executed like the flow chart shown in FIG. That is, the operating state of the electric motor 4 is discriminated by the microprocessor 7 (step 18), and if stopped, the state of the frequency selection switch 14 is read (step 19), and the frequency pattern is further selected (step 20). Then, the voltage pattern selection switch 15
The state of is read (step 25) and the voltage pattern is selected (step 22). On the other hand, if you are driving
Each step 19-22 skips and does not cause any change in driving behavior. That is, it does not accept any input data during operation.

〔The invention's effect〕

As described above, according to the present invention, even when the frequency selection switch or the voltage pattern selection switch is operated during the operation of the electric motor, the input of the selection signal by the selection switch is prohibited by the operation signal. Therefore, even if each of the selection switches is erroneously operated during operation, it is possible to continue the previous operating state in a stable and safe manner, and to obtain a highly reliable frequency conversion device.

[Brief description of drawings]

FIG. 1 is a block connection diagram of an operation control unit in a frequency converter according to an embodiment of the present invention, FIG. 2 is a flow chart for explaining input control to an input port of opening / closing information of a selection switch, and FIG. Block connection diagram of frequency converter, FIG. 4 is a block diagram of a conventional operation control unit, FIG.
The figure is a characteristic diagram showing a frequency pattern and a voltage pattern for controlling an inverter. 2 is a converter unit, 3 is an inverter unit, 4 is an electric motor, 5
Is a control unit, 6 is an operation control unit, 7 is a microprocessor,
14 is a frequency selection switch, 15 is a voltage pattern selection switch, 16a and 16b are gates, and 17 is a signal line. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A converter section for converting AC into DC, an inverter section for converting DC output of the converter into AC, an electric motor driven by receiving the AC output of the inverter section, and setting by operating a selection switch. The operation control section for controlling the inverter section so as to operate the electric motor at the variable voltage and variable frequency, and the operation control during operation of the gate circuit provided at the connection section between the selection switch and the operation control section. A frequency conversion device comprising: an operation change prohibition circuit section that cuts off by an operation signal from the section, prohibits input of a selection signal of the selection switch, and continues operation at a previously set variable voltage and variable frequency.