JPH08285389A - Air conditioner - Google Patents

Abstract

PURPOSE: To provide an inverter device used in an air conditioner in which an efficiency of the air conditioner is improved under an operation of the air conditioner in a voltage-frequency characteristic suitable for a loaded condition. CONSTITUTION: Enthalpy of a work of a compressor is calculated by an enthalpy calculator 19 on the basis of information of the compressor obtained by a discharging pressure sensor 15, a discharging temperature sensor 16, a suction pressure sensor 17 and a suction temperature sensor 18. A load torque is calculated with a load torque assuming device 2 on the basis of the calculated enthalpy. The most suitable voltage-frequency characteristic is determined by a voltage-frequency characteristic determining device 21 on the basis of the calculated characteristic and then a wave-form generating device 13 outputs a wave-form signal of a wave-form pattern of the most suitable voltage- frequency characteristic from the wave-form memory device 12 storing each of the different wave-form patterns of voltage-frequency characteristic to an inverter device 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner equipped with a control device for controlling a compressor by an inverter.

[0002]

2. Description of the Related Art In recent years, an air conditioner has been used which controls the capacity by increasing or decreasing the number of revolutions of a compressor by using an inverter device which makes a frequency of a power source variable.

As a conventional technique, for example, Japanese Patent Laid-Open No. 1-
There is one disclosed in Japanese Patent Publication No. 200080.

An example of the operation of the prior art will be described below with reference to the drawings. FIG. 9 is a block diagram of a conventional air conditioner, FIG. 10 is a flowchart showing the operation of a waveform generator in the conventional air conditioner, and FIG. 11 is stored in a waveform storage device in the conventional air conditioner. FIG. 3 is a voltage-frequency characteristic diagram that is shown.

In FIG. 9, 1 is a compressor, 2 is a four-way valve,
Reference numeral 3 is an indoor heat exchanger, 4 is a pressure reducing device, and 5 is an outdoor heat exchanger, and these are connected in a ring to form a refrigeration circuit.

Reference numeral 6 is an indoor fan, and 7 is an outdoor fan.
8 is a three-phase AC power supply. Reference numeral 9 is an indoor unit, and 10 is an outdoor unit.

Reference numeral 11 denotes a pressure detector, which outputs a signal A when the suction pressure P of the compressor 1 is P <P1, and P1≤P≤P.
When it is 2, the signal B is output, and when P> P2, the signal C is output.

A waveform storage device 12 stores the waveform patterns A1, B1, C1 of the voltage-frequency characteristics shown in FIG.

Reference numeral 13 is a waveform generator, which is a pressure detector 1.
When the output signal of 1 is A, the waveform pattern A1 is generated, when the signal is B, the waveform pattern B1 is acquired, and when the signal is C, the waveform pattern C1 is acquired from the waveform storage device 12 to generate a waveform.

Reference numeral 14 denotes an inverter device, which receives a waveform signal from the waveform generator 13 and controls the rotation speed of the compressor 1.

The operation of the air conditioner configured as described above will be described below.

First, the operation of the waveform generator 13 will be described with reference to FIG. When the operation of the compressor 1 is started in STEP1, a signal from the pressure detector 11 is fetched in STEP2. Next, in STEP3, it is judged whether the signal fetched is A or not, and if it is A, the operation proceeds to STEP4 to fetch the waveform pattern A1 from the waveform storage device 12.

If the signal is not A in STEP 3, STE
Proceed to P5 to determine if the signal is B. If the signal is B, the process proceeds to STEP 6 to load the waveform pattern B1 from the waveform storage device 12. If the signal is not B in STEP5, the process proceeds to STEP7 and the waveform pattern C1 is loaded from the waveform storage device 12. From the captured waveform pattern, S
A waveform signal is generated in TEP8, and a waveform signal is output in STEP9.

According to the above flow chart, the waveform generator 13 outputs a waveform signal, and the inverter device 14 controls the compressor 1.

[0015]

However, in the above-mentioned conventional structure, the voltage-frequency characteristic is changed by the suction pressure of the compressor 1, so that the voltage-frequency characteristic is determined by the suction pressure of the compressor 1. Therefore, even if the load of the compressor 1 is the same, if the suction pressure varies depending on the outside air temperature, the efficiency deviates from the optimum voltage-frequency characteristic, and the efficiency of the air conditioner deteriorates.

The present invention solves the conventional problems by constantly changing the voltage-frequency characteristics depending on the load of the compressor to maintain the optimum voltage-frequency characteristic of the compressor.
An object is to provide an efficient air conditioner.

[0017]

To achieve this object, an air conditioner of the present invention comprises a compressor whose rotation speed is controlled by an inverter device, and a shell discharge pressure detector for detecting the shell discharge pressure of the compressor. , Shell discharge temperature detector for detecting shell discharge temperature, shell suction pressure detector for detecting shell suction pressure, shell suction temperature detector for detecting shell suction temperature, shell discharge pressure detector and shell discharge temperature A first enthalpy calculator that calculates the work of the compressor from the output signals of the detector, the shell suction pressure detector, and the shell suction temperature detector, and a load that calculates the load torque of the compressor from the output of the first enthalpy calculator A torque estimator,
A voltage-frequency characteristic determining device that determines an optimum voltage-frequency characteristic from the output of the load torque estimator, and a waveform pattern of different voltage-frequency characteristics stored in the voltage-frequency characteristic determining device.
A waveform storage device that outputs a waveform pattern of an optimum voltage-frequency characteristic by the output of the frequency characteristic determination device, and a waveform generation device that generates a waveform from the waveform pattern output by the waveform storage device and outputs the waveform to the inverter device. Has been done.

Further, a compressor whose rotational speed is controlled by an inverter device, a shell discharge temperature detector for detecting the shell discharge temperature of the compressor, a shell suction pressure detector for detecting the shell suction pressure, and a shell suction temperature are shown. Of the shell suction temperature detector, the shell discharge temperature detector, the shell suction pressure detector, and the output signal of the shell suction temperature detector, which calculate the work of the compressor, and the second enthalpy calculator. A load torque estimator that calculates the load torque of the compressor from the output, a voltage-frequency characteristic determination device that determines the optimum voltage-frequency characteristic from the output of the load torque estimator, and waveforms of different voltage-frequency characteristics. A waveform storage device that stores a pattern and outputs a waveform pattern of an optimum voltage-frequency characteristic by the output of the voltage-frequency characteristic determination device; Storage device is more structure as a waveform generator for outputting the generated the inverter waveform from the waveform pattern output.

Further, a compressor whose rotation speed is controlled by an inverter device, a shell discharge pressure detector for detecting a shell discharge pressure of the compressor, a shell discharge temperature detector for detecting a shell discharge temperature, and a shell suction temperature are shown. Of the shell suction temperature detector for detecting, the shell discharge pressure detector, the shell discharge temperature detector, and the output signal of the shell suction temperature detector, the third enthalpy calculator for calculating the work of the compressor, and the third enthalpy calculator A load torque estimator that calculates the load torque of the compressor from the output, a voltage-frequency characteristic determination device that determines the optimum voltage-frequency characteristic from the output of the load torque estimator, and waveforms of different voltage-frequency characteristics. A waveform storage device that stores a pattern and outputs a waveform pattern of an optimum voltage-frequency characteristic by the output of the voltage-frequency characteristic determination device; Storage device is more structure as a waveform generator for outputting the generated the inverter waveform from the waveform pattern output.

[0020]

According to the present invention, the enthalpy of the work of the compressor is calculated from the discharge pressure, discharge temperature, suction pressure, and suction temperature of the compressor, converted into torque, and the voltage corresponding to the converted torque value is obtained. -By outputting a waveform with frequency characteristics, it is possible to operate with optimum voltage-frequency characteristics, so that an efficient air conditioner can be realized.

Further, the enthalpy of the work of the compressor is estimated from the discharge temperature, suction pressure, and suction temperature of the compressor, converted into torque, and a waveform is output with a voltage-frequency characteristic corresponding to the converted torque value. As a result, it is possible to operate with an optimum voltage-frequency characteristic, so that an efficient air conditioner can be realized.

Further, the enthalpy of the work of the compressor is estimated from the discharge pressure, discharge temperature, and suction temperature of the compressor, converted into torque, and a waveform is output with a voltage-frequency characteristic corresponding to the converted torque value. As a result, it is possible to operate with an optimum voltage-frequency characteristic, so that an efficient air conditioner can be realized.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An air conditioner according to an embodiment of the present invention will be described below with reference to the drawings. The same components as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

1, 2, 3 and 4 show a first embodiment of the present invention. 1 is a schematic configuration diagram of an air conditioner according to a first embodiment of the present invention, FIG. 2 is a Mollier diagram of the air conditioner according to the same embodiment, and FIG. 3 is a compressor work load AW and load torque according to the embodiment. Characteristic diagram showing the relationship of T, FIG.
[Fig. 3] is a voltage-frequency characteristic diagram with a load torque T as a parameter.

In FIG. 1, the shell discharge pressure detector 15, the shell discharge temperature detector 16, the shell suction pressure detector 17, and the shell suction temperature detector 18 for detecting the shell discharge pressure of the compressor 1 are the first enthalpy calculation. The first enthalpy calculator 19 is connected to the device 19, calculates the work of the compressor 1 from the output information of each detector, and outputs the work AW of the compressor to the load torque estimator 20. Load torque estimator 2
0 calculates the load torque from the compressor work AW and outputs a signal corresponding to the load torque to the voltage-frequency characteristic determination device 21.
Output to. The voltage-frequency characteristic determining device 21 determines the optimum voltage-frequency characteristic corresponding to the load torque based on the load torque signal, and outputs a signal corresponding to the voltage-frequency characteristic to the waveform storage device 12.

The waveform storage device 12, which stores waveform patterns of different voltage-frequency characteristics, outputs the waveform pattern of the optimum voltage-frequency characteristic to the waveform generator 13 according to the voltage-frequency characteristic signal.

FIG. 2 is a Mollier diagram in which the vertical axis represents pressure and the horizontal axis represents enthalpy. From this Mollier diagram in Figure 2,
The enthalpy E2 can be calculated from the shell discharge pressure P1 and the shell discharge temperature t1 of the compressor 1, and the enthalpy E1 can be calculated from the shell suction pressure P2 and the shell suction temperature t2, that is, the compressor work amount AW from the relationship of AW1 = E2-E1. Can be calculated.

The load torque estimator 20 calculates the load torque T1 corresponding to the compressor work AW1 from the compressor work AW which is the output of the first enthalpy calculator 19. FIG. 3 shows this relationship.

The voltage-frequency characteristic determination device 21 determines the optimum voltage-frequency characteristic corresponding to the load torque from the load torque T output from the load torque estimator 20. FIG. 4 shows this relationship. FIG. 4 shows a voltage-frequency characteristic using load torque as a parameter.

The waveform storage device 12 outputs the waveform pattern of the determined voltage-frequency characteristic from the output signal of the voltage-frequency characteristic determining device 21 to the waveform generating device 13, and the waveform generating device 13 generates the waveform signal. The waveform signal is output to the inverter device 14. The inverter device 14 receives the waveform signal from the waveform generator 13 and controls the compressor 1.

As described above, according to this embodiment, the compressor work load and the load torque value are estimated from the information indicating the operating condition of the air conditioner, such as the discharge pressure, discharge temperature, suction pressure, and suction temperature of the compressor. By operating with the optimum voltage-frequency characteristics according to the load torque, it is possible to operate the air conditioner with high efficiency.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 shows the second aspect of the present invention.
FIG. 6 is a schematic configuration diagram of the air conditioner in the embodiment, and FIG. 6 is a Mollier diagram of the air conditioner in the embodiment.

In FIG. 5, the shell discharge temperature detector 16
And shell suction pressure detector 17 and shell suction temperature detector 1
Reference numeral 8 is connected to the second enthalpy calculator 22, which calculates the work of the compressor 1 from the output information of each detector, and calculates the work AW of the compressor as the load torque estimator 20. Output to. The load torque estimator 20 calculates the load torque from the compressor work AW and outputs a signal corresponding to the load torque to the voltage-frequency characteristic determination device 21.

The voltage-frequency characteristic determining device 21 determines the optimum voltage-frequency characteristic corresponding to the load torque based on the load torque signal, and outputs a signal corresponding to the voltage-frequency characteristic to the waveform storage device 12.

The waveform storage device 12, which stores waveform patterns of different voltage-frequency characteristics, outputs the waveform pattern of the optimum voltage-frequency characteristic to the waveform generator 13 according to the voltage-frequency characteristic signal.

FIG. 6 is a Mollier diagram, in which the vertical axis represents pressure and the horizontal axis represents enthalpy. From the Mollier diagram of FIG. 6, the enthalpy E1 can be calculated from the shell suction pressure P2 of the compressor 1 and the shell suction temperature t2. Enthalpy E2 can be estimated.

That is, the compressor work amount AW can be estimated from the relationship of AW1 = E2-E1. The load torque estimator 20 outputs the work of the compressor A which is the output of the second enthalpy calculator 21.
From W to load torque T1 corresponding to compressor work AW1
Is calculated (see FIG. 3).

The voltage-frequency characteristic determining device 21 determines the optimum voltage-frequency characteristic corresponding to the load torque from the load torque T which is the output of the load torque estimator 20 (FIG. 4).
reference).

The waveform storage device 12 outputs the waveform pattern of the determined voltage-frequency characteristic from the output signal of the voltage-frequency characteristic determining device 21 to the waveform generating device 13, and the waveform generating device 13 generates the waveform signal. The waveform signal is output to the inverter device 14. The inverter device 14 receives the waveform signal from the waveform generator 13 and controls the compressor 1.

As described above, according to the present embodiment, the work load of the compressor and the load torque value are estimated from the information indicating the operating temperature of the air conditioner such as the discharge temperature, the suction pressure, and the suction temperature of the compressor, and the load torque is calculated. Thus, the air conditioner can be efficiently operated by operating with the optimum voltage-frequency characteristic.

However, in the case of this embodiment, the accuracy is lower than that of the first embodiment by the fact that there is no discharge pressure information, but in terms of cost, the discharge side pressure detector is not required, so the cost reduction effect is obtained. Is obtained.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 7 shows the third aspect of the present invention.
FIG. 8 is a schematic configuration diagram of the air conditioner in this embodiment, and FIG. 8 is a Mollier diagram of the air conditioner in the embodiment.

In FIG. 7, the shell discharge pressure detector 15
And shell discharge temperature detector 16 and shell suction temperature detector 1
8 is connected to the third enthalpy calculator 23, which estimates the work of the compressor 1 from the output information of each detector, and the compressor work AW is used as the load torque estimator 20. Output to.

The load torque estimator 20 determines the compressor work amount AW.
Then, the load torque T1 is calculated, and a signal corresponding to the load torque is output to the voltage-frequency characteristic determination device 21.

The voltage-frequency characteristic determining device 21 determines the optimum voltage-frequency characteristic corresponding to the load torque based on the load torque signal, and outputs a signal corresponding to the voltage-frequency characteristic to the waveform storage device 12.

The waveform storage device 12, which stores waveform patterns of different voltage-frequency characteristics, outputs the waveform pattern of the optimum voltage-frequency characteristic to the waveform generator 13 according to the voltage-frequency characteristic signal. FIG. 8 is a Mollier diagram, in which the vertical axis represents pressure and the horizontal axis represents enthalpy.

The enthalpy E2 can be calculated from the shell discharge pressure P1 of the compressor 1 and the shell discharge temperature t1 from the Mollier diagram of FIG. By doing so, the enthalpy E1 can be estimated.

That is, the compressor work amount AW can be estimated from the relationship of AW1 = E1-E2. The load torque estimator 20 outputs the work of the compressor A which is the output of the third enthalpy calculator 23.
The load torque T1 corresponding to the work of the compressor is calculated from W (see FIG. 3).

The voltage-frequency characteristic determination device 21 is connected to the waveform storage device 12. The voltage-frequency characteristic determination device 21 outputs the load torque T which is the output of the load torque estimator 20.
From this, the optimum voltage-frequency characteristic corresponding to the load torque is determined (see FIG. 4).

The waveform storage device 12 outputs the waveform pattern of the determined voltage-frequency characteristic from the output signal of the voltage-frequency characteristic determining device 21 to the waveform generating device 13, and the waveform generating device 13 generates the waveform signal. The waveform signal is output to the inverter device 14. The inverter device 14 receives the waveform signal from the waveform generator 13 and controls the compressor 1.

As described above, according to the present embodiment, the compressor work load and the load torque value are estimated from the information indicating the operating condition of the air conditioner, such as the discharge pressure, discharge temperature and suction temperature of the compressor, and the load torque is calculated. As a result, the air conditioner can be operated efficiently by operating with the optimum voltage-frequency characteristics.

The sensor generally used for measuring the suction pressure is
Higher in accuracy than the sensor used to measure the discharge pressure,
Since it is expensive in terms of cost, if the discharge side pressure detector is used instead of the suction side pressure detector, the accuracy will be lower than in the case of using the suction side pressure detector, but in terms of cost. Since the suction side pressure detector is not required, a further large cost reduction effect can be obtained.

[0053]

As described above, the present invention provides a compressor whose rotation speed is controlled by an inverter device, a shell discharge pressure detector for detecting the shell discharge pressure of the compressor, and a shell discharge for detecting the shell discharge temperature. Temperature detector, shell suction pressure detector for detecting shell suction pressure, shell suction temperature detector for detecting shell suction temperature, shell discharge pressure detector, shell discharge temperature detector, shell suction pressure detector, shell A first enthalpy computing unit that computes the work of the compressor from the output signal of the intake temperature detector; a load torque estimator that estimates the load torque of the compressor from the output of the first enthalpy computing unit; A voltage-frequency characteristic determining device for determining the optimum voltage-frequency characteristic from the output, and a waveform pattern of different voltage-frequency characteristics are stored and the voltage-frequency characteristic is stored. A waveform storage device that outputs a waveform pattern of an optimum voltage-frequency characteristic by the output of the characteristic determination device, and a waveform generation device that generates a waveform from the waveform pattern output by the waveform storage device and outputs the waveform to the inverter device. Therefore, the compressor work load and load torque value are estimated from the information indicating the operating condition of the air conditioner, such as the discharge pressure, discharge temperature, suction pressure, and suction temperature of the compressor,
By operating with an optimum voltage-frequency characteristic according to the load torque value, it is possible to operate the air conditioner with high efficiency.

Further, the compressor whose rotation speed is controlled by the inverter device, the shell discharge temperature detector for detecting the shell discharge temperature of the compressor, the shell suction pressure detector for detecting the shell suction pressure, and the shell suction temperature are Of the shell suction temperature detector, the shell discharge temperature detector, the shell suction pressure detector, and the output signal of the shell suction temperature detector, which calculate the work of the compressor, and the second enthalpy calculator. A load torque estimator that estimates the load torque of the compressor from the output, a voltage-frequency characteristic determination device that determines the optimum voltage-frequency characteristic from the output of the load torque estimator, and waveforms of different voltage-frequency characteristics A waveform storage device that stores a pattern and outputs a waveform pattern of an optimum voltage-frequency characteristic by the output of the voltage-frequency characteristic determination device; Information indicating the operating state of the air conditioner, such as the discharge temperature, the suction pressure, and the suction temperature of the compressor, which is composed of a waveform generator that generates a waveform from the waveform pattern output by the storage device and outputs the waveform to the inverter device. Efficient operation of the air conditioner can be achieved by estimating the compressor work load and load torque value and operating with the optimum voltage-frequency characteristics according to the load torque value.

However, in this case, although there is no discharge pressure information in terms of accuracy, the cost is reduced because the discharge side pressure detector is not required in terms of cost.

Further, a compressor whose rotation speed is controlled by an inverter device, a shell discharge pressure detector for detecting the shell discharge pressure of the compressor, a shell discharge temperature detector for detecting the shell discharge temperature, and a shell suction temperature are shown. Of the shell suction temperature detector for detecting, the shell discharge pressure detector, the shell discharge temperature detector, and the output signal of the shell suction temperature detector, the third enthalpy calculator for calculating the work of the compressor, and the third enthalpy calculator A load torque estimator that estimates the load torque of the compressor from the output, a voltage-frequency characteristic determination device that determines the optimum voltage-frequency characteristic from the output of the load torque estimator, and waveforms of different voltage-frequency characteristics A waveform storage device that stores a pattern and outputs a waveform pattern of an optimum voltage-frequency characteristic by the output of the voltage-frequency characteristic determination device; Information that indicates the operating condition of the air conditioner, such as the discharge pressure, discharge temperature, and suction temperature of the compressor, as it is composed of a waveform generator that generates a waveform from the waveform pattern output by the storage device and outputs it to the inverter device. Efficient operation of the air conditioner can be achieved by estimating the compressor work load and load torque value and operating with the optimum voltage-frequency characteristics according to the load torque value.

The sensor generally used for measuring the suction pressure is
Higher in accuracy than the sensor used to measure the discharge pressure,
Since it is expensive in terms of cost, if the discharge side pressure detector is used instead of the suction side pressure detector, the accuracy will be lower than in the case of using the suction side pressure detector, but in terms of cost. Since the suction side pressure detector is not required, a further large cost reduction effect can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an air conditioner according to a first embodiment of the present invention.

FIG. 2 is a Mollier diagram of the air conditioner according to the first embodiment of the present invention.

FIG. 3 is a characteristic diagram showing the relationship between compressor work load and load torque in the first to third embodiments of the present invention.

FIG. 4 is a characteristic diagram showing a relationship between load torque and voltage-frequency characteristics in the first to third embodiments of the present invention.

FIG. 5 is a schematic configuration diagram of an air conditioner according to a second embodiment of the present invention.

FIG. 6 is a Mollier diagram of the air conditioner according to the second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of an air conditioner according to a third embodiment of the present invention.

FIG. 8 is a Mollier diagram of the air conditioner according to the third embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of an air conditioner in a conventional example.

FIG. 10 is an operation flowchart of the waveform generator in the air conditioner of the conventional example.

FIG. 11 is a characteristic diagram showing the relationship between the suction pressure and the voltage-frequency characteristic in the air conditioning apparatus of the conventional example.

[Explanation of symbols]

 1 Compressor 12 Waveform Storage Device 13 Waveform Generator 14 Inverter Device 15 Shell Discharge Pressure Detector 16 Shell Discharge Temperature Detector 17 Shell Suction Pressure Detector 18 Shell Suction Temperature Detector 19 First Enthalpy Calculator 20 Load Torque Estimator 21 Voltage-frequency characteristic determination device 22 Second enthalpy calculator 23 Third enthalpy calculator

Claims (3)

[Claims] 1. A compressor whose rotation speed is controlled by an inverter device, a shell discharge pressure detector for detecting a shell discharge pressure of the compressor, a shell discharge temperature detector for detecting a shell discharge temperature, and a shell suction pressure. A shell suction pressure detector, a shell suction temperature detector for detecting a shell suction temperature, the shell discharge pressure detector, the shell discharge temperature detector, the shell suction pressure detector, and the shell suction temperature detector A first enthalpy computing unit that computes the work of the compressor from the output signal of, a load torque estimator that computes the load torque of the compressor from the output of the first enthalpy computing unit, and an output of the load torque estimator A voltage-frequency characteristic determining device for determining an optimum voltage-frequency characteristic, and a waveform pattern of each different voltage-frequency characteristic is stored to store the voltage-frequency characteristic. A waveform storage device that outputs a waveform pattern of an optimum voltage-frequency characteristic by the output of the characteristic determination device, and a waveform generation device that generates a waveform from the waveform pattern output by the waveform storage device and outputs the waveform to the inverter device. Air conditioner. 2. A compressor whose rotation speed is controlled by an inverter device, a shell discharge temperature detector for detecting a shell discharge temperature of the compressor, a shell suction pressure detector for detecting a shell suction pressure, and a shell suction temperature. A shell suction temperature detector, a second enthalpy calculator that calculates a compressor work amount from output signals of the shell discharge temperature detector, the shell suction pressure detector, and the shell suction temperature detector; 2. A load torque estimator that estimates the load torque of the compressor from the output of the enthalpy calculator, and a voltage-frequency characteristic determination device that determines the optimum voltage-frequency characteristic from the output of the first load torque calculator. Waveform patterns having different voltage-frequency characteristics are stored, and an optimum voltage-frequency characteristic waveform pattern is output by the output of the voltage-frequency characteristic determining device. An air conditioner comprising: a waveform storage device; and a waveform generator that generates a waveform from the waveform pattern output by the waveform storage device and outputs the waveform to the inverter device. 3. A compressor whose rotation speed is controlled by an inverter device, a shell discharge pressure detector for detecting a shell discharge pressure of the compressor, a shell discharge temperature detector for detecting a shell discharge temperature, and a shell suction temperature. A shell suction temperature detector, a third discharge pressure detector, a third discharge temperature detector, and a third enthalpy calculator for calculating a compressor work amount from output signals of the shell suction temperature detector; The load torque estimator that estimates the load torque of the compressor from the output of the 3 enthalpy calculator and the voltage-frequency characteristic determination device that determines the optimum voltage-frequency characteristic from the output of the load torque estimator are different from each other. A waveform for storing the waveform pattern of the voltage-frequency characteristic and outputting the waveform pattern of the optimum voltage-frequency characteristic by the output of the voltage-frequency characteristic determining device. An air conditioner comprising a storage device and a waveform generator that generates a waveform from the waveform pattern output by the waveform storage device and outputs the waveform to the inverter device.