Patent Description:
Various methods are available for testing the performance of a reactor. Among these methods, a temperature increase testing method that tests a temperature increase of a reactor during use is described in Non-Patent Document <NUM>. Non-Patent Document <NUM> specifies that, as a test simulating the case where a harmonic current is superimposed onto a fundamental wave current and flows in, energization under condition (<NUM>) or (<NUM>) below is performed.

Herein, an example of the case of allowable current type I is illustrated. (<NUM>) A fifth harmonic current having a fifth harmonic content at a fundamental wave current ratio <NUM>% is superimposed onto a rated current at a rated frequency to continuously energize a reactor (hereinafter referred to as Conventional test X). (<NUM>) A reactor is continuously energized with a fundamental wave current with which a loss of the reactor is equivalent to a total loss described below (hereinafter referred to as Conventional test Y). The total loss is a sum of an actual measured loss of the reactor during energization of the rated current at the rated frequency and an actual measured loss of the reactor during energization of the fifth harmonic current at a fundamental wave current ratio <NUM>%.

Non-Patent Document <NUM>: Japanese Industrial Standards Committee "JIS High Voltage and Extra High Voltage Phase-Advancing Capacitors and Attached Apparatus--Part <NUM>: Series Reactors (JIS C <NUM>-<NUM>: <NUM>)"
Patent document <CIT> discloses an iron loss measurement method.

Conventional test X can simulate the energization state that corresponds to the actual usage conditions, but there is a problem that currents mix into a fundamental wave power supply and a harmonic power supply from each other in a testing circuit. A circuit shown in <FIG>, for example, may be adopted as a circuit configuration for avoiding current mixing. However, there is a problem that a test performed using the circuit shown in <FIG> becomes large in scale.

Conventional test Y supplies the total loss only with the fundamental wave current without reflecting frequency dependency of a copper loss and an iron loss included in the loss of the reactor. Thus, there is a problem that the copper loss and the iron loss in the state in which the fundamental wave and the harmonic are superimposed are not accurately simulated.

An aspect of the present invention aims to realize a temperature increase test for a reactor that corresponds to the actual usage conditions with a simple testing circuit.

To solve the above problems, a temperature increase testing method for a reactor according to an aspect of the present invention includes: a step of calculating a target copper loss based on a copper loss during energization of a fundamental wave current at a predetermined current value and respective copper losses during energization of respective harmonic currents of predetermined orders at predetermined current values; a step of calculating a target iron loss based on an iron loss during energization of the fundamental wave current and iron losses during energization of the respective harmonic currents; a step of calculating a frequency and a current value of a current that creates the target copper loss and the target iron loss, respectively as a test frequency and a test current value; and a step of energizing the reactor with a test current having the test frequency and the test current value, until a temperature of a predetermined part of the reactor becomes constant.

According to an aspect of the present invention, it is possible to realize a temperature increase test for a reactor that corresponds to the actual usage conditions with a simple testing circuit.

Hereinafter, Embodiment <NUM> of the present invention will be described in detail. A series reactor for a phase-advancing capacitor or a so-called filter reactor is used in combination with a capacitor. Thus, when the capacitor and the reactor are used in combination, a harmonic current flows through the reactor in addition to a fundamental wave current.

A temperature increase testing method according to the present invention is a temperature increase testing method for a reactor capable of simulating a temperature increase in a state in which a harmonic current is superimposed onto a fundamental wave current as described above. Further, there are various types of reactors, such as an air-core type, a magnetic shielding air-core type, and a gapped iron core type. The temperature increase testing method according to the present invention targets a reactor (magnetic shielding air-core type, gapped iron core type) mainly composed of a winding and an iron core using electromagnetic steel plates.

<FIG> is a circuit diagram showing a testing circuit <NUM> of the temperature increase testing method according to Embodiment <NUM> of the present invention. As shown in <FIG>, the testing circuit <NUM> includes a frequency-variable power supply E1, a compensation capacitor C1, and a test reactor L1. The testing circuit <NUM> is a circuit that performs a temperature increase test of the test reactor L1.

A frequency and a current value of the frequency-variable power supply E1 are variable. The frequency-variable power supply E1 energizes the test reactor L1 with a test current having a test frequency fex and a test current value lex (to be described later). The compensation capacitor C1 reduces the power capacity of the frequency-variable power supply E1 for energizing the test reactor L1 with the required current.

A flow of the temperature increase testing method according to Embodiment <NUM> will be described below with reference to <FIG> and <FIG> is a diagram showing a comparison between examples of each loss during energization in temperature increase tests according to Conventional test X, Conventional test Y, Embodiment <NUM>, and Embodiment <NUM>.

With the frequency-variable power supply E1, the test reactor L1 is energized with a fundamental wave current at a predetermined first current value i21, and a loss (total loss WT21) of the test reactor L1 during energization of the fundamental wave current is measured (step S1). The first current value i21 is, for example, a rated current value of the test reactor L1.

Further, the test reactor L1 is energized with a harmonic current at a second current value i22, and a loss (total loss WT22) during energization of the harmonic current is measured (step S2). The harmonic current may be, for example, a fifth harmonic of the fundamental wave, and may have a current value at a fundamental wave current ratio <NUM>%.

Next, based on a copper loss Wcu21 during energization of the fundamental wave current at the first current value i21 and a copper loss Wcu22 during energization of the harmonic current at a predetermined second current value i22, a target copper loss Wcut is calculated (step S3). More specifically, the target copper loss Wcut is obtained as a sum of the copper loss Wcu21 during energization of the fundamental wave current and the copper loss Wcu22 during energization of the harmonic current.

The copper loss Wcu21 during energization of the fundamental wave current and the copper loss Wcu22 during energization of the harmonic current are obtained in advance by calculation. Specifically, they may be obtained using Formula (<NUM>) below. <NUM>] <MAT>.

In Formula (<NUM>), Wcu represents a copper loss, Rdc represents a direct current resistance of the winding, Re represents an alternating current resistance coefficient corresponding to an eddy current loss of the winding, f represents a frequency, and I represents a current value. The direct current resistance Rdc is an actual measured value of the test reactor L1, and the alternating current resistance coefficient Re may be obtained by simulation using a finite element method.

Next, based on an iron loss Wfe21 during energization of the fundamental wave current and an iron loss Wfe22 during energization of the harmonic current, a target iron loss Wfet is calculated (step S4). More specifically, in Embodiment <NUM>, the target iron loss Wfet is obtained as a sum of the iron loss Wfe21 during energization of the fundamental wave current and the iron loss Wfe22 during energization of the harmonic current.

Herein, the iron loss Wfe21 during energization of the fundamental wave current is obtained by subtracting the copper loss Wcu21 during energization of the fundamental wave current from the total loss WT21 during energization of the fundamental wave current. The iron loss Wfe22 during energization of the harmonic current is obtained by subtracting the copper loss Wcu22 during energization of the harmonic current from the total loss WT22 during energization of the harmonic current.

In Embodiment <NUM>, as described above, each measured total loss is separated into the iron loss and the copper loss by calculation. Specifically, the measured total loss WT21 is separated into the copper loss Wcu21 and the iron loss Wfe21, and the measured total loss WT22 is separated into the copper loss Wcu22 and the iron loss Wfe22. In the case where the target of the temperature increase test is a transformer, since there are two sets of windings, the loss at the time when the other winding is opened and there is no load may be taken as the iron loss, and the loss at the time when the other winding is short-circuited may be taken as the copper loss. However, in the case of a reactor, since there is only one set of winding, it is not possible to individually measure the iron loss and the copper loss. Thus, it is required to separate the iron loss and the copper loss by calculation as described above.

Next, a frequency and a current value of a current that creates the target copper loss Wcut and the target iron loss Wfet are respectively calculated as a test frequency fex and a test current value Iex (step S5). The test frequency fex and the test current value Iex may be calculated according to simultaneous equations of Formula (<NUM>) below. <NUM>] <MAT>.

In Formula (<NUM>), Rdc is a direct current resistance of the winding, Re is an alternating current resistance coefficient corresponding to an eddy current loss of the winding, and as described above, these values are known. Wfe is an iron loss. n is a Steinmetz's constant (approximately <NUM>) and is determined by the material constituting the test reactor L1. Kh is a hysteresis loss coefficient, and Ke is an eddy current loss coefficient, which are coefficients obtained based on the iron loss Wfe21 during energization of the fundamental wave current and the iron loss Wfe22 during energization of the harmonic current. Thus, the unknowns in Formula (<NUM>) are the frequency and the current, which are obtained by solving these simultaneous equations respectively as the test frequency fex and the test current value lex.

In the example of Embodiment <NUM> shown in <FIG>, the test frequency fex serving as a solution to the simultaneous equations takes a value between a fundamental wave frequency <NUM> and a fifth harmonic frequency <NUM> and is calculated to be approximately <NUM>, for example.

Next, the test reactor L1 is energized with a test current having the test frequency fex and the test current value lex, and the energization is performed until the temperature of a predetermined part of the test reactor L1 becomes constant (step S6). The temperature of the predetermined part is, for example, the temperature of the winding of the test reactor L1. Also, it may be the temperature of the iron core. Furthermore, in the case where the test reactor L1 is an oil-filled reactor, the temperature of the predetermined part may be the temperature of the insulating oil. In this manner, the temperature increase test according to Embodiment <NUM> is performed.

The above description pertains to the case where one harmonic current is superimposed onto the fundamental wave current. In contrast, calculation of the target copper loss Wcut and the target iron loss Wfet in the case where one or more harmonic currents are superimposed onto the fundamental wave current is as follows.

In step S3, the calculation of the target copper loss Wcut is performed based on the copper loss Wcu21 during energization of the fundamental wave current at the predetermined first current value i21, and copper losses Wcu22m. The copper losses Wcu22m are respective copper losses during energization of respective harmonic currents of predetermined orders at predetermined second current values i22m. Herein, m represents the order of the selected harmonic current. The copper loss Wcu22m represents each copper loss during energization of a harmonic current having the selected order. Thus, a copper loss Wcu22m is present for each selected order.

For example, a case where the harmonic current superimposed onto the fundamental wave current is a fifth harmonic and a seventh harmonic will be described. In this case, the target copper loss Wcut is calculated based on the copper loss Wcu21 during energization of the fundamental wave current at the predetermined first current value i21, a copper loss Wcu225 during energization of a fifth harmonic current at a predetermined second current value i225, and a copper loss Wcu227 during energization of a seventh harmonic current at a predetermined second current value i227. Specifically, the target copper loss Wcut is obtained as a sum of the copper loss Wcu21 during energization of the fundamental wave current and the copper losses Wcu22m during energization of the respective harmonic currents of the predetermined orders. In the above example, the target copper loss Wcut is obtained based on a sum of the copper loss Wcu21, the copper loss Wcu225, and the copper loss Wcu227.

Further, in step S4, the target iron loss Wfet is obtained based on the iron loss Wfe21 during energization of the fundamental wave current at the predetermined first current value i21, and iron losses Wfe22m during energization of respective harmonic currents of predetermined orders.

For example, a case where the harmonic current superimposed onto the fundamental wave current is a fifth harmonic and a seventh harmonic will be described. In this case, the target iron loss Wfet is calculated based on the iron loss Wfe21 during energization of the fundamental wave current at the predetermined first current value i21, an iron loss Wfe225 during energization of a fifth harmonic current at a predetermined second current value i225, and an iron loss Wfe227 during energization of a seventh harmonic current at a predetermined second current value i227. In other words, the target iron loss Wfet is obtained as a sum of the iron loss Wfe21 during energization of the fundamental wave current and the iron losses Wfe22m during energization of the respective harmonic currents of the predetermined orders. In the above example, the target iron loss Wfet is obtained based on a sum of the iron loss Wfe21, the iron loss Wfc225, and the iron loss Wfe227.

Herein, the iron losses Wfe22m during energization of the respective harmonic currents of the predetermined orders are obtained by subtracting the copper losses Wcu22m during energization of the respective harmonic currents of the predetermined orders from total losses WT22m during energization of the respective harmonic currents of the predetermined orders. Specifically, the iron loss Wfe225 is obtained by subtracting the copper loss Wcu225 from a total loss WT225 during energization of the fifth harmonic current. Similarly, the iron loss Wfe227 is obtained by subtracting the copper loss Wcu227 from a total loss WT227 during energization of the seventh harmonic current. In step S2, the total loss WT225 and the total loss WT227 are obtained by energizing the test reactor L1 respectively with harmonic currents of the predetermined orders (fifth harmonic current and seventh harmonic current) at predetermined current values, and measuring the losses during energization of the respective harmonic currents of the predetermined orders.

In this manner, in the case of simulating superimposition of one or more harmonic currents onto the fundamental wave current, calculations are performed based on the copper loss, the iron loss, and the total loss for each harmonic current having any selected order, and the copper loss, the iron loss, and the total loss during energization of the fundamental wave current.

The temperature increase testing method according to Embodiment <NUM> is verified below based on <FIG>. In <FIG>, the rated frequency of the fundamental wave current is <NUM>. Conventional test X is performed by superimposing a fifth harmonic current having a fifth harmonic content at a fundamental wave ratio <NUM>% onto a fundamental wave current <NUM>% to energize the test reactor, and supplying a total loss WTx.

In the column of Conventional test X in <FIG>, the copper loss Wcux calculated according to the above calculation method, and the iron loss Wfex obtained as a difference between the total loss WTx and the copper loss Wcux are shown together. Conventional test X is a test that is performed by actually energizing the test reactor L1 with a current in which a harmonic is superimposed onto the fundamental wave current to simulate the actual usage conditions.

The ratios of the copper loss Wcux and the iron loss Wfex to the total loss WTx in Conventional test X can be said to simulate the actual usage conditions. In other words, as the value of each loss in each temperature increase test approaches the value of Conventional test X, it can be said that the energization to the test reactor L1 with the test current has more faithfully simulated the actual usage conditions.

However, in Conventional test X, it is required to superimpose a harmonic onto the fundamental wave to supply to the test reactor, and there is a problem that a current flows into a fundamental wave power supply and a harmonic power supply respectively from each other. In the case of using a commercial power supply as the fundamental wave power supply, there is a problem that a harmonic current flows out to the system of the commercial power supply. Further, to secure the test current flowing into the test reactor even if the harmonic current flows out to the commercial power supply system, it is required to increase the power capacity of the harmonic power supply.

Thus, to prevent mutual current inflow between the fundamental wave power supply and the harmonic power supply, a circuit configuration for testing shown in <FIG> is known. In this circuit configuration, since two superimposition transformers (superimposition transformers Tx1 and Tx2) and two test reactors (test reactors Lx1 and Lx2) are required, the testing equipment becomes large in scale. In particular, since two test reactors with the same configuration are required, there is a problem that Conventional test X cannot be performed in the case where only one test reactor can be economically prepared.

Next, Conventional test Y is verified. As described above, Conventional test Y performs energization only with the fundamental wave current without reflecting the frequency dependency of the copper loss and the iron loss included in the loss of the reactor. Specifically, the test reactor L1 is energized with a fundamental wave current at a predetermined first current value i21, and a total loss WT21 during energization of the fundamental wave current is obtained. Further, the test reactor L1 is energized with a harmonic current at a second current value i22, and a total loss WT22 during energization of the harmonic current is obtained. Up to this point, the flow is the same as that of the temperature increase testing method according to Embodiment <NUM>.

Subsequently, in Conventional test Y, a target total loss WTy is obtained by adding the total loss WT21 during energization of the fundamental wave current and the total loss WT22 during energization of the harmonic current, and the test reactor L1 is energized with only the fundamental wave current such that the loss of the test reactor L1 becomes the target total loss WTy.

However, as is clear from Formula (<NUM>) above, the frequency characteristics are different between the copper loss and the iron loss. Thus, in Conventional test Y, it is not possible to sufficiently simulate the actual usage conditions in which two or more currents of different frequencies are superimposed. More specifically, in Conventional test Y, the copper loss Wcuy becomes a larger loss compared to the actual usage, and the iron loss Wfey becomes a smaller loss compared to the actual usage.

In <FIG>, in contrast to Conventional test X in which the copper loss Wcux is 882W and the iron loss Wfex is 990W, Conventional test Y is significantly different with the copper loss Wcuy being 1150W and the iron loss Wfey being 618W. The copper loss is approximately <NUM> times (<NUM>/<NUM>) of Conventional test X, and the iron loss is approximately <NUM> times (<NUM>/<NUM>) of Conventional test X. It is understood that Conventional test Y cannot sufficiently simulate the actual usage conditions of the reactor.

Thus, to pass the temperature increase test in Conventional test Y, it is inevitable to adopt an excessive design for the winding of the reactor, such as excessively reducing a winding resistance. Further, regarding the iron loss, since a loss of the actual usage conditions cannot be supplied during the temperature increase test, there is a problem that the verification relating to the iron core of the reactor is insufficient even if the temperature increase test is passed.

Next, the temperature increase testing method according to Embodiment <NUM> is verified. In Conventional test Y, energization has been performed with a fundamental wave current such that the loss of the test reactor L1 becomes the target total loss WTy. In other words, in Conventional test Y, regarding the test current, the frequency has been fixed at the same as the fundamental wave, and only the current value has been adjusted. In contrast, in the temperature increase testing method according to Embodiment <NUM>, by adjusting not only the current value but also the frequency of the test current, it is possible to supply a loss that corresponds to the actual usage conditions.

As shown in <FIG>, the target copper loss Wcut of Embodiment <NUM> is consistent with the value of the copper loss Wcux in Conventional test X. The target total loss WTt is the same as the target total loss WTy in Conventional test Y. It can be said that the temperature increase testing method of Embodiment <NUM> can more faithfully simulate the actual usage conditions compared to Conventional test Y.

The effects of the temperature increase testing method according to Embodiment <NUM> are as follows. The temperature increase testing method according to Embodiment <NUM> can perform energization simulating the actual usage conditions without superimposing currents of different frequencies. Further, using a fundamental wave power supply and a harmonic power supply in the testing circuit, there is no problem of current inflow from each other, and it becomes possible to realize a temperature increase test with a simple circuit configuration for testing. In addition, there is also an advantage that one test reactor would be sufficient.

Embodiment <NUM> of the present invention will be described below. Embodiment <NUM> is different from Embodiment <NUM> in that the target iron loss Wfet is corrected to obtain a corrected target iron loss Wfetl (target iron loss), and the other configurations and procedures are the same as those in Embodiment <NUM>.

Comparing the value of each loss in Embodiment <NUM> and Conventional test X in <FIG>, the target iron loss Wfet of Embodiment <NUM> is smaller than the iron loss Wfex of Conventional test X. This is because the electromagnetic steel plate constituting the iron core has nonlinear characteristics, and an iron loss in the case of superimposition (iron loss Wfex of 990W of Conventional test X in <FIG>) increases compared to a loss (target iron loss Wfet of 886W of Embodiment <NUM> in <FIG>) obtained by adding together the iron loss during energization of the fundamental wave current and the iron loss during energization of the fifth harmonic current.

<FIG> is a diagram showing examples of a hysteresis curve at <NUM> and <NUM> of a distorted wave magnetic flux including a third harmonic. As shown in <FIG>, it is clear that the shapes of hysteresis curves <NUM>, <NUM>, and <NUM> change depending on a superimposition phase θ of the harmonic. Thus, the magnitude of the iron loss in the case of superimposing the harmonic onto the fundamental wave current varies depending on the superimposition phase of the harmonic.

In this manner, the behavior of the iron loss when superimposing the harmonic current onto the fundamental wave current is complex. However, it is possible to empirically estimate the iron loss according to superimposition test results for reactors with similar designs and the material properties of the test reactor L1. The estimation can be performed more appropriately by setting a correction coefficient of the iron loss as K and setting the corrected target iron loss Wfet1 to be supplied as a value obtained by multiplying the target iron loss Wfet in Embodiment <NUM> by the correction coefficient K. The correction coefficient K is a coefficient of <NUM> or more.

In other words, the corrected target iron loss Wfet1 is obtained by multiplying the target iron loss Wfet, which is the sum of the iron loss Wfe21 during energization of the fundamental wave current and the iron loss Wfe22 during energization of the harmonic current, by a specific coefficient K. The correction coefficient K is not constant but varies depending on the magnetic flux density of the fundamental wave, the magnetic flux density of the harmonic, the superimposition phase, the material properties, etc. in the reactor.

Thus, by creating a database of the values of the correction coefficient K for reactors of various designs, it becomes possible to determine the correction coefficient K for the test reactor L1 according to the database. By determining the correction coefficient K based on the database with reference to the design conditions of the test reactor L1, it becomes possible to obtain the test current value and the test frequency that more accurately simulate the actual usage conditions.

In the example of <FIG>, K = <NUM>, and the corrected target iron loss Wfet1 after correction may be obtained as follows: corrected target iron loss Wfet1 = <NUM> × <NUM> ≈ <NUM> (W). In this manner, it becomes possible to match with the iron loss of Conventional test X in <FIG>.

Next, in the same manner as step S5 in Embodiment <NUM>, a frequency and a current value of a current that creates the target copper loss Wcut and the corrected target iron loss Wfet1 are calculated respectively as a test frequency fex1 and a test current value Iex1 according to the simultaneous equations of Formula (<NUM>).

In this manner, by obtaining the corrected target iron loss Wfet1, it is possible to realize supply of each loss that is substantially equivalent to the superimposition test of Conventional test X. As a result, a highly reliable testing method that takes into account the nonlinear characteristics of the iron core can be provided.

In addition, in the case of simulating superimposition of one or more harmonic currents on the fundamental wave current, the target iron loss Wfet is obtained by multiplying the sum of the iron loss Wfe21 during energization of the fundamental wave current and the iron losses Wfe22m during energization of the respective harmonic currents of the predetermined orders by a coefficient of <NUM> or more.

The specific examples of Embodiment <NUM> and Embodiment <NUM> above have been described based on the conditions of allowable current type I of a series reactor for a phase-advancing capacitor described in Non-Patent Document <NUM>. The present invention may also be applied to the conditions of allowable current type II. In that case, the harmonic current is a fifth harmonic of the fundamental wave and has a current value at a fundamental wave current ratio <NUM>%. Further, the present invention may also be applied to a filter reactor into which a harmonic current flows. In the case of a filter reactor, by adjusting the combination with the capacitor, it is possible to freely select the resonance frequency, for example, setting the inflowing harmonic as an 11th harmonic, a 13th harmonic, a 23rd harmonic, etc. Furthermore, by adjusting the configuration of the filter circuit, there may be cases where a plurality of harmonic currents flow in such as the fifth harmonic and the seventh harmonic in addition to the fundamental wave current, but the present invention is similarly applicable.

Claim 1:
A temperature increase testing method for a reactor (L1), characterized by comprising:
a step (S3) of calculating a target copper loss (Wcut) based on a copper loss (Wcu21) during energization of a fundamental wave current at a predetermined current value and respective copper losses (Wcu22m) during energization of respective harmonic currents of predetermined orders at predetermined current values;
a step (S4) of calculating a target iron loss (Wfet) based on an iron loss (Wfe21) during energization of the fundamental wave current and iron losses (Wfe22m) during energization of the respective harmonic currents;
a step (S5) of calculating a frequency and a current value of a current that creates the target copper loss (Wcut) and the target iron loss (Wfet), respectively as a test frequency (fex) and a test current value (Iex); and
a step (S6) of energizing the reactor (L1) with a test current having the test frequency (fex) and the test current value (Iex), until a temperature of a predetermined part of the reactor (L1) becomes constant.