JPH08116676A - Variable frequency power supply - Google Patents

Abstract

PURPOSE: To obtain a variable frequency power supply for driving a pump or the like in which a motor is soft started upon turn ON power and then the motor is operated at a constant speed. CONSTITUTION: The variable frequency power supply comprises a CPU element 7 having a function for generating such waveform as the voltage and frequency increase gradually according to a voltage/frequency pattern upon interruption of a reset signal and then the voltage and frequency are settled at steady values, and a monitor element 6 for detecting turn ON power. The monitor element has an output connected with the reset terminal of the CPU element and a signal is delivered to the reset terminal of the CPU element when the monitor element detects turn ON power thus starting the waveform generating function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable frequency power supply device, and more particularly to a variable frequency power supply device (inverter device) suitable for driving a pump or the like and converting a three-phase commercial power supply into an arbitrary voltage / frequency.

[0002]

2. Description of the Prior Art FIG. 4 shows a three-phase induction motor for driving a pump, etc.
It is a block diagram of the general-purpose inverter device which converts into a frequency and supplies. In FIG. 4, reference numeral 1 is a three-phase commercial power supply terminal which is a main power supply source, reference numeral 2 is a control input terminal provided with controls such as start or stop, and reference numeral 3 is a signal from the inverter device to the electric motor. It is an output terminal.

Next, the operation of this inverter device will be described. After closing the switch (not shown) for turning on the main power source and connecting the power source, the output voltage and the output frequency are set by the key switch 4. Then, if a start signal is input to the control input terminal 2 from an externally provided additional circuit, it is soft-started as shown in FIG.
The frequency and the voltage set to are reached, the subsequent cycle is repeated, and the output terminal 3 outputs to the electric motor so as to perform constant speed operation at a predetermined voltage / frequency. The start can also be performed from the key switch 4 attached to the inverter device.

Here, the program of the CPU element 5 is constructed as shown in the flow chart of FIG. That is, when the CPU element 5 is reset by turning on the power,
A reset interrupt is generated and the CPU element 5 becomes operable. And by default, voltage / frequency (V / F)
Set the characteristics, frequency at constant speed operation, starting frequency, etc.

Next, waiting for the input of the start signal by the panel or the external addition circuit, when the start signal is input,
According to the waveform generation function program of FIG.
Transition to motor start, acceleration, and steady operation. As a result, the voltage / frequency (V / F) as shown in FIG. 5 is output to the output terminal 3 of the inverter device, and the voltage and frequency gradually increase according to a predetermined voltage / frequency pattern, After that, a certain predetermined voltage / frequency is constantly output. According to this output, the electric motor soft-starts, and then operates at a constant rotation speed.

Since the conventional inverter device is constructed as described above, after the main power is turned on for starting, a start signal is inputted from the external additional circuit through the terminal 2 or the key switch shown in FIG. You have to press the start button by 4. Also, when a power failure occurs for a certain period of time, it is necessary to input a start signal from an external additional circuit or press a start button with a key switch.

[0007]

As described above, in the conventional inverter device, unless the key switch on the operation panel or the functional device for start command is added to the outside, the inverter device does not start the operation and the power failure occurs. After that, in order to start automatically when the power is restored, it is necessary to first install an external function to detect a power failure and then to issue a start command by restoring power, which complicates the power supply. There were problems such as becoming expensive and expensive.

The present invention has been made in view of the above circumstances, and does not require the above-mentioned functional device or key switch to soft start the electric motor when the power is turned on,
It is an object of the present invention to provide a variable frequency power supply device for driving a pump or the like which can be operated at a constant speed thereafter.

[0009]

According to the variable frequency power supply device of the present invention, the voltage and frequency are gradually increased according to a certain voltage / frequency pattern by a reset signal interrupt, and then a certain voltage / frequency is applied. A CPU element having a waveform generating function for steadily outputting and a monitor element for detecting an input of a power supply voltage are provided, and the output of the monitor element is connected to a reset terminal of the CPU element, and the monitor element has a power supply voltage. CPU by detecting the input of
A signal is sent to the reset terminal of the element to start the waveform generating function.

[0010]

A CPU element is reset by a signal from a monitor element for monitoring a power supply voltage, and a reset interrupt starts a program for performing a soft start of the CPU element and a subsequent pump operation at a constant speed, and automatically starts the program. To do. Therefore, at the start of the operation of the pump, the pump can be soft-started when the power is turned on, and thereafter the pump can be operated at a predetermined constant speed. In addition, even when a power failure occurs, the pump automatically soft-starts at the same time as the power recovery, and can return to the operation at the constant speed before the power failure. Therefore, an external additional circuit for start or a key switch, which has been conventionally required, is not required, the variable frequency power supply device can have a simple structure, and the size and cost can be reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

FIG. 1 shows a circuit configuration of a main part of a variable frequency power supply device according to an embodiment of the present invention. The monitor element 6 monitors the power supply voltage in the inverter device. This output side is connected to the reset terminal of the CPU element 7. Therefore, when the main power source is turned on (ON), the output of the monitor element 6 becomes an active level, and this signal is transmitted to the CPU element 7.
Since it is input to the reset terminal of
U is reset and a reset interrupt occurs.

When a reset interrupt occurs, the program shown in FIG. 2 is started. The program of FIG. 2 is started when a reset interrupt occurs, and automatically starts based on a voltage / frequency (V / F) characteristic, a starting frequency, and a constant speed rotation frequency which are predetermined in the initial setting stage. Therefore, when the main power supply is turned on, a waveform generation program in which the voltage and frequency gradually increase in accordance with a predetermined voltage / frequency pattern is executed, and then a predetermined voltage / frequency is steadily maintained. The waveform generation program output to is executed. The induction motor of the inverter device is soft-started as shown in the graph of FIG. 5, and then shifts to a constant speed operation at a predetermined rotation speed.

By connecting the output side of the monitor element 6 to the reset terminal of the CPU element 7 having the waveform generating function, the waveform generating function can be started when the main power source is turned on. Further, the monitor element 6 may monitor the voltage, detect a change from no voltage to a predetermined power supply voltage, and activate its output.

The variable frequency power supply device of the present invention configured as described above does not require an external additional circuit for starting or a key switch, which has been conventionally required. Therefore, the structure of the power supply device is simplified, the externally added circuit or the key switch parts, which are conventionally required, are not required, and the number of assembling steps is also unnecessary. Therefore, the device can be reduced in size and cost. In addition, since the external additional circuit or the wiring of the key switch, which was required in the past, is not required, the problem of miswiring or connection failure at the installation site of the pump is eliminated, and the power supply device becomes easy to use, and reliability is improved. Is improved.

In the above embodiment, an example in which the pump is driven by a three-phase induction motor has been described, but as the load of the variable frequency power supply device of the present invention, a fan, a compressor,
Of course, other rotary machines may be used. or,
Of course, the electric motor is not limited to the three-phase induction motor, but can be applied to a synchronous electric motor or the like.

[0017]

According to the present invention as described above,
It is possible to provide a variable frequency power supply device that automatically starts the operation of a pump or the like when the power is turned on. As a result, when the pump etc. is started,
A pump or the like can be soft-started in accordance with a predetermined V / F pattern, and then can be normally operated at a constant rotation speed. In addition, at the time of power failure, the power can be restored and the pump or the like can be soft-started in the same manner to restore the state before the power failure.

Since this variable frequency power supply device does not require the input of a start signal by an external additional circuit or a key switch, which has been conventionally required, the variable frequency power supply device can be downsized and reduced in cost. . Further, the usability when used in combination with a pump or the like can be improved and reliability can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a main part of a variable frequency power supply device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a reset program according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a conventional reset program.

FIG. 4 is a block diagram of a conventional inverter device.

FIG. 5 is an explanatory diagram showing a change in voltage / frequency output with the passage of time.

[Explanation of symbols]

 1 Power supply terminal 2 Control input terminal 3 Output terminal 4 Key switch 5,7 CPU element 6 Monitor element

Claims (1)

[Claims] 1. A CPU element having a waveform generating function for gradually increasing a voltage and a frequency according to a predetermined voltage / frequency pattern by a reset signal interrupt, and then constantly outputting the predetermined voltage / frequency. And a monitor element for detecting the supply of power supply voltage, the output of the monitor element is connected to the reset terminal of the CPU element, and the reset terminal of the CPU element is detected by the monitor element detecting the supply of power supply voltage. A variable frequency power supply device, characterized in that a signal is sent to the device to start the waveform generating function.