JPH02214497A - Inverter device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an air conditioner having an inverter device for variable speed control of an electric motor.

[Conventional technology]

FIG. 8 is a circuit configuration diagram showing an inverter device t disclosed in Japanese Patent Application No. 61-430230, for example, for variable speed control of an induction motor for a compressor of an air conditioner. In the figure, (!) is an AC power supply, and C2) is an AC power supply (
1) A converter section that converts the AC input from 1) into DC, +3) Fi smoothing capacitor.

(4) An inverter section that converts the smoothed direct current back into alternating current of the same arbitrary wave number, and these elements constitute a frequency converter (5). (7) is a control circuit section of the frequency converter (5) and constitutes an overload region determining means. That is, this control circuit section (7) is equipped with a comparator (5I) that compares the detection circuit of the input AC voltage applied to the inverter device (5) and the detected value with a reference value. ) is used to determine the overload area.

I is a microcomputer (hereinafter referred to as microcomputer) which outputs an arbitrary frequency command to the inverter section (4).

Is Figure 9 induction? ! Frequency converter that drives the electric motor 6) [
F5) v-? This is a diagram showing pattern data. Curve 1 in the diagram is data in the normal steady load area, and curve 9 is data in the normal steady load area.
This is dedicated data for the Fi overload area.

The characteristics of this overload region are that the voltage (VM N2) in the low output data is the voltage fVM N1 in the steady load region.
) compared to high (has become. and.

Based on the flexibility of these data, the microcomputer a4 drives the inverter section.

If the inverter section (4) is operating in a steady load region (1), for example, if the induction 111 (inductor 16) is for an air conditioner compressor, if the outside air temperature changes and it moves into the overload region, Induction'i! The R current of the motive force (6) increases and the voltage applied to the frequency changer 41I device (5) gradually decreases. At this time, the comparator (5
1), a detection signal corresponding to the voltage applied to the frequency conversion device #(5) is inputted, and is compared with the contrast reference voltage signal. Here, when the mark 1ya voltage decreases, the comparator (5
Assuming that an H''' (high level) signal is output from I), the microcomputer α to which the H' signal is input from the comparator (5I) will be connected to the dedicated A signal with the v-p characteristic is output to the wave number converter ?+51.As a result, a higher voltage than the previous time is output to the induction motor/61, and the current flowing to the induction IE motor 6) is reduced.

On the other hand, if a signal of "L" (low level) is output from comparison 1 (51), it is determined that the load is in the steady load region.

A signal with a normal v-F characteristic shown by curve A in FIG. 9 is output from the microcomputer I to the frequency converter 1 (51). The induction motor (
6) This prevents the current from increasing and causing continued operation to stop.

[Problem to be solved by the invention]

However, in the case of the air conditioner control device as described above, it has the advantage of being able to suppress the current flowing to the induction motor by changing the output turn of the inverter device when it enters a certain overload range. However, if a sudden load change occurs between the steady load area and the overload area,
Alternatively, if load fluctuations that result in transient load conditions occur, the induction motor must be stopped because a current that exceeds the allowable value flows through the semiconductor elements used in the inverter section that cannot be followed by the above control. The problem is that the induction motor cannot be operated continuously.

The problem is that a ninth dedicated circuit (not shown) must be provided to prevent the breaker from operating.

This invention was made to solve these problems, and even when sudden load fluctuations or transient load fluctuations occur, the induction motor does not stop F.
Another object of the present invention is to provide a control device that can be constructed at low cost by using existing circuits in air conditioners.

[Means to solve the problem]

The inverter device according to the present invention includes a converter section that converts alternating current into direct current, an inverter section that converts the direct current back into pseudo alternating current, and a detection means that detects the input current of the converter section or the inverter section.

a setting means for setting a permissible pus flow of the inverter section;
A first comparison means for comparing the input current from the detection means with the maximum allowable current, and a control means for controlling the output of the inverter section according to the output of the comparison means, wherein the control means The output of the inverter section is controlled in accordance with the output of a second comparison means that compares the change value of the input current when the output of the inverter section is changed by a predetermined amount with a preset change reference value. It is something.

[Function] The inverter device of the present invention compares the input current of the converter section or the inverter section with the maximum allowable current of the inverter section, and also calculates in advance the change in the input current by one shift when the output of the inverter section is changed by a predetermined amount. The output of the inverter section is controlled by comparing the set change reference skin.

〔Example〕

FIG. 1 shows one embodiment of the present invention, and the drawing will be explained. In the figure, fl) to (6) are all the same as the conventional device.

(7) is an input current detection circuit, (8) is a current transformer that converts the input current of the air conditioner into voltage, (9) is a load resistance for regulating the output voltage of the current transformer (8), O1#i The next diode (II) converts the AC voltage output from the current transformer into DC.

113 is a voltage dividing resistor, fIm is a capacitor for smoothing the divided voltage, and a current transformer (8),
Resistance f9), til+, +13. Diode Q1
．． :f:/Capacitor 01 constitutes an input current detection path. I is a microcomputer that outputs an arbitrary frequency command to the inverter section (4). The microcontroller 41 has a built-in tth analog/digital port (hereinafter referred to as A/D port) that inputs the voltage from the current transformer.

Figure 2a shows the frequency of the compressor induction of the air conditioner = IIT 16) and the input '! to the 0 frequency political converter + II f5)! It is a t-diagram showing the characteristics of the flow. In the figure,
Type 1 shows the characteristics at normal rated load, Type 2 shows the characteristics at overload, and Type 3 shows the characteristics at light load.

Figure 2b shows the induction motor (6) for the compressor of the air conditioner.
FIG. 3 is a diagram showing the relationship between the voltage at 9 o'clock and the input current to the inverter device with the frequency F fixed at F'1.

The next KIIh operation will be explained using the flowchart shown in FIG.

When the air conditioner is operating under normal conditions,
Even when the frequency of the induction motor (6) is changing, the input current input to the inverter device is controlled in the range from step 2 to step 3 of 2nd a19. Here, 1. For example, in the event of an abnormality when the fan motor of the outdoor unit stops during cooling operation, or the fan motor of the indoor unit stops during heating operation, in step (■1), the maximum allowable current is set. The first comparison means compares the injection current 2, which has previously stored the input current for each same wave number in the heavy load region in the microcontroller No. 70, with the input current 1 currently input to the inverter device t151. Compare by step (
■Move to 5). If work 2 ≧ work 1, step (11
Move on to 2). In step (2), if normal voltage control is being performed, the voltage is being varied, so it is determined. If “N”, the process returns to the initial state.

Also, if “Y”, move to step (■3) and take +1 (v) L step (114) for the current voltage v1.
to move to. Here, if the voltage changes by +1 (Hz) in advance, let f be the change in the setting of the input current value.In step (■4), the input current value 1 after the voltage change and the previous input current value 1 are The absolute value of the difference of -1 is compared with the work f, and if the work f≧l1l-1-11, it is determined that the state is normal and returns to the initial state.If the work f≦1 work1 (1-11), the It is determined that there is an abnormal load condition and the process moves to step (+15).

At step (+15), hold for an arbitrary time (X(13)). By holding the value, it is determined whether it is due to a single-time load fluctuation or an abnormal condition.

If the load is abnormal, the overload judgment is carried out again in step (lL5), and if it is abnormal, the positive voltage of the compressor is manipulated back to control the voltage to 2 ≧ (A1 or less. If 2 ≧ 1, step (■ 8), the voltage applied to the compressor is increased, and in step (+19), the second comparison means is used to control II1-E1-11 to be equal to or less than the specified value.

In this way, the input current value under the overload condition is set according to each output frequency of the inverter device, and -! It was.

By setting the amount of change in the input current value when the frequency changes, the load conditions can be determined using an existing circuit. In addition, by determining an abnormal load, the load current exceeds the current protection level of the semiconductor used in the inverter section (41), which causes the frequency converter (5) to stop.
The induction motor (6) will not be able to continue operating and will not stop.

FIG. 4 is a circuit diagram showing another embodiment of the present invention. Figures 5a and 51:1 show the frequency and voltage '1! of an induction motor for a compressor in another embodiment. It is a reminder of the characteristics of flow. FIG. 6 is a flowchart showing a control method in an embodiment of the pond.

In this embodiment, the output It current of the inverter device, ie.

The purpose is to determine the load conditions of the air conditioner and inverter device by detecting the input current to the induction motor, and a current transformer (8) is connected between the inverter section (4) and the induction motor 16). are doing.

With such a configuration, the same effects as in the seventh embodiment can be obtained, and the induction motor can be operated continuously even if there are load fluctuations.

The @T diagram is a flowchart showing a control method for skipping other examples of regret. In this embodiment, the inverter device and induction motor are stopped after detecting an abnormal load. The monument is designed to prioritize the protection of equipment.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a converter section that converts alternating current into direct current, an inverter section that converts the direct current back into pseudo alternating current, and a detection means that detects the input current of the converter section or the inverter section.

a setting means for setting an allowable firing current of the inverter section;
A first comparison means for comparing the input current from the detection means with the maximum allowable current, and a control means for controlling the output of the inverter section according to the output of the comparison means, wherein the control means The output of the inverter section is controlled in accordance with the output of a second comparison means that compares the change in the input current when the output of the inverter section is changed by a predetermined amount with a preset change reference value. So.

Even if fluctuations in the load of the inverter equipment occur.

This allows the load to continue operating without causing the inverter to stop due to the load current exceeding the maximum allowable current of the inverter.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing an embodiment of the present invention. Fig. 2a is a characteristic diagram showing the relationship between the frequency of the compressor and the input current to the inverter device, and Fig. 2b is a characteristic diagram showing the relationship between the voltage of the compressor and the input current to the inverter device. 3 is a flowchart of the control method, FIG. 4 is an overall configuration diagram showing another embodiment of the present invention, and FIG. 5a is a characteristic diagram showing the relationship between the compressor frequency and A characteristic diagram showing the relationship between the input current to the inverter device, Fig. 5b is a characteristic diagram showing the relationship between the voltage of the compressor and the input current to the inverter device, and Fig. 6 is a flow chart diagram of the control method. FIG. 7 is a flowchart of a control method according to another embodiment of the present invention, FIG. 8 is an overall configuration diagram of a conventional inverter device, and FIG. 9 is a characteristic diagram showing the relationship between voltage and frequency of the compressor. . In the figure, (1) is an AC power supply, and (2) is a converter section. (4) is the inverter section, (7) is the input current detection circuit, (
14 is a microcomputer. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] a converter unit that converts alternating current into direct current; an inverter unit that converts the direct current back into pseudo alternating current; a detection unit that detects the input current of the converter unit or the inverter unit; a setting unit that sets the maximum allowable current of the inverter unit; In the inverter device, the inverter device includes first comparison means for comparing the input current from the detection means and the maximum allowable current, and control means for controlling the output of the inverter section according to the output of the comparison means, wherein the control means The output of the inverter section is controlled in accordance with the output of a second comparison means that compares the change value of the input current when the output of the inverter section is changed by a predetermined amount with a preset change reference value. Inverter device.