JPH03226297A - Controller for air-conditioner - Google Patents

Abstract

PURPOSE:To enable continuous operation even when the frequency/voltage characteristic is set at the maximum efficiency point or even under overload conditions by performing control such that overload of an induction motor is judged based on the output from a power factor comparing means and the voltage of an induction motor is boosted while the frequency thereof is lowered. CONSTITUTION:The controller for air-conditioner comprises means 14 for detecting the power factor of an induction motor 6, means 15 for comparing thus detected power factor with an arbitrarily set power factor, and means 16 for judging overload of the induction motor 6 based on the output from the means 15 and boosting the voltage of the induction motor 6 while lowering the frequency thereof. Overload of the induction motor 6 causes significant variation of power factor, and thereby the overload detecting means 16 controls the voltage and frequency of the induction motor 6. Consequently, current of the induction motor is prevented from increasing under overload conditions even if the frequency/voltage characteristics of the induction motor 6 are set at maximum efficiency points.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a control device for an air conditioner, and particularly to a control device for an air conditioner.

The present invention relates to a control device for an inverter device that performs variable speed control of an induction motor of a compressor.

[Prior Art] FIG. 7 is a configuration diagram showing a control circuit of a conventional inverter device disclosed in, for example, Japanese Unexamined Patent Publication No. 1-190293.

In the figure, (1) is an AC power supply, (2) is a converter unit that converts AC power to DC, (3) is a smoothing capacitor, and (4) is an inverter unit that converts DC power to AC of an arbitrary voltage frequency. These elements constitute an inverter device (5). (6) is an induction motor that is the load of the inverter device, and (7) is an inverter control device, which is a microcomputer (hereinafter referred to as "microcomputer") that calculates a signal of an arbitrary set frequency to the inverter section (4) and outputs voltage and frequency data. (referred to as a microcomputer) (8) and a DC/DC converter collar (9) that converts the DC v1 input from the inverter W (5) into DC power for the inverter control circuit.
and a V/F converter circuit (1'O) that converts the voltage of the DC power supply into a frequency. (11) is a current transformer that detects the negative current of the induction motor (6). (Step 2) is an inverter device! (5) This is a data storage unit that stores data of the V/F pattern of the output voltage and output frequency.

Next, the operation will be explained. The V/F converter circuit (10) constitutes a voltage discrimination circuit for the DC power supply voltage Vl supplied to the inverter section (4).

Fluctuations in the power supply voltage v1 are determined by comparing the output frequency value with an arbitrary set reference value.

For example, when the voltage of the AC power supply (1) decreases when the inverter device (5) is operating under a steady load.

The voltage v1 supplied to the inverter section (4) also decreases, and the current flowing to the induction motor (6) increases rapidly.

At this time, the voltage output from the DC/DC converter collar (9) into which the voltage Vl is inputted to the V/F converter circuit (10) also decreases. V/F converter circuit (10)
When the input voltage decreases, the frequency output from the V/F converter circuit (lO) also decreases, due to the configuration that has a linear function characteristic, so that the output frequency also decreases.

Here, the voltage V output to the induction motor (6) is set to V=*VO*FO/Fx [V] K: Correction function FO: Reference vO for voltage v1 that can be placed during steady load:
Each frequency frequency quasi-voltage Fx: It can be expressed by the formula of the output frequency value of the V/F converter circuit under each condition, and the above V/F converter circuit (
10) Even if the output frequency decreases, that is, the voltage of the DC power supply supplied to the inverter section (4) decreases, a constant output frequency and voltage can always be supplied to the induction motor (6). .

[Problems to be Solved by the Invention] Conventional air conditioner control devices are configured as described above, so that the characteristics of the frequency and voltage output to the induction motor can be adjusted to operate a load such as an air conditioner. Since the characteristics differ between the maximum efficiency point and the overload condition, if the characteristics are matched to the maximum efficiency point, the current flowing to the induction motor increases under the overload condition, and the protection function in the inverter device is activated. Since the control is stopped, continuous operation is not possible. Furthermore, when the characteristics are matched under overload conditions, there is a first problem in that the efficiency deviates from the maximum efficiency point under steady load.

Furthermore, in conventional air conditioner control devices, a PWM (pulse width modulation) method, which is generally said to have good responsiveness, is used as a signal for driving an induction motor of a compressor. However, in the case of the PWM method, the reference signal (frequency) that generates the PWM signal uses a frequency of 1 to 3 KHz, which is particularly easy to hear among the audible frequency bands, so the second problem is that it generates more noise than the outdoor unit of an air conditioner. There was a problem.

The first invention of the present invention was made to solve the first problem mentioned above, and even if the frequency and voltage characteristics output to the induction motor are set to the highest efficiency point and the operation is performed, the overload condition The purpose of the present invention is to provide a control device for an air conditioner that can operate continuously even when the air conditioner is in use.

A second aspect of the present invention has been made to solve the second problem, and aims to provide an air conditioner control device that reduces noise generated from an outdoor unit. .

[Means for Solving the Problems] A control device for an air conditioner according to a first aspect of the present invention includes:
a power factor detection means for detecting a power factor value of a load of an induction motor;
A power factor comparison means for comparing the power factor value detected by this means with an arbitrarily set power factor value, and an overload of the induction motor is determined according to the output of the power factor comparison means, and the voltage of the induction motor is determined. The apparatus is provided with overload determination means for controlling the frequency to increase and decrease the frequency.

The air conditioner control device according to the second invention of the present invention includes:
an operating state determining means for determining whether the operating state of the induction motor is a constant frequency operating state or a one frequency change operating state; and depending on the determination by this means, the output voltage of the inverter section is controlled by a PAM method or by a PWM method. The control system is provided with control method switching means for switching the control method.

[Function] In the first aspect of the present invention, when an overload occurs on the induction motor when the induction motor is operated so that the frequency/voltage characteristics output from the inverter device are at the highest efficiency point, Since the power factor of an induction motor changes significantly,
Accordingly, the output of the power factor comparing means changes, and the overload determining means controls the voltage of the induction motor to increase and the frequency to decrease, so that the induction motor is continuously driven even under overload.

In the second aspect of the invention, the frequency output from the inverter device changes from when the induction motor is started until it reaches a constant rotational speed.

The operating state determining means determines that the operating state is frequency change, and the control method switching means switches the inverter device to PW.
The control is switched to the M method, and the induction motor is controlled by the PWM method with good responsiveness. When the induction motor reaches a constant rotational speed and there is no change in the frequency output from the inverter device, the operating state determining means determines that the operating state is constant frequency, and the control method switching means changes the inverter device to the PAM (Pulse Amplitude Modulation) method. The induction motor is controlled by the PAM method, which has poor response but does not include a reference signal in the audible frequency band, and noise from the outdoor unit is reduced.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a circuit configuration diagram showing one embodiment of the first invention of the present invention, and FIG.
Figure 3 is a characteristic diagram showing the efficiency and power factor, and Figure 3 is a characteristic diagram showing the output voltage and frequency to the induction motor in Figure 1. In Figure 1, (1) is an AC power supply, (2) is a converter section, ( 3) is a smoothing capacitor, (4) is an inverter section, (5) is an inverter device, (6) is an induction motor for a compressor, and (7) is an inverter control device. It is similar. (13) is an inverter control device (
7) is a voltage/frequency determining means for calculating and determining the output voltage and frequency of the inverter device (5) according to the input data by a built-in microcomputer, and outputting it to the inverter section (4); (14) is the inverter section; The phase difference between the drive voltage signal of the transistor detected from the induction motor (6) and the voltage waveform signal applied to the inverter section (4)
) power factor detection means for detecting the power factor value, and (15) power factor comparison means for comparing the power factor value detected by this means (14) with a predetermined set power factor value.

(16) determines whether the induction motor (6) is overloaded according to the output of this means (15), and if it is overloaded, increases the output voltage value from the voltage/frequency determination means (13), and increases the output frequency. This is overload determining means that controls the value to decrease.

Next, the operation will be explained. Now, power factor detection means (14)
The power factor detected by the induction motor (6) in Fig. 2 is
Inverter device f (5)
It is assumed that the output voltage of the induction motor (6
) during normal operation, that is, for normal load torque, the voltage and
It is assumed that the frequency characteristics are on the solid line in FIG. 3, and that the device is operating at points F and V therein. At this time, when the load condition shifts to overload, slippage increases due to the characteristics of the induction motor (6). As the slip increases, the efficiency decreases, and the power factor shifts from point A to point D in Fig. 2. This is detected by the power factor detection means (14) of the inverter control device (7), and the power factor is detected by the power factor detection means (14) of the inverter controller (7). A signal indicating that the power factor has increased, that is, the load on the induction motor (6) has increased, is output from the factor comparing means (15), and in response to this signal, the overload determining means (16) changes the voltage to F in FIG. Arbitrary set increment d from point V to vl
(v) is increased to increase the torque of the induction motor (6) and prevent an increase in current, and furthermore, the frequency is arbitrarily changed from F to F according to the characteristics of the dashed line according to the torque at this time. The setting decrement d (Hz) is reduced to prevent the induction motor (6) from increasing.

FIG. 4 is a circuit configuration diagram showing an embodiment of the second invention of the present invention, FIG. 5 is a time chart showing a variable speed control pattern for explaining the operation of this embodiment, and FIG. 6 is a diagram showing this embodiment. 3 is a flowchart illustrating an example control operation. In FIG. 4, (1) to (7).

(13) shows the same or equivalent part as the embodiment shown in FIG.
) is different from that shown in Fig. 1, and is composed of a bridge made of thyristors whose energization angle can be set to an arbitrary value. (17)～
(20) is each means executed by the microcomputer built in the inverter control device (7), and (17) is the operation state of the induction motor (6) that is set to constant frequency operation based on information from the voltage frequency determining means (13). Is it the state?

Operating state determination means (
18) controls the voltage of the induction motor (6) by applying to the inverter section (4) a PWM signal which is a width-modulated pulse signal of the reference signal frequency according to the voltage and frequency data from the voltage frequency determining means (13). , P which controls the frequency
The WM control means (19) is a voltage frequency determining means (13).
) The energization angle of the thyristor of the converter section (2) is controlled so as to output a DC voltage of a magnitude according to the voltage data from the inverter section (4) according to the frequency data from the voltage frequency determining means (13). P to control the output shoulder wave number of
AM control means.

(20) is based on the output of the driving state determining means (17),
This is a control method switching means for switching which of the PWM control means (18) and the PAM control means (19) is operated.

In FIG. 5, the horizontal axis t indicates time, the vertical axis F indicates the frequency of the induction motor (6), and ■ indicates a period in which the frequency of the induction motor (6) that drives the compressor increases from 0 and is accelerated; T.I.
Tn is the section where the frequency reaches the highest frequency and the capacity of the air conditioner is maximized, Tn is the section where the room in which the air conditioner is used reaches the target temperature and humidity, the capacity is reduced, and the induction motor (6) is decelerated. This is the section where capacity is minimized and economical operation is carried out.

Next, the operation will be explained using the flowchart shown in FIG.

First, in step (21), for example, when the frequency is set in the section ■, the current frequency value F is larger than the previous frequency value F, because it is in the acceleration region, and it is in the frequency change driving state. (driving state determination means (17)
)) Proceed to step (22) (control method switching means (2)
0)), the PWM waveform of the reference signal frequency is calculated, and in step (26) the data is sent to the inverter section (4).
(PWM control means (18)), the frequency increases and reaches the maximum frequency and enters the ■ section, Fl and F, □
are the same value and from step (21) to step (23)
(control method switching means (20)), PWM waveform calculation using the reference signal frequency is not performed, but PAM waveform calculation is performed, and in step (24), the voltage data of the thyristor of the converter section (2) is calculated. The energization angle is calculated, and in step (25), a signal of the energization angle is output to the converter section (2), and in step (26), the frequency data of the PAM waveform is output to the inverter section (4).
M@Gotsu (19)). The operations in the next four sections are performed in the same manner as in section (■), and the operations in section (2) are performed in the same manner as in section (■).

In this way, in operating conditions where the voltage and frequency change significantly but the operating period under such conditions is relatively short, PWM operation has good responsiveness, but in operating conditions where the voltage and frequency are stable and continues for a relatively long time, PWM operation has good response. Although the quality is bad, the reference signal frequency (1~3E
KH13) PAM operation without audio frequency signals is carried out, resulting in a significant reduction in noise without significantly impairing overall responsiveness.

[Effects of the Invention] As described above, according to the first aspect of the present invention, there is provided a power factor detection means for detecting a power factor value of a load of an induction motor, and a power factor value detected by the means and an arbitrary setting. a power factor comparison means for comparing the power factor value of the induction motor with the power factor value of the induction motor; Since a load discrimination means is provided, even if the frequency voltage characteristic output to the induction motor is set to the highest efficiency point and the induction motor is operated, the current of the induction motor is prevented from increasing during overload conditions, and continuous operation is prevented. This has the effect of providing a control device for an air conditioner that is possible.

Further, according to the second aspect of the present invention, there is provided an operating state determining means for determining whether the operating state of the induction motor is a constant frequency operating state or a frequency varying operating state, and an output of the inverter section according to the determination by the means. Since a control method switching means for switching whether the voltage is controlled by the PAM method or the PWM method is provided, the noise generated by the induction motor as a whole is significantly reduced without significantly impairing the control response of the induction motor. This has the effect of providing a control device for an air conditioner that reduces costs.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram showing an embodiment of the first invention of the present invention, Fig. 2 is a characteristic diagram showing torque, efficiency, and power factor with respect to slippage of the induction motor shown in Fig. Fig. 1 is a characteristic diagram showing the output voltage and frequency to the induction motor, Fig. 4 is a circuit configuration diagram showing an embodiment of the second invention of the present invention, and Fig. 5 is for explaining the operation of this embodiment. FIG. 6 is a flowchart showing the control operation of this embodiment, and FIG. 7 is a configuration diagram showing a control circuit of a conventional inverter device. In the figure, (2) is the converter section, (3) is the smoothing capacitor, (4) is the inverter section, (5) is the inverter device, (6) is the induction motor, (7) is the inverter control device, and (13) is the inverter section. (14) is a power factor detection means, (15) is a power factor comparison means, (16) is an overload determination means, (17) is an operating state determination means, (18) is a P
WM control means, (19) is PAM control means, (20
) is a control method switching means. The same reference numerals in the figures indicate the same or corresponding parts. Fig. 2: Converter section 4: Inverter section 5: Inverter device 6: Induction motor 7: Inverter control device Fig. Fig. 4 Fig. Fig. Fig. 4

Claims (2)

[Claims] (1) An inverter that has a converter section that converts input alternating current to direct current, and an inverter section that converts this direct current back to alternating current of an arbitrary frequency, and outputs a variable frequency from this inverter section to the induction motor of the compressor. An air conditioner control device comprising an inverter control device that controls the output voltage and frequency of the inverter section to a predetermined value, comprising: a power factor detection means for detecting a power factor value of the load of the induction motor; power factor comparison means for comparing the power factor value detected by the means with an arbitrarily set power factor value; and according to the output of the power factor comparison means, it is determined whether the induction motor is overloaded and the voltage of the induction motor is increased. 1. A control device for an air conditioner, comprising: overload determining means for controlling the frequency to decrease. (2) An inverter that has a converter section that converts input alternating current into direct current, and an inverter section that converts this direct current back into alternating current of an arbitrary frequency, and outputs a variable frequency from this inverter section to the induction motor of the compressor. In an air conditioner control device comprising an inverter control device that controls the output voltage and frequency of the inverter unit to a predetermined value, the induction motor is configured to determine whether the induction motor is in a constant frequency operation state or a frequency varying operation state. The present invention is characterized by being provided with an operating state determining means for making a determination, and a control method switching means for switching whether the output voltage of the inverter section is controlled by a PAM method or a PWM method depending on the determination by the means. Air conditioner control device.