JP2008002380A - Additional inverter for compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an additional converter for a compressor which can be added on an existing electric motor drive air compressor and can switch over to a power source at the time of a failure of an inverter. <P>SOLUTION: This additional inverter for a compressor is equipped with a bypass circuit 11 for coupling a three-phase AC power source 9 to the electric motor drive air compressor 2 without passing through the inverter 1, and shut-off switches 12A, 12B, and 12C provided between the electric motor drive air compressor 2 and the inverter 1, between the inverter 1 and the three-phase AC power source 9, and in the bypass circuit 11, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a retrofitting inverter for a compressor. Specifically, the present invention relates to an inverter incorporating a circuit that can be easily connected to an existing air compressor.

  Conventionally, in the manufacturing industry, an electric motor-driven air compressor has been frequently used as a drive source for various machines. This electric motor-driven air compressor is designed to be able to operate with high energy efficiency at the maximum load, but the energy efficiency when the load is low is extremely poor. This is because the rotation speed of the electric motor is constant, and capacity control is performed with a suction throttle, so in the general manufacturing industry, the load factor varies greatly by 30 to 80%, which is a bottleneck for energy saving.

  Therefore, recently, an electric motor driven air compressor equipped with an inverter has been developed to promote energy saving. Since this inverter control adjusts the rotational speed of the motor according to the load and performs capacity control, efficient energy-saving operation is possible.

  Normally, inverter control is designed to detect discharge pressure and current consumption, and to control energy consumption in a detailed manner with a complicated arithmetic circuit, so it is damaged by lightning strikes, abnormal voltage, etc., or is inferior due to dust, dust, etc. If there is an abnormality in the inverter due to external factors and it becomes difficult to continue operation by the inverter, for example, there is a circuit equipped with a circuit that avoids the inverter and switches to commercial power (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 7-208371

  However, electric motor-driven air compressors equipped with inverters are expensive, and it is expensive to replace existing electric motor-driven air compressors that are in operation, and the invested capital can be fully recovered by reducing power costs. There is no problem.

  By the way, when the inverter breaks down, the compressor cannot be operated until the inverter is restored, which may hinder production. Even if a circuit that switches to commercial power by avoiding the inverter is used, the compressor must be stopped while the inverter is being repaired, or the compressor can be operated directly from the main power source, so the large capacity In the case of an electric motor, it may become impossible to start due to an excessive inrush current at the time of starting.

  The present invention was devised in view of the above points, and provides a retrofitting inverter for a compressor that can be retrofitted to an existing electric motor-driven air compressor and can be switched to a power source when the inverter fails. is there.

  In order to achieve the above object, a compressor retrofit inverter according to the present invention is an inverter in which an electric motor drive air compressor and a three-phase power source are connected by a power cable, and the three-phase without passing through the inverter. A bypass circuit for connecting a power source and the electric motor-driven air compressor, the electric motor-driven air compressor and an inverter, a cutoff switch provided between the inverter and the three-phase power source and the bypass circuit, and when the inverter is operated, The shutoff switch between the bypass circuits is turned off, and when the inverter fails, the shutoff switch between the bypass circuits is turned on, the electric motor drive air compressor and inverter, and the inverter and the three-phase The cut-off switch Minamotoma provided with a power circuit switching switch turned OFF.

  Here, when an inverter is connected to an operating electric motor drive air compressor, the number of revolutions of the electric motor is controlled, so that efficient operation is possible and energy saving is achieved, and the inverter fails for some reason However, it is a retrofitting inverter for a compressor that can immediately restart the electric motor drive air compressor with a power circuit changeover switch and minimize the damage caused by production stoppage.

  In the compressor retrofit inverter of the present invention, by connecting the inverter to an existing air compressor in operation, the discharge pressure load status is judged, and the number of revolutions of the electric motor of the air compressor is determined by the compressor retrofit inverter according to the load. The power consumption can be greatly reduced.

  In addition, if the inverter is damaged due to lightning strikes, etc., the power circuit selector switch can be used to connect the power supply directly to the air compressor without going through the inverter, resulting in production stoppage without stopping the operating air compressor. Damage can be minimized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings to provide an understanding of the present invention.
FIG. 1 is a block circuit diagram showing an example of a compressor retrofit inverter to which the present invention is applied, and FIG. 2 is an operation switching circuit diagram of a compressor retrofit inverter to which the present invention is applied.

  In the compressor retrofit inverter 1 shown here, the power cable 5A connected to the output terminal 10A of the compressor retrofit inverter 1 is connected to the delta magnet switch 4 of the star delta starter panel 3 of the existing air compressor 2. The air compressor 2 is connected to the air tank 6 by a discharge air pipe 16 so that compressed air is supplied from the air tank 6 to a machine tool or the like.

  The air pressure in the air tank 6 is measured by a pressure sensor 7, and the pressure detection signal is transmitted to a capacity control load signal circuit (not shown) provided in the inverter panel 8 of the compressor retrofit inverter 1. .

  The input terminal 10B of the compressor inverter 1 is connected to a three-phase AC power source 9 by a power cable 5B.

  Here, a bypass circuit 11 for connecting the air compressor 2 and the three-phase AC power source 9 without using the compressor retrofit inverter 1 is provided. The bypass circuit 11 includes a power cable 5B connected between the three-phase AC power source 9 and the input terminal 10B of the compressor inverter 1, an output terminal 10A of the compressor inverter 1, and a star delta of the air compressor 2. A power cable 5 </ b> C is connected between the power cable 5 </ b> A connected between the delta magnet switches 4 of the start panel 3.

  The power cable 5A includes a cutoff switch 12A, the power cable 5B includes a cutoff switch 12B, and the power cable 5C includes a cutoff switch 12C.

  In addition, each of the cutoff switches 12A, 12B, and 12C can freely switch the cutoff switches 12A, 12B, and 12C on and off by a one-touch operation of a power circuit switch 13 that is attached to the compressor retrofit inverter 1. It is to be configured.

  In the compressor retrofit inverter of the present invention having such a configuration, the power cable connected to the output terminal 10A of the compressor retrofit inverter 1 to the delta magnet switch 4 of the star delta starter panel 3 installed in the existing air compressor 2 The inverter can be retrofitted easily by connecting 5A.

  Therefore, the compressor operation switch 14 provided in the compressor retrofit inverter 1 is turned on to drive and rotate the electric motor 15 of the air compressor 2. By driving the electric motor 15, compressed air is sent to the air tank 6 through the discharge air pipe 7.

  In this case, the power circuit changeover switch 13 connects the cutoff switch 12A of the power cable 5A and the cutoff switch 12B of the power cable 5B, and the cutoff switch 12C of the power cable 5C is cut off.

  Here, the compressed air that is press-fitted into the air tank 6 is discharged according to the load of the machine tool or the like, and the discharge pressure at this time is provided in the inverter panel 8 of the compressor inverter 1 by the pressure sensor 7. Is transmitted to a capacity control load signal circuit (not shown), the load condition is judged, and the number of revolutions of the electric motor 15 of the air compressor 2 is controlled by the compressor retrofitting inverter 1 according to the load.

  In this way, the capacity control by the compressor retrofit inverter 1 can obtain a further energy saving effect by setting the discharge pressure to an arbitrary pressure.

  The capacity control is performed by controlling the number of revolutions of the electric motor up to the minimum capacity control range of the air compressor, and the operation is switched to the capacity control (normal intake air amount adjusting valve) unique to the air compressor below the minimum capacity control.

  Accordingly, when the compressor inverter 1 is damaged due to lightning or the like, the one-touch type power circuit change-over switch 13 causes the power circuit change-over switch 13 to turn off the cut-off switch 12A of the power cable 5A and the cut-off switch of the power cable 5B. 12B is cut off, and the cut-off switch 12C of the power cable 5C is connected, whereby the air compressor 2 is directly connected to the three-phase AC power source 9 by the power cable 5C.

  Therefore, the operation of the air compressor 2 can be continued, and the damaged post-installation inverter 1 for the compressor can be repaired without hindering the manufacturing process. In addition, the provision of the spare retrofit inverter 1 for the compressor makes it possible to connect a new retrofit inverter 1 for the compressor without stopping the operation of the air compressor 2.

  In the retrofitting inverter for a compressor according to the present invention having the above-described configuration, since a shut-off switch is inserted in the power cable before and after the retrofitting inverter, even if the inverter breaks, it can be immediately switched to the original start-up system, and the factory operation It will not interfere with.

  In addition, since it can be easily retrofitted to an existing air compressor, an air compressor with a long service life can sufficiently store surplus funds by saving energy by the time of replacement.

It is a block circuit diagram which shows an example of the retrofit inverter for compressors to which this invention is applied. It is a driving | operation switching circuit diagram of the retrofit inverter for compressors to which invention is applied.

Explanation of symbols

1 Inverter for compressor 2 Air compressor 3 Star delta start panel 4 Delta magnet switch 5A, 5B, 5C Power cable 6 Air tank 7 Pressure sensor 8 Inverter panel 9 Three-phase AC power supply 10A Output terminal 10B Input terminal 11 Bypass circuit 12A, 12B , 12C Shut-off switch 13 Power circuit switch 14 Compressor operation switch 15 Electric motor 16 Discharge piping

Claims (2)

In the inverter connected between the electric motor drive air compressor and the three-phase power supply by a power cable,
A bypass circuit that connects the three-phase power source and the electric motor-driven air compressor without going through the inverter;
A cutoff switch provided between the electric motor-driven air compressor and inverter, the inverter and the three-phase power source, and the bypass circuit;
When the inverter is activated, the shut-off switch between the bypass circuits is turned OFF, and when the inverter fails, the shut-off switch between the bypass circuits is turned ON, and the electric motor-driven air compressor and inverter and the inverter and the three-phase power source are shut off. A retrofitting inverter for a compressor, comprising a power circuit switching switch for turning off the switch. The retrofitting inverter for a compressor according to claim 1, wherein a star delta starting board installed in the electric motor drive air compressor and the inverter are connected by a power cable.

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