WO2004102212A1

WO2004102212A1 - Electric power measuring apparatus

Info

Publication number: WO2004102212A1
Application number: PCT/JP2004/006787
Authority: WO
Inventors: Masaji Haneda
Original assignee: Ntt Data Ex Techno Corporation
Priority date: 2003-05-16
Filing date: 2004-05-13
Publication date: 2004-11-25
Also published as: JP2004347322A

Abstract

There are included a parallel circuit, which comprises a rectifying element (11) and current control means (12), for providing predetermined and approximately equal voltage drops for both the positive and negative polarities of step-down AC inputs; a timer (17) for causing the current control means (12) of the parallel circuit to control a switch, at predetermined intervals, such that a voltage drop occurs in the step-down AC inputs; a current detection part (15) for detecting a load current flowing through a load; and an electric power amount calculating part (16) for calculating, based on both the current as detected by the current detection part (15) and a voltage applied to the current detection part (15) during that current detection, the electric power consumed in the load.

Description

Technical field

The present invention relates to a power measurement device, and more particularly to a power measurement device that accurately measures and displays power consumption even with a load other than a resistive load.

Akita

Background art

Article 26 of the Electricity Business Law stipulates restrictions on the supply voltage, and Article 44 of the Enforcement Regulations of the Electricity Business Law, which is subject to this provision, sets the standard voltage range to be maintained at 101 V ± 6 V, That is, it is specified as 95 V to 107 V.

'By the way, many devices used as loads can operate sufficiently even at 100 V or less (for example, about 95 V). Therefore, in such a device, an energy saving effect can be expected by reducing the supply voltage. In particular, with the recent call for energy-saving nourishment activities to prevent global warming, the voltage of the single-phase power supply that drives electrical equipment in factory offices is reduced to a certain voltage, which is equivalent to the reduced component. Power saving devices that save power are drawing attention.

A power saving device that reduces the supply voltage to a certain voltage in a powerful situation and saves the power corresponding to the step-down component has a function to measure and calculate the input and output voltages and the power consumption by the load. However, there is a disclosure example of a power saving device that calculates and displays an energy saving power amount from the measured value by calculation (for example, see Patent Document 1).

Patent Document 1

Japanese Unexamined Patent Publication No. 2000-110640 (Page 3, FIG. 1)

In the power saving device disclosed in Patent Document 1, the load is actually reduced to ^^ which is a resistive load. The power consumption of the inverter is calculated and displayed. For loads other than resistive loads, for example, loads incorporating an inverter power supply (hereinafter referred to as “inverter loads”), the voltage-power characteristics measured in advance To display the power consumption.

However, in the case of an inverter load, the power consumed by the load varies greatly depending on the on / off state of the load power supply and changes in the operating state of the load. There was a problem that power consumption could not be displayed.

In particular, in recent years, the use of inverter loads has increased, and the voltage-power characteristics of these inverter loads have a complicated appearance depending on the characteristics of the inverter load itself, and the overall load including the inverter load has a complicated appearance. It is required that power consumption be accurately measured on the spot and the measurement results be displayed instantaneously.

by the way,

In view of such a situation, an object of the present invention is to provide a power measuring device that can calculate and display accurate power consumption without depending on the type of load. Disclosure of the invention

The power measuring device according to the present invention is applied to an AC voltage control device for supplying a step-down AC input stepped down to a predetermined voltage to a load, or is used in combination with the AC voltage control device, and A power measuring device for calculating the power consumption consumed in the step-down AC input; voltage drop means for generating a voltage drop substantially the same as the predetermined force for any of the positive polarity and the negative polarity of the step-down AC input; Control means for controlling the voltage drop means to perform switching control as to whether or not to cause a voltage drop in the step-down AC input; current detection means for detecting a load current flowing through the load; And a power amount calculating means for calculating the power consumption consumed by the load based on the current detected at step (a) and the voltage input to the current detecting means at the time of detecting the current.

According to the present invention, the voltage drop means has a positive polarity and a negative polarity of the step-down AC input. PT / JP2004 / 006787

Three

A predetermined and substantially the same voltage drop is generated with respect to the polarity of the shift, and the control means controls the voltage drop means to lower the voltage of the step-down AC input, and performs switching control of whether or not the voltage drops. The electric energy calculating means is consumed by the load using both the current detected by the current detecting means for detecting the load current flowing through the load and the voltage input to the current detecting means when the current is detected. The power consumption is calculated.

In the power measuring device according to the next invention, the power amount calculating means includes: a current detected by the current detecting means a predetermined time immediately after a voltage drop occurs by the voltage dropping means; Sometimes, the power consumption of the load is calculated based on the voltage input to the current detection means.

According to the present invention, the electric energy calculation means comprises: a current detected by the current detection means after a predetermined time immediately after the voltage drop by the voltage drop means; and a voltage input to the current detection means at the time of the current detection. And the power consumed by the load is calculated based on!

In the power measuring device according to the next invention, the control means periodically repeats switching control of the voltage drop means at predetermined intervals.

According to the present invention, since the control means periodically repeats the control of the voltage drop means at predetermined intervals, it is possible to increase the number of times of calculation of the power consumption and to increase the calculation accuracy. .

In the power measuring device according to the next invention, the power amount calculating means includes: a current detected by the current detecting means when the voltage dropping means does not cause a voltage drop (a first detected current); When the first detection current flows, a voltage (first detection voltage) inputted to the current detection means is detected, and these detected values are held. A current (second detection current) detected by the current detection means when the voltage is generated, and a voltage (second detection voltage) input to the current detection means when the second detection current flows. ), And holds these detected values. The difference value (detected difference current) between the held second detected current and the first detected current and the held second Holds the difference between the detection voltage and the first detection voltage (detection difference voltage) Then, based on the amount of change in power consumption due to the voltage drop component (measured reduction power) calculated using the held detection difference current and detection difference voltage, the amount of change in power consumption to be reduced (calculation reduction power) Is calculated.

According to the present invention, the electric energy calculation means performs the following processing. First, a first detection current which is a current detected by the current detection means when no voltage drop occurs in the voltage drop means, and a first detection current which is a voltage input to the current detection means in this state. The detection voltage is detected, and the first detection current and the first detection voltage are held. Next, a second detection current that is a current detected by the current detection means when a voltage drop occurs in the voltage drop means, and a second detection current that is a voltage input to the current detection means in this state. And the second detection current and the second detection voltage. Then, while holding the detection difference current which is the difference value between the second detection current and the first detection current, the detection difference voltage which is the difference value between the second detection voltage and the first detection voltage is also held. . Finally, based on the measured reduced power, which is the amount of change in power consumption due to the voltage drop component calculated using the detected differential current and detected differential voltage, the calculated reduced power, which is the amount of change in the reduced power consumption, is calculated. I try to do it.

In the power measuring apparatus according to the next invention, it is characterized in that the load includes an imperter load.

According to the present invention, it is possible to calculate the power consumption of the load even when the load includes the impeller load.

In the power measuring device according to the next invention, the step-down voltage when the voltage drop is caused by the voltage drop means and the voltage supplied to the load when the voltage drop is not caused by the voltage drop means. Is characterized in that the step-down rate, which is the ratio of the above, is approximately 0.6%.

According to the present invention, when the ratio between the step-down voltage when the voltage drop is caused by the voltage drop means and the voltage supplied to the load when the voltage drop is not caused by the voltage drop means is defined as a step-down rate, By setting this step-down rate to about 0.6%, The relationship between the state in which the output reduction power is determined and the state in which the measurement reduction power is measured can be maintained in a linear state.

The power measuring device according to the next invention is characterized in that the predetermined time immediately after the voltage drop by the voltage drop means is about several seconds.

According to the present invention, the power consumption is calculated after several seconds from the occurrence of the voltage drop after the recovery of the power consumption characteristic consumed by the inverter load. Power can be calculated.

In a power measuring device according to the next invention, a voltage drop generated by the voltage drop means is approximately 0.6 V.

According to the present invention, by setting the voltage drop generated by the voltage drop means to about 0.6 V, it is possible to maintain the relationship between the state in which the calculated reduced power is obtained and the state in which the measured reduced power is measured is maintained. And the forward voltage drop of the rectifier can be used.

In the power measuring device according to the next invention, the voltage dropping means includes: a first step of generating a forward voltage drop with respect to one of a positive polarity and a negative polarity of the step-down AC input. A rectifying element, and a parallel circuit of a second rectifying element connected in anti-parallel to the first rectifying element, wherein the control means is configured to control the first rectifying element and the second rectifying element. It is characterized in that one of the conduction / non-conduction is switched and controlled.

According to the present invention, the voltage dropping means includes a first rectifying element that causes a voltage drop with respect to one of the positive polarity and the negative polarity of the step-down AC input, and an inverse of the first rectifying element. A parallel circuit with a second rectifying element connected in parallel is provided, and the control means switches between the conduction and non-conduction of one of the first rectifying element and the second rectifying element. I control it.

In the power measuring device according to the next invention, one of the first rectifier and the second rectifier is a field-effect transistor. According to the present invention, since one of the first rectifying element and the second rectifying element is a field effect transistor, the above-described voltage drop means can be realized with a single element. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing a basic configuration of a power measuring device according to a first embodiment of the present invention. FIG. 2 is a diagram showing a relationship between time and power consumption when a step-down voltage is supplied. FIG. 3 is a graph schematically illustrating a power measurement device according to a second embodiment of the present invention. '' Best mode for carrying out the invention

Hereinafter, preferred embodiments of a power measurement device according to the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited by the embodiment.

Embodiment 1

FIG. 1 is a diagram showing a basic configuration of a power measuring device according to a first embodiment of the present invention. In the figure, an AC voltage control device 1 and a power measuring device 10 are connected in series between input terminals R 1 and N 1 as AC input terminals and output terminals R 2 and N 2 as AC output terminals. It is connected. The power measurement device 10 includes a rectifier 11, current control means 12, a timer 17, a current detection unit 15, and a power amount calculation unit 16. It should be noted that, in the figure, the configuration of the current control means 12 is shown as a ^! Lonely configuration comprising a parallel circuit of the rectification means 13 and the switching means 14.

In the power measuring device 10 shown in FIG. 1, a rectifying element 11 and a current control means 12 constitute a parallel circuit in which one end of the parallel circuit is connected to one output of the AC voltage control device 1. And the other end is connected to one end of the current detector 15. The other end of the current detector 15 constitutes one end of the output terminal of the power measuring device 10 and is connected to the output terminal R2. The other end of the output terminal of the power measurement device 10 is connected to the other output terminal of the AC voltage control device 1. It constitutes a terminal that extends the force through, and is connected to the output terminal N2. Note that the timer 17 is connected to the power supply 17 so that the on / off of the switching means 14 of the current control means 12 is controlled. In addition, using the current signal from the current detection unit 15 and the voltage signal input to the current detection unit 15, the amount of power consumed by the load connected between the output terminals R 2 and N 2 is calculated. Is connected to the electric energy calculation unit 16.

Next, the operation of the power measuring device 10 will be described. First, in FIG. 1, the AC input supplied between the input terminals R 1 and N 1 is stepped down in voltage by the AC voltage controller 1 and is supplied to the power measuring device 10. The AC input (hereinafter referred to as “step-down AC input”) supplied to the power measuring device 10 is output to the output terminal R via the parallel circuit of the rectifying element 11 and the current control means 12 and the current detecting section 15. Supplied to the load (not shown) connected between 2 and N2. The current detection unit 15 performs current detection in a form that does not affect the load current by using a current transformer or the like. The timer 17 controls switching of the ON (closed) and OFF (open) states of the switching means 14 of the current control means 12. Now, when the switching means 14 of the current control means 12 is in an ON state (hereinafter referred to as a “first state”), the step-down AC input output from the AC voltage control device 1 Switching means 1 Bypass the 4 side. At this time, no voltage drop occurs in the power measurement device 10 for any polarity of the step-down AC input (when the input terminal R1 is positive and Z is negative).

On the other hand, when the switching means 14 of the current control means 12 is in the off state (hereinafter referred to as “second state”), the voltage is supplied to the load by the polarity of the step-down AC input output from the AC voltage control device 1. The path of the AC output is different. That is, when the input terminal R 1 has a positive polarity, the current passes through the rectifier 13 of the current control means 12, and when the input terminal R 1 has a negative polarity, the current passes through the rectifier 11. At this time, if an element (for example, a voltage drop of about 0.6 V) having almost the same voltage drop characteristics in the forward direction as the rectifying element 11 and the rectifying means 13 is used, any polarity of the step-down AC input can be used. In this case, the voltage drop at the power measuring device 10 is almost the same (about 0.6 V). The electric energy calculation unit 16 calculates a current detected by the current detection unit 15 ′ in the first state (hereinafter, referred to as a “first detection current”), and inputs the current to the current detection unit 15 in that state. Detected voltage (hereinafter, referred to as “first detection voltage”), and retains these detected values.

In addition, the electric energy calculation unit 16 supplies the current detected by the current detection unit 15 in the second state (hereinafter referred to as “second detection current”) to the current detection unit 15 in that state. Detects the input voltage (hereinafter referred to as “second detection voltage”) and retains these detection values.

Further, the electric energy calculation unit 16 holds a difference value between the second detection current and the first detection current (hereinafter, referred to as a “detection difference current”), and outputs the second detection voltage and the first detection current. The difference value from the voltage (hereinafter referred to as “detection difference voltage”) is held. The detected difference current is a current component changed by the voltage drop component of the rectifier 11 or the rectifier 13, and the detected difference voltage is a voltage drop component of the rectifier 11 or the rectifier 13. This is the voltage component changed by the above.

Then, the power amount calculation unit 16 calculates the amount of change in power consumption due to the voltage drop component (hereinafter referred to as “measured power reduction”) using the detected difference current and the detected difference voltage. Then, based on the measured reduced power, the amount of change in power consumption that is reduced with respect to the difference voltage between the reference voltage and the voltage actually supplied (step-down AC input voltage as described above) This is called “calculated power reduction.”

The conditions for calculating the calculated reduced power include the state in which the actual power consumption reduction amount is to be calculated, that is, the state in which the calculated reduced power is calculated, and the state in which the actual reduction is measured, that is, the measurement reduction amount. It is assumed that the power measurement state is in a linear relationship.

Now, if the ratio of the step-down voltage of the step-down AC input to the reference voltage is defined as the step-down rate, the above-mentioned state in which the calculated reduced power is obtained is that the reference voltage is 100 V and the step-down voltage of the step-down AC Since it is V, the step-down ratio with respect to the reference voltage is (1 0 0-95) / 1 0 0 X 1 0 0 = 5%. In addition, the state where the above-mentioned measured power reduction is calculated is as follows. PC orchid 004/006787

9

Since the reference voltage is 95 V and the step-down voltage is 0.6 V, the step-down ratio with respect to the reference voltage is 0.6 / 95 X 100 = 0.63%. Within this range of the step-down rate, there is no problem even if the relationship between the two is considered to be linear.

As described above, by using the measured reduced power and the calculated reduced power obtained as described above, the power consumption at an arbitrary step-down rate within a practical range can be obtained.

The timer 17 outputs a long ON signal for turning on the switching means 14 and a short OFF signal for turning off the switching means 14, and the output of the ON / OFF signal is periodically repeated. Good. By repeating such a periodic ON / OFF signal, the number of times of calculating the power consumption can be increased, and the calculation accuracy can be improved.

The voltage stepped down by the rectifying means 13 and the rectifying element 11 of the current control means 12 is set to about 0.6 V. However, in the relationship between the step-down rate and the measurement accuracy of the reduced power described above, the step-down voltage is used. It is better to set the rate (or step-down voltage) high (for example, about IV). However, this step-down voltage cannot be set to a very high voltage (voltage higher than I V) for the following reasons. Hereinafter, the reason will be described in detail. FIG. 2 is a graph schematically showing a relationship between time and power consumption when a step-down voltage is supplied. In the figure, K1 is a curve representing the characteristic in the case of a resistive load, and K2 is a curve representing the characteristic in the case of an inverter load. In the case of a resistive load, as indicated by K1 in the figure, the power consumption before step-down is defined as P. If the reduced power consumption, which is the reduction component of power consumption, is Δ Ρ, the power consumption after step-down is P. Thus, the power consumption can be reduced. Also, this reduced power consumption Δ もない does not depend on time.

On the other hand, in the case of an inverter load, as shown by K2 in Fig. 2, immediately after the step-down AC input is supplied, the power consumption decreases one by one, but the power consumption increases as time passes. . K2 in the figure shows an example in which the power consumption after the buck and the power consumption before the buck are almost the same.However, depending on the type of impeller load, the power consumption after the buck decreases before the buck. Some increase compared to power consumption. This tendency is common in devices with built-in inverter power supplies that supply rated output, such as personal computers. When the power supply built in these devices detects a drop in voltage, it acts to increase the current supplied from the power supply so as not to hinder the operation of 4β. As a result, in some cases, the post-buck power consumption at the load is higher than the pre-buck power consumption.

In addition, Κ2 shown in FIG. 2 also shows a characteristic in which the reduced power consumption recovers during the time of Δ Δ under the inverter load. This recovery time depends on the magnitude of the step-down voltage. If the step-down voltage is large, the recovery time will also increase. As a typical example, if the step-down voltage is about 0.6 V as described above, it will recover in about several seconds. On the other hand, when a step-down voltage of about 3 to 4 V is applied, the current continues to increase for about 4 to 5 minutes, and accurate measurement of power consumption cannot be made unless these times have elapsed.

This phenomenon causes another problem. As described above, when calculating the measured power reduction, a small voltage drop is forcibly generated, and the amount of power consumption is measured using the detected differential current and the detected differential voltage generated at that time. I am trying to do it.

However, for example, even if the detected differential current and the detected differential voltage are measured while the current is increasing as described above, a correct result cannot be obtained. On the other hand, if you try to measure in a state where the current is stable, you cannot control the timing of the measurement. Also, in this case, if the time from the step-down of the supply voltage becomes longer, the power supply of another load is turned on / off or the operation status of the other load changes in the meantime. Measurement cannot be performed in a stable state.

Furthermore, when more accurate calculated power reduction is required using the measured power reduction, it is necessary to control the measurement timing and increase the number of measurements. For this purpose, it is necessary to shorten the rise time of the power consumption recovery curve shown by K2 in FIG. That is, it is necessary to reduce the step-down voltage determined by the rectifier 13 of the rectifier 11 and the rectifier 13 of the current controller 12. Also, the step-down voltage If the value is small, it is possible to prevent flickering given to lighting equipment.

On the other hand, when the step-down voltage is made extremely small, it affects the measurement accuracy of the measurement current measured by the current detection unit 15. Therefore, in order to achieve both the above-described power consumption recovery characteristic and the measurement accuracy of the current detection unit 15, it is preferable to provide a step-down voltage of about 0.6 V.

As described above, according to the power measuring device according to the present embodiment, the voltage lowering means has a predetermined and substantially the same voltage drop for both positive and negative polarities of the step-down AC input. The control means controls the voltage drop means to periodically switch the switching of whether or not to reduce the voltage of the step-down AC input at predetermined intervals, and the power amount calculation means determines the load current flowing through the load. Since the current detected by the current detecting means for detecting the current and the voltage input to the current detecting means when the current is detected are used, the power consumption of the load is calculated. Thus, accurate power consumption can be calculated irrespective of the type of load.

Here, the voltage drop means corresponds to a parallel circuit of the rectifying element 11 and the current control means 12, and the control means corresponds to the timer 17.

Further, according to this embodiment, the voltage dropping means includes a first rectifying element that causes a forward voltage drop with respect to one of the positive polarity and the negative polarity of the step-down AC input; A parallel circuit is provided with a second rectifier element connected in antiparallel with the first rectifier element, and the control means controls the conduction of one of the first rectifier element and the second rectifier element. Since “/ non-conduction” is controlled by switching, it is possible to realize a power measurement device that calculates accurate power consumption with a simple configuration regardless of the type of load.

Here, the first rectifying element corresponds to the rectifying element 11, and the second rectifying element corresponds to the current control means 12.

Further, in power measuring device 10 of the present embodiment, a display unit may be provided separately from power calculating unit 16 and power calculating unit 16 omitting the description of the display unit. In this way, the reduction effect can be instantaneously provided to the user by displaying the calculated reduction power calculated by the power amount calculation unit 16.

Further, in the power measuring device 10 of the present embodiment, the configuration is such that it is connected immediately after the AC voltage control device 1, but it may be configured to be incorporated in the AC voltage control device 1.

Embodiment 2.

FIG. 3 is a diagram illustrating a configuration of a power measuring device according to a second embodiment of the present invention. The power measuring device of this embodiment is obtained by replacing the current control means 12 of the power measuring device 10 shown in FIG. 1 with an FET 18 which is an N-channel enhancement type field effect transistor. . The other configuration is the same as that of the first embodiment shown in FIG. 1, and the same components are denoted by the same reference numerals.

In FIG. 3, the source of the FET 18 is connected to the power source of the rectifier 11 and the drain is connected to the anode of the rectifier 11 to form a parallel circuit. In this parallel circuit, one end to which the source of the FET 18 is connected is connected to one output of the AC voltage controller 1, and the other end to which the drain of the FET 18 is connected is connected to the current detector 15. Connected to one end. The timer 17 is connected to the source and gate of the FET 18.

ON / OFF of FET 18 is controlled by a control signal from timer 17. When the FET 18 is off, an anti-parallel circuit is formed by the parasitic diode of the FET 18 and the rectifier 11. Therefore, a predetermined voltage drop (about 0.6 V) occurs for any polarity of the step-down AC input supplied from the AC voltage control device 1. On the other hand, when FET 18 is on, there is no voltage drop because the conduction state is established for any polarity of the step-down AC input.

In this way, the state can be set to the same state as in the first embodiment, and the calculation and display of the power consumption in the load can be realized by the same means as in the first embodiment. The timer 17 outputs an ON signal when the FET 18 is turned on, stops the output of the ON signal when the FET 18 is turned off, and periodically repeats the output / stop of the ON signal. What should I do? By repeating such a periodic ON signal output Z stop, the number of times of calculation of the electric energy can be increased, and the calculation accuracy can be improved.

In this embodiment, the case where an N-channel enhancement type field effect transistor is used as the FET 18 has been described. However, the present invention is not limited to this. For example, a P-channel enhancement type electric field effect transistor may be used. An effect transistor may be used. In this case, the method of applying the bias by the timer 17 is only reversed, and the power consumption in the load can be calculated and displayed based on the above-described means.

For FET 18, for example, an N-channel depletion-type field-effect transistor may be used. In this case, the timer 17 outputs an off signal when the FET 18 is turned off, stops the output of the off signal when the FET 18 is turned on, and periodically outputs / stops the off signal. Should be repeated. By repeating the periodic output / stop of the OFF signal, the number of times of calculation of the electric energy can be increased, and the calculation accuracy can be improved.

As described above, according to the power measuring device of this embodiment, the anti-parallel circuit of the rectifier element and the field-effect transistor has a predetermined polarity for both positive and negative polarities of the step-down AC input. In addition, the same voltage drop is generated, and the timer controls the anti-parallel circuit to repeatedly perform switching control as to whether or not to reduce the voltage of the step-down AC input at predetermined intervals. The power consumption consumed by the load is calculated using the current detected by the current detection unit that detects the load current flowing through the load, and the voltage input to the current detection unit when the current is detected. In this way, accurate power consumption can be calculated with a simple configuration independent of the type of load. 04 006787

14

Industrial applicability

INDUSTRIAL APPLICABILITY As described above, the present invention is useful as a power measuring device applicable to a power saving device or the like for reducing power consumption, and in particular, accurate power consumption is independent of a load connected to the power saving device. Is suitable as a power measuring device capable of calculating the power.

Claims

The scope of the claims

1. Applied to an AC voltage control device that supplies a step-down AC input that has been stepped down to a predetermined voltage to a load, or used together with the AC voltage control device to calculate the power consumed by the load In the device,

Voltage drop means for generating a predetermined and substantially the same voltage drop for both positive and negative polarities of the step-down AC input;

Control means for controlling the voltage drop means to perform switching control of whether or not to cause a voltage drop in the step-down AC input;

Current detection means for detecting a load current flowing through the load,

Power calculating means for calculating the power consumption of the load based on the current detected by the current detecting means and the voltage input to the current detecting means at the time of detecting the current. A power measuring device characterized by the above-mentioned.

2. The electric energy calculation means calculates a current detected by the current detection means a predetermined time immediately after the voltage drop occurs in the voltage drop means and a voltage input to the current detection means at the time of the current detection. 2. The power measurement device according to claim 1, wherein the power consumption consumed by the load is calculated based on the power consumption.

3. The power measuring device according to claim 2, wherein said control means periodically repeats switching control of said voltage drop means at predetermined intervals.

4. The power amount calculating means is:

A current (first detection current) detected by the current detection means when no voltage drop occurs in the voltage drop means;

A voltage (first detection voltage) input to the current detection means when the first detection current flows; And hold these detected values,

A current (second detection current) detected by the current detection means when a voltage drop occurs in the voltage drop means;

A voltage (second detection voltage) input to the current detection means when the second detection current flows;

And hold these detected values,

A difference value (detection difference current) between the held second detection current and the first detection current, and

A difference value (detection difference voltage) between the held second detection voltage and the first detection voltage, and

Hold,

Based on the amount of change in power consumption due to the voltage drop component (measurement reduction power) calculated by using the held detected difference current and detected difference voltage, the amount of change in power consumption (measurement reduction) is calculated. The power measuring device according to claim 3, wherein the power measuring device calculates the reduced power.

5. The power measuring device according to claim 2, wherein the load includes an inverter load. 6. The step-down rate, which is the ratio of the step-down voltage when the voltage drop is caused by the voltage drop means and the voltage supplied to the load when the voltage drop is not caused by the voltage drop means, is approximately 0.

3.The power measuring device according to claim 2, wherein the angle is 6 ° / _0.

7. The power measuring device according to claim 6, wherein a predetermined time immediately after a voltage drop occurs in the voltage dropping unit is about several seconds.

8. The power measuring device according to claim 2, wherein a voltage drop generated by the voltage drop means is approximately 0.6 V.

9. The voltage drop means

A first rectifying element that causes a forward voltage drop with respect to either the positive polarity or the negative polarity of the step-down AC input;

A second rectifier connected in antiparallel with the first rectifier,

With a parallel circuit of

2. The power measuring device according to claim 1, wherein the control unit controls to switch between conduction and non-conduction of one of the first rectifier element and the second rectifier element. .

10. The power measuring device according to claim 1, wherein one of the first rectifying element and the second rectifying element is a field-effect transistor.