JP7568909B2 - Temperature rise detection method, transformer and transformer device - Google Patents

Description

The present invention relates to a method for detecting a temperature rise in a transformer, a transformer, and a transformer device.

In transformers, the temperatures of the iron core, copper wires, and insulators rise due to iron loss and copper loss, and in particular the deterioration of the insulators is accelerated, so temperature management inside the equipment is important for continued healthy operation. As an example of temperature management, Patent Document 1 shows a method of installing a temperature detection means (temperature sensor) in the iron core and controlling the power supply that supplies power in the event of overheating. Regarding this method, Patent Document 2 points out that a problem with this method is that the equipment becomes larger, and Patent Document 2 also shows an alternative method in which the inside of the two-part iron core is filled with resin or rubber with a large thermal expansion coefficient, and the phenomenon in which the gap in the iron core expands due to thermal expansion in the event of overheating, increasing the excitation current, is utilized.

JP 2002-281748 A JP 2019-186991 A

However, the method described in Patent Document 2 requires a certain amount of thermal expansion material, which adds to material costs, and also requires an additional step of filling the core with the thermal expansion material during the device manufacturing process, which leads to increased costs. Furthermore, if a gap is formed in the core, leakage flux may occur and enter the windings, resulting in additional eddy current loss.

The present invention has been made in consideration of the above circumstances, and aims to provide a temperature rise detection method, a transformer, and a transformer device that can detect a temperature rise in a transformer while suppressing increases in costs and iron loss.

In order to achieve the above object, the temperature rise detection method of the present invention comprises the steps of:
A transformer having a winding and an iron core using grain-oriented electromagnetic steel sheets,
Detecting the secondary voltage, the primary current, and the secondary current, respectively;
The excitation current is obtained by subtracting the secondary current converted to the primary side from the primary current. When the period of a half cycle of the secondary voltage is expressed as 0% to 100%, starting from the point at which the secondary voltage becomes 0 V, the temperature rise of the transformer is detected based on the increase in the excitation current within a range of 5% to 28%.

In the present invention, a temperature rise in a transformer is detected based on the excitation current, which reacts sensitively to the increase in compressive stress that increases with the temperature rise of the transformer. In addition, in the present invention, a temperature rise is detected based on an increase in excitation current within a range of 5% to 28% of a half-cycle period of the secondary voltage, which reacts particularly sensitively to an increase in compressive stress, so that an overheating can be detected before the increase in iron loss becomes significant, and a temperature rise in the transformer can be detected while suppressing the increase in iron loss.

The temperature rise detection method of the present invention further comprises the steps of:
A transformer having a winding and an iron core using grain-oriented electromagnetic steel sheets,
Detecting the secondary voltage, the primary current, and the secondary current, respectively;
With respect to the excitation current obtained by subtracting the secondary current converted to the primary side from the primary current, when the maximum voltage value of the secondary voltage is expressed as 100%, the temperature rise of the transformer is detected based on an increase in the excitation current in a section where the secondary voltage is within the range of 16% to 77% and the absolute value of the secondary voltage is increasing.

In the present invention, the voltage range of the secondary voltage that is particularly sensitive to increases in compressive stress is from 16% to 77%, and the temperature rise is detected based on the increase in excitation current in the section where the absolute value of the secondary voltage is increasing, so that overheating can be detected before the increase in iron loss becomes significant, and the temperature rise in the transformer can be detected while suppressing the increase in iron loss.

Moreover, the transformer of the present invention is
A stacked core having two yokes;
Two clamps for applying pressure to the two yokes, respectively;
A member for fastening the two clamps,
The transformer to which the temperature rise detection method is applied may be configured such that the member is entirely or partially made of a material having a linear expansion coefficient smaller than that of the stacked core.

According to the present invention, the member fastening the two clamps is formed from a material with a linear expansion coefficient smaller than that of the stacked core, and thus the member functions as a restraining member that restrains the linear expansion of the transformer. Therefore, when the stacked core attempts to thermally expand, the restraint by the restraining member acts on the stacked core, causing a compressive stress to act on the stacked core and increasing the excitation current. According to the present invention, unlike the method described in Patent Document 2, there is no need to fill the core with a thermal expansion member in order to detect a temperature rise in the transformer based on the excitation current, and there is also no need to allow a gap to form in the core when the temperature of the transformer rises. Therefore, it is possible to manage the temperature of the transformer while suppressing increases in costs and iron loss.

Moreover, the transformer of the present invention is
Wound core and
A member wound around the outer periphery of the wound core,
The transformer to which the temperature rise detection method is applied may be configured such that the member is entirely or partially made of a material having a linear expansion coefficient smaller than that of the wound core.

According to the present invention, the member wound around the outer circumference of the wound core is made of a material with a linear expansion coefficient smaller than that of the wound core, and the member functions as a restraining member that restrains the linear expansion of the transformer. Therefore, when the wound core attempts to thermally expand, the restraint by the restraining member causes a compressive stress to act on the wound core, increasing the excitation current. According to the present invention, unlike the method described in Patent Document 2, there is no need to fill the core with a thermal expansion member in order to detect a temperature rise in the transformer based on the excitation current, and there is also no need to form a gap in the core when the temperature of the transformer rises. Therefore, it is possible to manage the temperature of the transformer while suppressing increases in costs and iron loss.

Moreover, the transformer of the present invention is
Wound core and
A member wound around the outer periphery of the wound core;
The transformer may be a transformer to which the temperature rise detection method is applied or a transformer having the above configuration, the transformer including a heat insulating material disposed between the wound core and the member.

According to the present invention, the heat transfer from the wound core to the member wound around the outer periphery of the wound core is delayed by the insulating material, and the member rises in temperature and thermally expands later than the wound core. Therefore, when the overheating starts, the compressive force acting on the wound core increases, but after a certain time has passed, it reaches a steady state, so that excessive increases in iron loss can be suppressed. In other words, it is possible to detect a temperature rise based on an increase in excitation current caused by an increase in compressive stress, while preventing excessive increases in iron loss.

Moreover, the transformer of the present invention is
Wound core and
A member wound around the outer periphery of the wound core;
The transformer may be a transformer to which the temperature rise detection method is applied or a transformer based on the above configuration, the transformer may include a second member intermittently arranged in the circumferential direction of the wound core between the wound core and the member.

According to the present invention, the second member is intermittently arranged in the circumferential direction of the wound core between the wound core and the member wound around the outer periphery of the wound core. Therefore, even if the second member is a thermal insulating material, which has a low thermal expansion coefficient and a high elastic modulus, the binding force acting from the thermal insulating material to the wound core is partial, and the effect of delaying heat transfer and avoiding the binding of the wound core by the thermal insulating material is obtained. In addition, even if the second member is a spacer or the like using a general material instead of a thermal insulating material, the part where the spacer is interrupted contains a fluid insulating oil or the like, so that a delay occurs in the heat transfer from the wound core to the binding member in that part. In other words, the presence of the second member delays the heat transfer from the wound core to the member wound around the outer periphery of the wound core, and the temperature rise and thermal expansion of the said member occurs later than the wound core. Therefore, when the overheating starts, the compressive force acting on the wound core increases, but after a certain time has passed, the steady state is reached, and an excessive increase in iron loss can be suppressed. In other words, it is possible to detect a temperature rise based on an increase in excitation current caused by an increase in compressive stress, while preventing an excessive increase in iron loss.

Moreover, the transformer device of the present invention is
A transformer having a winding and an iron core using grain-oriented electromagnetic steel sheets;
A secondary voltage detection means for detecting a secondary voltage;
A primary current detection means for detecting a primary current;
A secondary current detection means for detecting a secondary current;
A calculation means for calculating an excitation current by subtracting the secondary current converted into a primary side from the primary current;
The transformer is provided with a temperature rise detection means for detecting a temperature rise of the transformer based on the excitation current within a range of 5% to 28% of a half-cycle period of the secondary voltage, expressed as 0% to 100% starting from the point at which the secondary voltage becomes 0 V.

According to the present invention, a temperature rise can be detected based on an increase in excitation current within a range of 5% to 28% of the period of a half cycle of the secondary voltage, which is particularly sensitive to an increase in compressive stress. This makes it possible to detect an overheat before the increase in iron loss becomes significant, and to detect a temperature rise in the transformer while suppressing the increase in iron loss.

Moreover, the transformer device of the present invention is
A transformer having a winding and an iron core using grain-oriented electromagnetic steel sheets;
A secondary voltage detection means for detecting a secondary voltage;
A primary current detection means for detecting a primary current;
A secondary current detection means for detecting a secondary current;
A calculation means for calculating an excitation current by subtracting the secondary current converted into a primary side from the primary current;
and a temperature rise detection means for detecting a temperature rise of the transformer based on an increase in the excitation current in a section where the secondary voltage is within a range of 16% to 77% when the maximum voltage value of the secondary voltage is expressed as 100% and the absolute value of the secondary voltage is increasing.

According to the present invention, the voltage range of the secondary voltage that is particularly sensitive to an increase in compressive stress is from 16% to 77%, and a temperature rise can be detected based on an increase in the excitation current in the section where the absolute value of the secondary voltage is increasing, so that an overheating can be detected before the increase in iron loss becomes significant, and a temperature rise in the transformer can be detected while suppressing the increase in iron loss.

The present invention makes it possible to detect temperature rise in a transformer while minimizing increases in costs and iron loss.

FIG. 13 is a diagram showing the relationship between the secondary voltage and the rate of increase in excitation current due to compressive stress in the embodiment of the present invention. 13 is a diagram showing the relationship between the secondary voltage waveform and the range in which the excitation current should be acquired. FIG. FIG. 2 is a diagram for explaining a transformer circuit according to the first embodiment. FIG. 4 is a flowchart for explaining a temperature rise detection method according to the first embodiment. FIG. 2 is a diagram showing an example of a transformer according to the first embodiment. FIG. 2 is a diagram showing a first modified example of the transformer according to the first embodiment. FIG. 4 is a diagram showing a second modified example of the transformer according to the first embodiment. FIG. 4 is a diagram showing a third modified example of the transformer according to the first embodiment.

The following describes an embodiment of the present invention with reference to the drawings.

The magnetic properties of grain-oriented electrical steel sheets change due to external stress. Therefore, in this embodiment, stress is generated by utilizing the thermal expansion of the iron core when overheating occurs, and overheating is detected based on the change in magnetic properties.

The characteristic of grain-oriented electrical steel sheets is most sensitive to compressive stress in the rolling direction, so this is used to detect overheating, but as the compressive stress increases, the iron loss also increases. Therefore, it is necessary to have a method that can detect overheating before the increase in iron loss becomes significant. In other words, it is necessary to use a characteristic that is more sensitive to compressive stress for detection. As a result of experimental studies, the inventors of the present invention found that when the characteristic is the excitation current of the iron core and the period of a half cycle of the secondary voltage is expressed as 0% to 100% starting from the point when the secondary voltage becomes 0V, it is most appropriate to measure the increase in excitation current within the range of 5% to 28%. The results of the experiment are shown in Figure 1. Figure 1 shows the increase rate of the excitation current when compressive stress is applied to grain-oriented electrical steel sheets. Note that Figure 1(c) is a diagram of a part of Figure 1(b) in the horizontal axis direction that is enlarged. As shown in Figure 1, the increase in excitation current with respect to compressive stress is particularly noticeable within the range of 5% to 28% of the period of a half cycle of the secondary voltage. If this range is replaced by the amplitude of the secondary voltage, when the maximum voltage of the secondary voltage is expressed as 100%, the secondary voltage is within the range of 16% to 77%, and the absolute value of the secondary voltage is increasing. If the range in which this excitation current should be measured is shown on the secondary voltage waveform, it becomes the section indicated by the arrow in Figure 2. Note that in Figures 1 and 2, the horizontal axis (time) and vertical axis (amplitude) are normalized according to the rules explained here.

An example of a specific circuit for implementing the present invention will be described with reference to FIG. 3. The transformer circuit 10 includes a power source 11, a transformer device 12, and a load 13. The transformer device 12 is provided between the power source 11 and the load 13.

The transformer device 12 includes a transformer 20, current transformers 21 and 22, shunt resistors 23 and 24, a multiplication and subtraction circuit 25, a comparison circuit 26, a zero-cross detection circuit 27, a delay circuit 28, and a control circuit 29.

Current transformer 21 is arranged on the primary side of transformer 20 and is capable of detecting the primary current (primary current waveform) ip flowing through the primary side (primary winding 31). Current transformer 22 is arranged on the secondary side of transformer 20 and is capable of detecting the secondary current (secondary current waveform) is flowing through the secondary side (secondary winding 32).

The shunt resistor 23 is connected to the current transformer 21 and converts the primary current ip detected by the current transformer 21 into a voltage. The shunt resistor 24 is connected to the current transformer 22 and converts the secondary current is detected by the current transformer 22 into a voltage. In other words, a voltage according to the primary current ip or the secondary current is is applied to the shunt resistors 23 and 24, respectively.

The multiplication/subtraction circuit 25 receives a voltage corresponding to the primary current ip across the shunt resistor 23 and a voltage corresponding to the secondary current is across the shunt resistor 24. That is, the primary current ip and the secondary current is detected by the current transformers 21 and 22 are converted into voltages and input to the multiplication/subtraction circuit 25. This allows the multiplication/subtraction circuit 25 to obtain the primary current ip and the secondary current is. In other words, the multiplication/subtraction circuit 25 obtains the measurement value of the primary current (primary current waveform) ip flowing through the primary side (primary winding 31) of the transformer 20 via the current transformer 21 and the shunt resistor 23. The multiplication/subtraction circuit 25 also obtains the measurement value of the secondary current (secondary current waveform) is flowing through the secondary side (secondary winding 32) of the transformer 20 via the current transformer 22 and the shunt resistor 24.

The multiplication and subtraction circuit 25 multiplies the measured value of the secondary current is, which is the load current, by the turns ratio between the number of turns np of the primary winding 31 of the transformer 20 and the number of turns ns of the secondary winding 32 to obtain a converted current on the primary side (see equation (1) described later). Next, the multiplication and subtraction circuit 25 subtracts the load current by subtracting this converted current from the measured value of the primary current ip to calculate the excitation current (excitation current waveform) ie.

The multiplication and subtraction circuit 25 outputs the calculated excitation current ie, and the output excitation current ie is input to the comparison circuit 26.

Meanwhile, the secondary voltage (secondary voltage waveform) vs applied to the secondary side of the transformer 20 is input to the zero-cross detection circuit 27. That is, the zero-cross detection circuit 27 is capable of acquiring a measurement value of the secondary voltage vs. Furthermore, based on the acquired secondary voltage vs, the zero-cross detection circuit 27 detects the point in time at which the secondary voltage vs becomes zero, and outputs a detection signal Sd indicating the point in time at which the secondary voltage vs becomes zero.

The detection signal Sd output from the zero-cross detection circuit 27 is input to the delay circuit 28. The delay circuit 28 delays the detection signal Sd and generates a timing notification signal St. Specifically, when the period of a half cycle of the secondary voltage vs is expressed as 0% to 100%, with the point at which the secondary voltage becomes 0V as the starting point (0%), the delay circuit 28 generates the timing notification signal St at a predetermined point (a predetermined point set in the zero-cross detection circuit 27) that is set within the range of 5% to 28% of the period.

That is, the zero-cross detection circuit 27 and the delay circuit 28 function as a timing notification circuit (timing notification means 54) that notifies the comparison circuit 26 of the timing suitable for performing the comparison described below. The timing suitable for performing the comparison refers to the timing when the period of a half cycle of the secondary voltage vs is within the range of 5% to 28% when the secondary voltage is expressed as 0% to 100% with the point at which the secondary voltage becomes 0V as the starting point (0%). The timing suitable for performing the comparison can also be said to be the timing when the secondary voltage vs is within the range of 16% to 77% when the maximum voltage of the secondary voltage vs is expressed as 100%, and when the absolute value of the secondary voltage is increasing.

The timing notification signal St output from the delay circuit 28 is input to the comparison circuit 26. Upon receiving the timing notification signal St, the comparison circuit 26 compares the excitation current ie output from the multiplication/subtraction circuit 25 with a reference value ir held internally by the comparison circuit 26 (pre-set in the comparison circuit 26), and when the excitation current ie exceeds the reference value ir, it outputs a notification signal Sc notifying that the excitation current ie has exceeded the reference value ir. The conditions under which the notification signal Sc is output are shown in the following formula (1).

By setting the reference value ir in advance to the limit value of the excitation current that increases due to thermal expansion of the iron core, the notification signal Sc is output when overheating occurs. In other words, the notification signal Sc can be said to be a signal that notifies the user that overheating has occurred. The notification signal Sc output from the comparison circuit is input to the control circuit 29.

The control circuit 29 is disposed between the power source 11 and the transformer 20. The control circuit 29 is capable of controlling the power supply to the primary side of the transformer 20. When the notification signal Sc is input (when an overheat is detected), the control circuit 29 cuts off or suppresses the power supply. In other words, the control circuit 29 is capable of controlling the power supply to the primary side of the transformer 20 based on the notification signal Sc.

The control circuit 29 may be configured to send an alert to a system that monitors the power network in which the transformer 20 is used when the notification signal Sc is input (when an overheating is detected). In other words, the control circuit 29 may be capable of outputting an alert signal to a device external to the transformer device 12 to notify that an overheating has occurred.

The transformer circuit 10 can also be represented as shown in FIG. 4. That is, as is clear from the above, the current transformer 21, the shunt resistor 23, and the multiplication/subtraction circuit 25 function as a primary current detection means 50 that detects the primary current (primary current waveform) ip. The current transformer 22, the shunt resistor 24, and the multiplication/subtraction circuit 25 function as a secondary current detection means 51 that detects the secondary current (secondary current waveform) is. The multiplication/subtraction circuit 25 also functions as a calculation means 53 that calculates the excitation current ie by subtracting the secondary current is converted to the primary side from the primary current ip. The zero-cross detection circuit 27 also functions as a secondary voltage detection means 52 that detects the secondary voltage (secondary voltage waveform) vs. In addition, the zero-cross detection circuit 27 and the delay circuit 28 function as a timing notification means 54 that determines the timing suitable for detecting the temperature rise of the transformer 20 based on the excitation current ie based on the secondary voltage vs detected by the secondary voltage detection means 52 and notifies the timing. In addition, the comparison circuit 26 functions as a temperature rise detection means 55 that detects the temperature rise of the transformer 20 based on the increase in the excitation current ie at the timing notified by the timing notification means 54. Note that the primary current detection means 50, the secondary current detection means 51, and the secondary voltage detection means 52 may use other configurations as long as they can detect (measure) the primary current, secondary current, and secondary voltage, respectively. In addition, the calculation means 53 may use other configurations as long as they can obtain the excitation current ie based on the primary current ip and the secondary current is. In addition, the temperature rise detection means 55 may use other configurations as long as they can detect the temperature rise of the transformer 20 based on the excitation current ie at a predetermined timing.

In this specification, the primary current ip, secondary current is, secondary voltage vs, and excitation current ie handled by each circuit (means) do not necessarily indicate the current value or voltage value in the transformer 20 itself, and may be standardized as necessary.

Next, a method for detecting a temperature rise in the transformer circuit 10 will be described with reference to the flowchart shown in FIG.

First, the primary current detection means 50 detects the primary current ip, and the secondary current detection means 51 detects the secondary current is (step S1).

Then, the calculation means 53 calculates the excitation current ie based on the primary current ip and the secondary current is (step S2). For example, the calculation means 53 calculates the converted current converted to the primary side by multiplying the detected secondary current is by the turn ratio between the number of turns np of the primary winding 31 of the transformer 20 and the number of turns ns of the secondary winding 32. The calculation means 53 then subtracts the converted current from the detected primary current ip to calculate the excitation current ie.

Meanwhile, the secondary voltage detection means 52 detects the secondary voltage vs (step S3).

Next, the timing notification means 54 determines the appropriate timing for the temperature rise detection means 55 to detect a temperature rise based on the detected secondary voltage vs, and transmits a timing notification signal St to the temperature rise detection means to notify the timing (step S4).

Next, the temperature rise detection means 55 judges whether the excitation current ie calculated in step S2 is increasing at the timing notified by the timing notification signal St, and outputs a notification signal Sc if it is determined that the excitation current ie is increasing (step S5). Specifically, when the timing notification signal St is transmitted from the timing notification means 54, the temperature rise detection means 55 compares the excitation current ie calculated in step S2 with a reference value ir held internally by the temperature rise detection means 55, and if the excitation current ie exceeds the reference value ir, outputs a notification signal Sc notifying that the excitation current ie has exceeded the reference value ir. Here, the case where the excitation current ie exceeds the reference value ir corresponds to a case where the temperature has risen too high. In other words, if the excitation current ie exceeds the reference value ir, the temperature rise detection means 55 judges that the excitation current ie is overheating and outputs a notification signal Sc notifying that the temperature has risen too high.

As a result of the above, it is detected that the transformer 20 has become overheated.

Note that the flow shown in the flowchart of FIG. 5 is merely an example, and the order and configuration of each process may be different. For example, the excitation current ie may be calculated based on the primary current ip and the secondary current is at the timing when the timing notification signal St is output, and the calculated excitation current ie may be compared with the reference value ir. The comparison of the excitation current ie with the reference value ir may be performed only once or multiple times within a range of 5% to 28% of the period of the half cycle of the secondary voltage vs (or within a range of 16% to 77% of the voltage range and in a section where the absolute value of the voltage is increasing), and may be performed continuously or intermittently. In other words, the timing notification signal St may notify one point (a specific time point at which the excitation current ie should be compared with the reference value ir) within a range of 5% to 28% of the period of the half cycle of the secondary voltage vs (or within a range of 16% to 77% of the voltage range and in a section where the absolute value of the voltage is increasing), or may notify a period corresponding to a plurality of points. In addition, for example, the comparison between the excitation current ie and the reference value ir may be performed at a time other than the timing at which the timing notification signal St is output (for example, always), and the notification signal Sc may be output when the excitation current ie exceeds the reference value ir at the timing at which the timing notification signal St is output. Even in this case, it can be said that the temperature rise is detected based on the increase in the excitation current ie at the timing notified by the timing notification signal St. In this embodiment, in repeatedly executing the judgment, the timing at which the increase in the excitation current ie is judged is always set to be the same time point in the period of the half cycle of the secondary voltage vs. Specifically, the delay circuit 28 and timing notification means 54 are set to always determine whether the excitation current ie exceeds the reference value ir at 15% of the half-cycle period of the secondary voltage vs. If the timing of the repeated determinations is always the same, the timing may be set to a different point other than 15% of the half-cycle period of the secondary voltage vs.

Next, the configuration of the transformer 20 will be described. In order to generate stress when the core thermally expands, some kind of restraining force is required to suppress the thermal expansion. Therefore, in this embodiment, a commonly used core fixing structure is used to obtain the restraining force. Figure 6 shows an example in which the present invention is applied to a stacked core transformer 100 as the transformer 20.

The stacked core transformer 100 includes a stacked core 110, a clamp 113, a rod 114, and a winding 115. The stacked core 110 is formed by stacking directional electromagnetic steel sheets. The stacked core 110 also includes legs 111 and a yoke 112. To fix the stacked core 110, glass tape is generally used for the legs 111 extending in the vertical direction (Y-axis direction), while clamps 113 (upper clamp 113a, lower clamp 113b) consisting of steel plate (clamp plate) 120 are used for the yoke 112 (upper yoke 112a, lower yoke 112b) extending in the horizontal direction (X-axis direction). The upper clamp 113a (steel plate 120 of the upper clamp 113a) and the lower clamp 113b (steel plate 120 of the lower clamp 113b) are fastened with a plurality of rods (fastening members) 114.

Each of the upper clamp 113a and the lower clamp 113b has two steel plates 120 and a connecting member 116 that connects the two steel plates 120. Each of the upper clamp 113a and the lower clamp 113b sandwiches the upper yoke 112a or the lower yoke 112b with the two steel plates 120 and applies pressure in the stacking direction (Z-axis direction) of the upper yoke 112a or the lower yoke 112b.
The upper clamp 113a and the lower clamp 113b may be any clamp that can apply pressure to the upper yoke 112a and the lower yoke 112b, respectively. For example, each clamp 113 may be configured to apply pressure to each yoke 112 arranged inside the U-shape by using a single steel plate 120 bent into a U-shape in cross section.

In this embodiment, the member fastening the upper clamp 113a and the lower clamp 113b, i.e., the rod 114, is made entirely or at least partially of a material with a smaller thermal expansion coefficient (linear expansion coefficient) than the grain-oriented electromagnetic steel sheets that make up the stacked core 110, so that it functions as a restraining member 114. That is, the upper clamp 113a and the lower clamp 113b are fastened by the rod 114, which serves as a restraining member 114 with a smaller thermal expansion coefficient (linear expansion coefficient) than the grain-oriented electromagnetic steel sheets. As a result, the restraining member 114 generates a force that restrains the thermal expansion (linear expansion) of the stacked core 110 in the vertical direction (Y-axis direction), and a compressive force is generated in the rolling direction of the grain-oriented electromagnetic steel sheets against the stacked core 110, which is attempting to thermally expand (linearly expand).

The material of the rod 114 may have a linear expansion coefficient in the range of -1 x 10 ^-6 /°C to 4 x 10 ^-6 /°C, for example. Specifically, the material of the rod 114 may be carbon fiber reinforced plastic (CFRP). By using carbon fiber reinforced plastic (CFRP) as the material of the rod 114, it is possible to increase the mechanical strength while keeping the linear expansion coefficient within a desired range. The linear expansion coefficient of the grain-oriented electromagnetic steel sheet of the stacked core 110 can be assumed to be, for example, approximately 13 x 10 ^-6 /°C.

(Variation 1)
Next, as a modified example, an example in which the present invention is applied to a wound core transformer 200 as the transformer 20 will be described with reference to Fig. 7. Fig. 7 is a cross-sectional view of a wound core transformer 200 to which the present invention is applied.

The wound core transformer 200 includes a wound core 210, a band 211 wound around the outer periphery of the wound core 210, and a winding 212. The wound core 210 is fixed by winding and tightening the band 211 around the outer periphery of the wound core 210.

In this modified example, the entire or at least a part of the band 211 is made of a material with a smaller thermal expansion coefficient (linear expansion coefficient) than the grain-oriented electromagnetic steel sheet that constitutes the wound core 210, and this allows the band 211 to function as the restraining member 211. In other words, by forming the member wound around the outer periphery of the wound core 210 from a material with a smaller thermal expansion coefficient (linear expansion coefficient) than the grain-oriented electromagnetic steel sheet to serve as the restraining member 211, a force is generated that restrains the thermal expansion (linear expansion) of the wound core 210, and a compressive force is generated in the rolling direction of the grain-oriented electromagnetic steel sheet against the wound core 210, which is attempting to thermally expand (linearly expand).

The material of the band 211 may have a linear expansion coefficient in the range of -1 x 10 ^-6 /°C to 4 x 10 ^-6 /°C, for example. Specifically, the material of the band 211 may be carbon fiber reinforced plastic (CFRP). By using carbon fiber reinforced plastic (CFRP) as the material of the band 211, it is possible to increase the mechanical strength while keeping the linear expansion coefficient within a desired range. The linear expansion coefficient of the grain-oriented electromagnetic steel sheet of the wound core 210 can be assumed to be, for example, approximately 13 x 10 ^-6 /°C.

(Variation 2)
Next, as another modified example, an example in which the present invention is applied to a wound core transformer 300 as the transformer 20 will be described with reference to Fig. 8. Fig. 8 is a cross-sectional view of the wound core transformer 300 to which the present invention is applied. Note that the same reference numerals will be used to designate components similar to or corresponding to those in the first modified example.

In the form of the modified example 1 shown in FIG. 7, once the temperature starts to rise, the difference in thermal expansion between the iron core and the restraining member increases, while the restraining force continues to increase, so that the iron loss also continues to increase, and the increase in iron loss may become unnecessarily large. Therefore, in this modified example, the restraining member (band) 211 wound around the outer periphery of the wound core 210 is made of a material having a thermal expansion coefficient (linear expansion coefficient) equivalent to that of the directional electromagnetic steel sheet that constitutes the wound core 210. Note that the restraining member 211 may be, for example, a steel band. In addition, a heat insulating material 320 is arranged between the wound core 210 and the restraining member 211. In other words, the heat insulating material 320 is sandwiched between the wound core 210 and the restraining member 211.

With this configuration, heat transfer from wound core 210 to restraining member 211 is delayed, and restraining member 211 rises in temperature and thermally expands later than wound core 210. For this reason, the compressive force acting on wound core 210 increases when the overheating starts, but after a certain time has passed, a steady state is reached and the compressive force becomes a constant value, making it possible to suppress an excessive increase in iron loss.
It is preferable to use a material for the heat insulating material 320 that has a thermal conductivity of 0.5 W/(m·K) or less and a low elastic modulus that does not restrict the wound core 210 .

(Variation 3)
Next, as another modified example, an example in which the present invention is applied to a wound core transformer 400 as the transformer 20 will be described with reference to Fig. 9. Fig. 9 is a cross-sectional view of the wound core transformer 400 to which the present invention is applied. Note that the same reference numerals will be used to designate components similar to or corresponding to those in Modification 2.

In this modification, the insulating material 320 described in modification 2 is intermittently arranged in the circumferential direction of the wound core 210. If the insulating material 320 used has a low thermal expansion coefficient and a high elastic modulus, the insulating material 320 may restrain the wound core 210, and the above-mentioned delay effect may not be fully obtained. Therefore, by making the insulating material 320 discontinuous as in this modification, the restraining force acting on the wound core 210 by the insulating material 320 becomes partial, and the effect of delaying heat propagation and the effect of avoiding restraint of the wound core 210 are obtained.

In this modified example, a spacer 320 made of a general material may be placed between the wound core 210 and the restraining member 211 instead of the insulating material 320. Even with this configuration, a fluid insulating oil or the like will enter the parts where the spacer 320 is interrupted (such as the gaps between adjacent spacers), causing a delay in the heat conduction from the wound core 210 to the restraining member 211 in those parts, and the same effect as in modified example 2 can be obtained.

As described above, the temperature rise detection method of this embodiment detects the secondary voltage vs, primary current ip, and secondary current is in a transformer 20 having a winding and an iron core using grain-oriented electromagnetic steel sheets, and detects a temperature rise in the transformer 20 based on an increase in the excitation current ie within a range of 5% to 28% of the half-cycle period of the secondary voltage vs, expressed as 0% to 100% starting from the point when the secondary voltage vs becomes 0 V, for the excitation current ie obtained by subtracting the secondary current is converted to the primary side from the primary current ip. With this configuration, a temperature rise in the transformer 20 can be detected based on the excitation current ie, which reacts sensitively to an increase in compressive stress that increases with a temperature rise in the transformer 20. In this configuration, the temperature rise is detected based on an increase in the excitation current ie within a range of 5% to 28% of the half-cycle period of the secondary voltage vs, which is particularly sensitive to increases in compressive stress, so that excessive heating can be detected before the increase in iron loss becomes significant, and the temperature rise in the transformer can be detected while suppressing the increase in iron loss.

In addition, the temperature rise detection method of this embodiment detects the secondary voltage vs, primary current ip, and secondary current is in a transformer 20 having a winding and an iron core using grain-oriented electromagnetic steel sheets, and detects the temperature rise of the transformer 20 based on the increase in excitation current ie in a section where the secondary voltage vs is within a range of 16% to 77% and the absolute value of the secondary voltage vs is increasing when the maximum voltage value of the secondary voltage vs is expressed as 100%. With this configuration, the voltage range of the secondary voltage vs, which is particularly sensitive to an increase in compressive stress, is 16% to 77%, and the temperature rise is detected based on the increase in excitation current ie in a section where the absolute value of the secondary voltage vs is increasing, so that overheating can be detected before the increase in iron loss becomes significant, and the temperature rise of the transformer can be detected while suppressing the increase in iron loss.

The transformer 100 of this embodiment has a stacked core 110 having two yokes 112, two clamps 113 that pressurize the two yokes 112, and a rod 114 that fastens the two clamps 113, and the whole or part of the rod 114 is made of a material having a linear expansion coefficient smaller than that of the stacked core 110. According to this configuration, the rod 114 that fastens the two clamps 113 is made of a material having a linear expansion coefficient smaller than that of the stacked core 110, so that the rod 114 functions as a restraining member 114 that restrains the linear expansion of the transformer. Therefore, when the stacked core 110 thermally expands, a compressive stress acts on the stacked core 110 due to the restraint by the rod (restraining member) 114, and the excitation current ie increases. According to this configuration, in detecting a temperature rise of the transformer based on the excitation current ie, it is not necessary to fill the inside of the core with a thermal expansion material, and it is also not necessary to form a gap in the core when the temperature of the transformer rises. This allows for temperature control of the transformer while minimizing increases in costs and iron loss.

The transformer 200 of this embodiment has a wound core 210 and a band 211 wound around the outer periphery of the wound core 210, and the entire or part of the band 211 is made of a material having a linear expansion coefficient smaller than that of the wound core 210. With this configuration, the band 211 wound around the outer periphery of the wound core 210 is made of a material having a linear expansion coefficient smaller than that of the wound core, so that the band 211 functions as a restraining member 211 that restrains the linear expansion of the transformer. Therefore, when the wound core 210 thermally expands, a compressive stress acts on the wound core 210 due to the restraint by the band (restraining member) 211, and the excitation current ie increases. With this configuration, in order to detect a temperature rise of the transformer based on the excitation current ie, it is not necessary to fill the core with a thermal expansion material, and it is also not necessary to form a gap in the core when the temperature of the transformer rises. Therefore, it is possible to perform temperature management of the transformer while suppressing increases in costs and iron loss.

The transformer 300 of this embodiment also includes a wound core 210, a band 211 wound around the outer periphery of the wound core 210, and a heat insulating material 320 arranged between the wound core 210 and the band 211. With this configuration, the heat propagation from the wound core 210 to the band 211 wound around the outer periphery of the wound core 210 is delayed by the heat insulating material 320, and the band 211 increases in temperature and thermally expands later than the wound core 210. For this reason, when the overheating starts, the compressive force acting on the wound core 210 increases, but after a certain time has passed, the state becomes steady, so that excessive increases in iron loss can be suppressed. In other words, it is possible to detect a temperature rise based on an increase in the excitation current ie due to an increase in compressive stress, while preventing excessive increases in iron loss.

The transformer 400 of this embodiment also includes a wound core 210, a band 211 wound around the outer periphery of the wound core 210, and a second member 320 arranged intermittently in the circumferential direction of the wound core 210 between the wound core 210 and the band 211. With this configuration, the second member 320 is arranged intermittently in the circumferential direction of the wound core 210 between the wound core 210 and the band 211. Therefore, even if the second member 320 is a thermal insulating material and the thermal expansion coefficient of the thermal insulating material is low and the elastic modulus is high, the restraining force acting from the thermal insulating material to the wound core 210 is partial, and the effect of delaying heat transfer and the effect of avoiding restraint of the wound core 210 by the thermal insulating material are obtained. Also, even if the second member 320 is a spacer, insulating oil or the like having fluidity enters the part where the spacer is interrupted, so that a delay in heat conduction from the wound core 210 to the band 211 occurs in that part. That is, the presence of the second member 320 delays the heat transfer from the wound core 210 to the band 211, and the band 211 rises in temperature and thermally expands later than the wound core 210. Therefore, when the overheating starts, the compressive force acting on the wound core 210 increases, but after a certain amount of time has passed, it becomes steady, so that an excessive increase in iron loss can be suppressed. In other words, it is possible to detect a temperature rise based on an increase in the excitation current ie caused by an increase in compressive stress, while preventing an excessive increase in iron loss.

In addition, the transformer device 12 of this embodiment includes a transformer 20 having a winding and an iron core made of grain-oriented electromagnetic steel sheet, secondary voltage detection means 52 for detecting secondary voltage vs, primary current detection means 50 for detecting primary current ip, secondary current detection means 51 for detecting secondary current is, calculation means 53 for calculating excitation current ie by subtracting secondary current is converted to the primary side from primary current ip, and temperature rise detection means 55 for detecting a temperature rise of the transformer 20 based on the excitation current ie within a range of 5% to 28% of the period of a half cycle of the secondary voltage vs, when the period is expressed as 0% to 100% starting from the point at which the secondary voltage vs becomes 0 V. With this configuration, a temperature rise can be detected based on an increase in excitation current ie within a range of 5% to 28% of the period of a half cycle of the secondary voltage vs, which is particularly sensitive to increases in compressive stress, so that an overheat can be detected before the increase in iron loss becomes significant, and the temperature rise of the transformer can be detected while suppressing the increase in iron loss.

The transformer device 12 of this embodiment also includes a temperature rise detection means 55 that detects a temperature rise in the transformer 20 based on an increase in the excitation current ie in a section where the secondary voltage vs is in the range of 16% to 77% and the absolute value of the secondary voltage vs is increasing when the maximum voltage value of the secondary voltage vs is expressed as 100%. With this configuration, the voltage range of the secondary voltage vs, which is particularly sensitive to an increase in compressive stress, is 16% to 77%, and a temperature rise can be detected based on an increase in the excitation current ie in a section where the absolute value of the secondary voltage vs is increasing, so that an overheating can be detected before the increase in iron loss becomes significant, and a temperature rise in the transformer can be detected while suppressing the increase in iron loss.

The above-described embodiments are merely examples for implementing the present invention. Therefore, the present invention is not limited to the above-described embodiments, and each component can be replaced, deleted, or otherwise modified within the scope of the present invention.

12 Transformer device 20 Transformer 31 Primary winding 32 Secondary winding 50 Primary current detection means 51 Secondary current detection means 52 Secondary voltage detection means 53 Calculation means 54 Timing notification means 55 Temperature rise detection means 100 Stacked core transformer 110 Stacked core 112 Yoke 113 Clamp 114 Rod (restraint member)
115 Winding 200 Wound core transformer 210 Wound core 211 Band (restraint member)
212 Winding 300 Wound core transformer 320 Heat insulating material (spacer)
400 Wound core transformer ie Excitation current ip Primary current is Secondary current vs Secondary voltage

Claims (8)

A transformer having a winding, an iron core using grain-oriented electromagnetic steel sheets, and a restraining member that generates a compressive stress on the iron core that is prone to thermal expansion ,
Detecting the secondary voltage, the primary current, and the secondary current, respectively;
As the timing for detecting the temperature rise of the transformer, a timing included in a range of 5% to 28% of a period of a half cycle of the secondary voltage expressed as 0% to 100% from the point when the secondary voltage becomes 0 V as a starting point is determined;
A temperature rise detection method in which an excitation current obtained by subtracting the secondary current converted to the primary side from the primary current is compared with a predetermined reference value at the timing, and if the excitation current, which increases due to the compressive stress generated in the iron core by the restraint member, exceeds the reference value, it is determined that an overheat has occurred . A transformer having a winding, an iron core using grain-oriented electromagnetic steel sheets, and a restraining member that generates a compressive stress on the iron core that is prone to thermal expansion ,
Detecting the secondary voltage, the primary current, and the secondary current, respectively;
As a timing for detecting a temperature rise of the transformer, a timing is determined when the secondary voltage is within a range of 16% to 77% of a maximum voltage of the secondary voltage expressed as 100% and an absolute value of the secondary voltage is increasing;
A temperature rise detection method in which an excitation current obtained by subtracting the secondary current converted to the primary side from the primary current is compared with a predetermined reference value at the timing, and if the excitation current, which increases due to the compressive stress generated in the iron core by the restraint member, exceeds the reference value, it is determined that an overheat has occurred . A stacked core having two yokes;
Two clamps for applying pressure to the two yokes, respectively;
A member for fastening the two clamps,
The member functions as a restraining member that generates a compressive stress on the stacked core that is prone to thermal expansion,
3. A transformer to which the temperature rise detection method according to claim 1 or 2 is applicable, wherein the member is entirely or partially made of a material having a linear expansion coefficient smaller than that of the stacked core. Wound core and
A member wound around the outer periphery of the wound core,
The member functions as a restraining member that generates a compressive stress on the wound core that is prone to thermal expansion,
3. A transformer to which the temperature rise detection method according to claim 1 or 2 can be applied, wherein the member is entirely or partially made of a material having a linear expansion coefficient smaller than that of the wound core. Wound core and
A member wound around the outer periphery of the wound core;
a thermal insulator disposed between the wound core and the member ,
5. A transformer to which the temperature rise detection method according to claim 1 or 2 is applied, or a transformer according to claim 4, wherein the member functions as a restraining member that generates a compressive stress on the wound core that is undergoing thermal expansion . Wound core and
A member wound around the outer periphery of the wound core;
and a second member disposed intermittently in a circumferential direction of the wound core between the wound core and the member ,
A transformer to which the temperature rise detection method according to claim 1 or 2 is applied, or a transformer according to claim 4 or 5, wherein the member functions as a restraining member that generates a compressive stress on the wound core that is undergoing thermal expansion . A transformer having a winding, an iron core using a grain-oriented electromagnetic steel sheet, and a restraining member that generates a compressive stress on the iron core that tends to thermally expand ;
A secondary voltage detection means for detecting a secondary voltage;
A primary current detection means for detecting a primary current;
A secondary current detection means for detecting a secondary current;
a timing determination means for determining, as a timing related to detection of a temperature rise of the transformer, a timing included in a range of 5% to 28% of a period of a half cycle of the secondary voltage expressed as 0% to 100% from a point when the secondary voltage becomes 0 V as a starting point;
A calculation means for calculating an excitation current by subtracting the secondary current converted into a primary side from the primary current;
and a temperature rise detection means for comparing the excitation current at the timing with a preset reference value and determining that an overheat has occurred if the excitation current, which increases due to the compressive stress generated in the iron core by the restraint member, exceeds the reference value . A transformer having a winding, an iron core using a grain-oriented electromagnetic steel sheet, and a restraining member that generates a compressive stress on the iron core that tends to thermally expand ;
A secondary voltage detection means for detecting a secondary voltage;
A primary current detection means for detecting a primary current;
A secondary current detection means for detecting a secondary current;
a timing determination means for determining, as a timing related to detection of a temperature rise of the transformer, a timing at which the secondary voltage falls within a range of 16% to 77% when a maximum voltage value of the secondary voltage is expressed as 100% and an absolute value of the secondary voltage is increasing;
A calculation means for calculating an excitation current by subtracting the secondary current converted into a primary side from the primary current;
and a temperature rise detection means for comparing the excitation current at the timing with a preset reference value and determining that an overheat has occurred if the excitation current, which increases due to the compressive stress generated in the iron core by the restraint member, exceeds the reference value .

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