JPS6349456B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an inverter device for driving an alternating current load such as an alternating current motor, and particularly relates to an improvement in an overload protection circuit of the device.

[Prior art]

A conventional device of this type is shown in FIG. 1 is an AC power supply connected to a converter 2 composed of a rectifier 3; 4 is a capacitor connected to the converter 2 and connected to an inverter 6 through a current detector 5; 7 is an AC motor connected to the inverter 6; 8 is an AC power supply connected to the converter 2; A circuit 10 that interrupts the first ignition signal 9
11 is the output of the cutoff circuit 10, which is the second ignition signal supplied to the inverter 6; 12 is the output of the current detector 5, which is the output of the amplifier 1;
A current detection signal is input to 3, and 14 is an amplifier 13.
16 is the output of the first overload discrimination circuit 15 and is an overload cutoff signal inputted to the cutoff circuit 10.

Next, the operation will be explained. Converter 2 is
A power source 1 which is an alternating current is rectified by a rectifier 3 to become a direct current. Capacitor 4 balances the direct current obtained by converter 2 and supplies it to inverter 6 . The inverter 6 receives the PWM-modulated signal by the second ignition signal 11, and sequentially starts and extinguishes the electric valves of each arm, and supplies variable frequency, variable voltage AC power to the AC motor 7, which is an AC load. is supplied to drive the AC motor 7 at variable speed. The control circuit 8 is
A PWM modulated first firing signal 9 is output.
During normal operation, that is, when the overload cutoff signal 16 is not output, the cutoff circuit 10 outputs the first firing signal 9 as it is as the second firing signal 11 (i.e., when the overload cutoff signal 16 is not output). ), when the overload cutoff signal 16 is output, the second ignition signal 11 outputs a signal to extinguish the electric valve of the inverter 6 regardless of the first ignition signal, It works to cut off the power supply to the load. Here, the current detector 5
detects the current supplied to the inverter 6 and inputs its magnitude to the amplifier 13 as a current detection signal 12. The amplifier 13 amplifies the current detection signal 12 and inputs it as a current signal 14 to the overload determination circuit 15 . That is, the inverter output current is current signal 1
This corresponds to 4. Overload discrimination circuit 15
has an inverse time characteristic as shown in Figure 2,
In other words, the overload cutoff signal 16 is not output when the first rated current is less than 17, which is the rating of this inverter device, but the overload state continues where a current equal to or higher than the first rated current 17 continues to flow for a predetermined period of time or more. After a period of time corresponding to the magnitude of the current, the converter 2, capacitor 4, inverter 6, and AC motor 7
An overload cutoff signal 16 is output to the cutoff circuit 10 for protection such as the above. When this overload cutoff signal 16 is output, the cutoff circuit 10 outputs a signal to the inverter 6 to extinguish the electric valve of the inverter 6, and the inverter 6 operates to stop supplying power to the load.

Since the overload protection circuit of a conventional inverter device is configured as described above, the first rated current 17 is determined based on the case where the power source 1 is three-phase AC, and the converter 2 and smoothing capacitor 4 are designed. In an inverter device, when single-phase AC is used as the power supply 1, changing the converter 2 and smoothing capacitor 4 from three-phase to single-phase causes the current to increase and exceed the design value, so the rated current is reduced to three-phase. It is necessary to use the current at a lower current than the first rated current at the time of phase AC input, and below the second rated current at the time of single-phase AC input so that the current of converter 2 and smoothing capacitor 4 is within the design value. The load protection circuit 15 has a protection characteristic at the inverse limit based on the first rated current during three-phase AC input, so it cannot protect the converter 2 and smoothing capacitor 4 from overload during single-phase input. It was hot.

[Summary of the invention]

This invention was made to eliminate the drawbacks of the conventional ones as described above, and has an overload protection means for three-phase input and an overload protection means for single-phase input, and has an overload protection means for three-phase input. By using different overload protection means depending on the result of determining whether the input is phase or single phase, even if an inverter device whose converter, smoothing capacitor, etc. are designed based on three-phase input is used with single-phase input, the converter will be protected from overload. The purpose of this invention is to protect smoothing capacitors and provide a versatile and highly reliable inverter device.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 3 to 5. That is, in Fig. 3, 18 is a first overload discrimination circuit which is an overload protection means for three-phase input, and is set based on the first rated current 17 during three-phase input as shown by A in Fig. 4. It has an anti-time characteristic. In other words, this circuit 18 does not output the overload cutoff signal 16 when the rated current is less than 17 during three-phase input;
If an overload condition continues in which the above current flows for more than a predetermined time, the converter 2, capacitor 4, inverter 6,
An overload breaking current 16 is output to the breaking circuit 10 in order to protect the AC motor 7 and the like. 19
is a second overload discrimination circuit which is an overload protection means for single-phase input, and has an inverse time characteristic set based on the second rated current 20 at the time of single-phase input as shown by B in Fig. 4. have. In other words, this circuit 19
The circuit provides protection at a lower load than the first overload discrimination circuit 18, and does not output the overload cutoff signal 16 when the rated current is less than 20 during single-phase input, but when the rated current is 20 or more When an overload state in which current continues to flow for a predetermined period of time or more continues, an overload breaking current 16 is output to the breaking circuit 10 after a period of time corresponding to the magnitude of the current has passed.

Note that the first and second overload determination circuits 18, 1
9 can use a well-known circuit and can be understood very easily without a detailed explanation, so its details will be omitted. Further, 21 is a first contact inserted in the path between the amplifier 13 and the first overload discrimination circuit 18, and 22 is the first contact inserted between the amplifier 13 and the second overload discrimination circuit 19. The second contact 23 inserted in the path is a single-phase/three-phase input discrimination circuit which is a single-phase/three-phase input discriminating means for discriminating whether the AC power supply 1 is a single-phase input or a three-phase input. At the time of input, a three-phase signal 24 that closes the first contact 21 is output, and at the time of single-phase input, a single-phase signal 25 that closes the second contact 22 is output. This single-phase/three-phase input discrimination circuit 23
It is configured as shown in the figure.

That is, in FIG. 5, the isolation transformer 23A is
The line voltage is isolated and detected, and the logic circuit, i.e.
It works to convert the voltage to the operating level of the AND circuit 23B and OR circuit 23C. Here, a rectifier 23D on the output side of the isolation transformer 23A, a capacitor 2
3E rectifies and smoothes the insulated step-down line voltage, and provides a single-phase discrimination circuit 23F and a three-phase discrimination circuit 23G, respectively.
Output to.

The single-phase discrimination circuit 23F is composed of an OR circuit 23, a CAND circuit 23H, and a NOT circuit 23I.
If a voltage is applied between any one of the lines RS, S-T, and TR (that is, when the power source is single-phase), a single-phase signal 25 is output. In addition, the three-phase discrimination circuit 23G
It is composed of an AND circuit 23B, and R-S, S
When voltage is applied between all the lines -T and TR (that is, when the power supply is three-phase), a three-phase signal 24 is output. Note that the AND circuit 23H and the NOT circuit 23I function to prevent the single-phase discrimination circuit 23K from outputting the single-phase signal 25 when there is a three-phase input.

The single-phase/three-phase input discrimination circuit 23 is configured as described above.

Note that the other configurations are the same as those of the conventional one, so explanations will be omitted.

Next, the operation will be explained. Converter 2 is
A power supply 2 which is an alternating current is rectified by a rectifier 3 to become a direct current. Capacitor 4 smoothes the DC obtained by converter 2 and supplies it to inverter 6 . The inverter 6 receives the PWM modulated signal by the second ignition signal 11 and sequentially starts and extinguishes the electric valves of each arm, and supplies variable frequency, variable voltage AC power to the AC motor 7, which is an AC load. and drives the AC motor 7 at variable speed. The control circuit 8 is
A PWM modulated first firing signal 9 is output.
During normal operation, that is, when the overload cutoff signal 16 is not output, the cutoff circuit 10 outputs the first ignition signal 9 as it is as the second ignition signal 11 (i.e., when the overload cutoff signal 16 is not output). ), when the overload cutoff signal 16 is output, the second ignition signal 1
1 outputs a signal to extinguish the electric valve of the inverter 6 regardless of the first ignition signal 9, and functions to cut off the supply of power to the load. Here, current detector 1
5 detects the current supplied to the inverter 6;
The amplifier 13 uses the magnitude as the current detection signal 12.
Enter. The amplifier 13 amplifies the current detection signal 12 and outputs it as a current signal 14. The operation up to this point is similar to the conventional one.

On the other hand, the single-phase/three-phase input discrimination circuit 23 discriminates whether the input power supply 1 is single-phase or three-phase, and if the result is three-phase, it outputs a three-phase signal 24, and if it is single-phase, it outputs a single-phase signal 24. Outputs 25. When the three-phase signal 24 is output, the first contact 21 is closed and the current signal 14 is output.
is input to the first overload discrimination circuit 18 and the single-phase signal 25 is output, the second contact 22 is closed and the current signal 14 is input to the second overload discrimination circuit 1.
9 is input. When the input power source 1 is three-phase, the above-mentioned first overload discrimination circuit 18, that is, the first
It has an inverse time limit characteristic set based on the rated current 17 of When an overload condition in which current continues to flow for a predetermined period of time or longer continues, converter 2, after a period of time corresponding to the magnitude of the current,
Circuit 1 cuts off overload breaking current 16 to protect capacitor 4, inverter 6, AC motor 7, etc.
The first overload discriminating circuit 18 that outputs 0 operates. In addition, when the input power source 1 is single-phase, the second overload discrimination circuit 19 described above, that is, the counter current set based on the second rated current 20 at the time of single-phase input, as shown by B in FIG. It has a time-limiting characteristic, and does not output the overload cutoff signal 16 when the rated current is less than 20 during single-phase input, but when the rated current 2
When an overload state in which a current of 0 or more continues to flow for a predetermined time or longer continues, a second overload determination circuit 19 outputs an overload cutoff current 16 to the cutoff circuit 10 after a time period corresponding to the magnitude of the current has passed. works. If an overload condition continues in which a current higher than the rated current continues to flow for a predetermined time or more, the first or second overload discrimination circuit 18 or 19 interrupts the overload after a time corresponding to the magnitude of the current. Current 16 is cutoff circuit 1
Output to 0. When this overload cutoff signal 16 is output, the cutoff circuit 10 outputs a signal to the inverter 6 to extinguish the electric valve of the inverter 6, and the inverter 6 works to stop supplying power to the load. .

Note that although the above embodiments have described a PWM inverter, a PAM inverter may also be used.

Further, in the above embodiment, a diode is used as the element of the converter, but any rectifying element may be used. Similarly, the elements of the inverter 6 may be any electric valve such as a transistor.

Further, in the above embodiment, three-phase input and single-phase input are automatically discriminated by the single-phase/three-phase input discriminating circuit, but the operator may manually input the discrimination result.

In addition, in the above embodiment, two types of overload discrimination circuits are prepared and switched between single-phase and three-phase to provide overload protection with different protection characteristics.However, the protection characteristics can be switched between single-phase and three-phase. If so, other methods may be used, such as using one type of overload discrimination circuit and changing the gain of the amplifier 13, for example.

Furthermore, in the above embodiment, overload was detected by detecting the DC bus current, but any device that can detect overload such as inverter output current, converter input current, capacitor inflow and outflow current, etc. can be used. It's okay to be hot.

〔Effect of the invention〕

As described above, according to the present invention, the first overload protection means for three-phase input and the second overload protection means for single-phase input are provided, and whether the input power source is three-phase or single-phase, By using different overload protection methods based on the results of determining the
Even if an inverter device designed with a smoothing capacitor etc. is used with single-phase input, the converter,
This has the effect that the smoothing capacitor can be protected and a versatile and highly reliable inverter device can be obtained.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional inverter device, Figure 2
The figure shows the overload protection characteristics of a conventional inverter device.
FIG. 3 is a block diagram of an inverter device according to an embodiment of the present invention, FIG. 4 is an overload protection characteristic diagram of an inverter device according to an embodiment of the present invention, and FIG. 5 is an inverter device according to an embodiment of the present invention. single phase/
FIG. 3 is a diagram showing details of a three-phase input discrimination circuit. 1 is a power supply, 2 is a converter, 3 is a rectifier, 4 is a capacitor, 5 is a current detector, 6 is an inverter,
7 is an AC motor, 8 is a control circuit, 9 is a first ignition signal, 10 is a cutoff circuit, 11 is a second ignition signal,
12 is a current detection signal, 13 is an amplifier, 14 is a current signal, 16 is an overload cutoff signal, 17 is a first rated current, 18 is a first overload discrimination circuit, 19 is a second
overload determination circuit, 20 is the second rated current, 21
is the first contact, 22 is the second contact, 23 is single phase/
A three-phase input discrimination circuit, 24 is a three-phase signal, and 25 is a single-phase signal. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In an inverter device that converts an AC power source, which is an input power source, into DC power, inversely converts this into AC power using an inverter, and drives an AC load with this AC power, it is possible to determine whether the AC power source is single-phase or three-phase. a single-phase/three-phase input discriminating means for discriminating, a three-phase input overload protection means for stopping the operation of the inverter using an inverse time characteristic when the AC power source is three-phase; and a single-phase input overload protection means that stops the operation of the inverter using an inverse time limit characteristic, and performs overload protection at a lower load than the three-phase input overload protection means, Based on the determination result of the phase input determining means, when the AC power source is three-phase, a three-phase input overload protection means is activated, and when the AC power source is single-phase, the single-phase input overload protection means is activated. An inverter device characterized by: