JPH11206188A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inverter device that can grasp electric power, integrating electric energy, electricity charge, or the like. SOLUTION: An inverter device 12 for changing the operation frequency of a three-phase AC electric motor 11 and the rotary speed of an electric motor is provided with a means 13 for detecting electric power being supplied to the electric motor 11 and a means 15 for displaying the detected power. Also, the inverter device 12 has a means for integrating the detected power and it is preferable that the integrated electric energy can be displayed. Furthermore, it is preferable that the inverter device 12 is provided with a means for setting electricity charge per unit electric energy and a means for multiplying the integrated electric energy by the electricity charge per unit electric energy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device suitable for energy-saving operation of a motor by changing the rotation speed of the motor by changing a power supply frequency of a three-phase AC motor or the like.

[0002]

2. Description of the Related Art Conventionally, there has been known an inverter device that changes a rotation speed of a three-phase AC motor by changing an operation frequency of the motor. The inverter device is applied to various devices using a three-phase AC motor, and is used for, for example, a pump for pumping water. Generally, at the installation site of the pump device, the capacity is selected according to the assumed maximum load, so that an excessive pump capacity is often installed, and the pump is operated with the excess pump capacity during normal operation. Often.

[0003] In these cases, in many cases, the amount of water is adjusted by restricting the valve on the pump discharge side. However, when the amount of water is reduced by a valve, the pump is operated at the maximum rotation speed (rated rotation speed), so only the apparent pipe resistance increases, and the pump power is not much different from the case where the valve is fully opened. , Does not save energy. When an inverter device is used for such a pump device, the amount of water can be adjusted by lowering the rotation speed of the pump. In this case, the power (electric power) decreases in proportion to the cube of the rotation speed, so that the energy saving effect is remarkable.

[0004] A method is known in which an inverter device is mounted on the primary power supply side of existing pump equipment such as factory equipment and the like, and the number of revolutions is reduced to reduce electric power and save energy. Generally, in existing pump equipment, an excessive capacity pump is often installed in order to observe a change in pipe diameter and a safety factor. For this reason, there are many cases where there is no problem even if the rotation speed is reduced, and mounting an inverter device is effective for energy saving.

[0005]

A conventional inverter device generally has a function of displaying current, voltage, frequency and the like, but it is necessary to know the actual active power from the current value and voltage value. Can not. Therefore, the operation manager who manages the operation of the pump cannot realize the degree of energy saving.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an inverter device capable of ascertaining power, an integrated power amount, a power rate, and the like.

[0007]

According to the present invention, there is provided an inverter apparatus for changing the operating frequency of a three-phase AC motor to change the rotation speed of the motor. And a display means for displaying the obtained power. Thus, by changing the operating frequency of the three-phase AC motor, the power changes in proportion to the cube of the rotation speed, but the operation manager can directly grasp the reduction as an actual feeling. Therefore, the energy saving effect can be easily measured.

Further, it is preferable that the inverter device includes a means for integrating the detected power, and the integrated power amount can be displayed. Thereby, since the accumulated electric energy can be grasped, for example, the electric energy per hour or the electric energy per day can be grasped.

Further, it is preferable that the inverter device includes means for setting a power rate per unit power amount, and means for multiplying the integrated power amount by the power rate per unit power amount. Thus, by inputting a power rate per unit power amount, for example, an hourly or daily power rate of a three-phase AC motor or the like can be grasped. Therefore, the energy saving effect can be grasped more intuitively, and energy management in factories and the like becomes easier.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an inverter device according to an embodiment of the present invention. The input side of the inverter device 12 is connected to, for example, a three-phase 200 V 50 Hz or 60 Hz commercial AC power supply, and the output side thereof is connected to the three-phase AC motor 11 to supply electric power of an arbitrary AC frequency and voltage. The inverter device 12 includes a converter unit 12a that rectifies a three-phase commercial AC power supply and converts it into DC power, a smoothing capacitor 12b that stores DC power, and an inverter that reversely converts DC power into AC power of an arbitrary frequency and voltage. The main part is composed of a part 12c.

An ammeter 13a for detecting U-phase and W-phase currents and a voltmeter 13b for detecting UV-phase and VW-phase voltages are connected to the secondary power line of the inverter. , And these signal outputs are input to the power detector 13. The power detector 13 outputs a power value of active power supplied from the phase current and the inter-phase voltage to the three-phase AC motor 11 which is the load of the inverter 12. The output power value is transmitted to the CPU 14 in the inverter device 12 by A / A.
The data is input through a D converter or the like and stored in a storage device.
The inverter device 12 includes a display unit 15 such as a liquid crystal panel, for example, and displays the power value detected by the power detector 13.

FIG. 2 shows the principle of measuring the active power by the digital sampling method. From the output value of the voltmeter 13b, a sampling result of the voltage waveform is obtained as shown in FIG. Similarly, a sampling result of the current waveform is obtained from the output value of the ammeter 13a as shown in FIG.
In general, the active power is represented by the following equation as a result of integrating the instantaneous power, which is the product of the instantaneous values of the voltage and the current, and averaging over one cycle T.

[0014]

(Equation 1)

From the approximate expression on the right side of the above equation, the active power is obtained by averaging the sum (one period) of k (= T / Δt) strips of instantaneous power having a width of the sample period Δt in the period T. Is obtained by By executing the contents of such an expression almost as it is by the CPU 14, the power can be measured by the digital sampling method. In practice, the waveform measurement time is often set to be longer than one cycle in order to increase the measurement accuracy. In general, Δt is about several tens μs,
The reciprocal is the sampling frequency. Further, since the above equation is the power per phase, the power is three times in the case of three phases.

FIG. 3 shows the principle of measuring the active power by the sum averaging method. The voltage input waveform and the current input waveform which are the outputs of the ammeter 13a and the voltmeter 13b are as shown in FIG. The active power is obtained by integrating the product of the instantaneous value of the voltage and the current by the time of one cycle (or n cycles) and dividing the product by the cycle, as shown in the following equation.

[0017]

(Equation 2)

Therefore, it is necessary to accurately sample one cycle (or n cycles) of the input waveform of voltage and current. This method is realized by synchronizing the cycle of the input waveform of the voltage and current with the sampling period using a zero-cross signal based on the current input waveform as shown in FIG. 3B. The active power is determined by averaging the product of the instantaneous values of the voltage and the current during the active sampling period using the above approximate expression. The approximate expression by sampling is shown below. When the current input signal is small, the zero-cross signal of the voltage waveform is used as a reference.

[0019]

(Equation 3)

The CPU 14 integrates the sequentially stored power values at regular time intervals and calculates the integrated value per unit time, thereby obtaining the integrated power amount (kwh) per unit time.
Can be calculated. Then, by outputting this to the display device 15 and displaying it, the electric energy per unit time (k
wh) can be displayed.

The CPU 14 is connected to an input device 17 such as a numeric keypad, for example, and can set a power rate per unit power amount. As shown in FIG. 4, a multiplier 14a is provided inside the CPU 14, and can calculate the product of the power rate per unit power amount and the integrated power amount, thereby calculating the power rate. By displaying this on the display device 15, it is possible to display the power consumption fee. When there is a difference between the basic charge and the night charge, the power charge is calculated by using the clock function in the CPU 14 to separately store the integrated power amounts at night and during the day, It is possible to calculate a power rate according to the rate of the power.

In general, an inverter device often includes current detecting means and voltage detecting means. This is because it is necessary to display the actual use current or use voltage with respect to the rated current or the rated voltage, for example. Therefore, also in the above-described measurement of the active power, the current detection means and the voltage detection means existing in the inverter device can be used as they are. Similarly, the inverter device often includes a CPU. This is because, for example, control by pulse width modulation or the like is used to generate the oscillation frequency of the inverter device. Therefore, in the above-described power measurement, integrated power measurement, and power rate calculation, the existing CP
It is possible to respond by changing the program of U. As described above, the present invention can be easily and inexpensively implemented by utilizing the existing components of the inverter device.

In the above embodiment, the calculation of the active power uses the digital sampling method.
This output may be taken into the CPU using an analog wattmeter. Further, in this embodiment, an example of the energy saving operation of the pump has been described. However, it is needless to say that the present invention can be widely used for not only the pump but also various rotating machines such as a blower, an exhaust fan, a compressor and the like.

[0024]

According to the present invention as described above,
It is possible to display the power, power amount, power rate, and the like of the inverter device. This allows the operation manager who manages the operation of the pump and the like to intuitively grasp the degree of the energy saving effect by the optimal rotation speed using the inverter device. This facilitates energy-saving diagnosis of factory equipment and the like, which can contribute to energy saving of factory equipment and the like. Further, promotion of energy saving can contribute to prevention of environmental pollution such as CO ₂ .

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing an inverter device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating calculation of active power in a digital sampling method.

FIG. 3 is an explanatory diagram of calculation of active power by a sum average method.

FIG. 4 is a block diagram relating to calculation of a power rate.

[Explanation of symbols]

 Reference Signs List 11 three-phase AC motor 12 inverter device 13 power detector 14 CPU 15 display unit 17 input device

Claims (3)

[Claims] 1. An inverter device for changing the operating frequency of a three-phase AC motor to change the rotation speed of the motor, comprising: a power detecting means for supplying power to the motor; and a display means for displaying the detected power. An inverter device characterized by the above-mentioned. 2. The inverter device according to claim 1, wherein the inverter device includes a means for integrating the detected power, and is capable of displaying the integrated power amount. 3. The inverter device includes: a unit for setting a power rate per unit power amount; and a unit for multiplying the integrated power amount by a power rate per unit power amount. 3. The inverter device according to claim 2, wherein the power rate of the integrated power amount can be displayed by inputting the power rate.