JPH0352586B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrical loss measuring method, and particularly to an electrical loss measuring method suitable for measuring iron loss or eddy current loss of a sample to be measured with high accuracy. When current is passed through the conductor of the power cable, eddy currents flow in the steel material adjacent to the power cable or the metal sheath of the power cable due to the magnetic velocity generated by the current, and a commensurate loss occurs. If these losses are large, the allowable current of the power cable will be limited. Therefore, accurately measuring the core loss, sheath loss, etc. of these materials is an important issue in power cable design. Conventional methods for measuring iron loss and the like include a temperature rise method and a circuit loss measurement method. The temperature rise method measures the temperature rise of the sample after passing a current through the current-carrying circuit to determine iron loss, etc. However, this method is easily affected by outside air conditions and requires multiple temperature measurement points. It has the disadvantage of being necessary. In addition, the circuit loss measurement method calculates the loss in the current-carrying circuit when the sample is installed and when the sample is not installed with the current flowing in the circuit, and calculates the loss of the sample from the difference between the two. Since the loss of the circuit itself is large,
The disadvantage is that the measurement error increases. The present invention has been made in view of the above, and its purpose is to provide an electrical loss measuring method that can easily and highly accurately measure the iron loss or eddy current loss of a sample to be measured. It's about doing. The present invention is characterized by providing a current carrying circuit in which a mutual reactor and two current transformers are inserted, and installing a search coil that detects the magnetic flux generated when alternating current is passed through this current carrying circuit. a first variable resistor connected in parallel to the secondary circuit of the mutual reactor and a second variable resistor connected to the secondary side of one of the two current transformers. The difference in output voltage when the sample to be measured is not installed in the vicinity of the current-carrying circuit and when it is installed in the vicinity of the current-carrying circuit and the secondary current of the other current transformer among the two current transformers described above are calculated as follows: In the method for measuring the iron loss or eddy current loss of the sample to be measured using the method, the first and second variable resistors are connected in series to the search coil when the sample to be measured is not installed near the energized circuit. the first and second circuits so that the output voltage of the circuit becomes zero.
The point is to adjust the variable resistor. Generally, alternating current loss is determined as the inner product of the voltage drop in a current-carrying circuit and the current flowing, and the iron loss of steel materials installed in the vicinity is also measured as part of the calculation. By the way, the total voltage drop is the sum of the voltage related to iron loss and the voltage not related to iron loss, so
If the voltage unrelated to iron loss is offset by adding another circuit and made virtually zero, the total voltage drop can be made into only the voltage component related to iron loss, and the AC loss calculated from this can be expressed as iron loss. It becomes possible to measure iron loss, and a highly accurate iron loss measurement circuit (means) can be realized. An embodiment of the method of the present invention will be described in detail below with reference to the drawings. The figure is a circuit diagram showing an example of a measuring device for explaining an embodiment of the measuring method of the present invention, and shows an example of single-phase measurement. First, two conductors 1 are laid,
One end of the two conductors 1 is short-circuited, and a current-carrying transformer 2 is connected between the other ends to form a current-carrying circuit. Next, connect the voltage lead wire (insulated wire) to the outer circumference of conductor 1.
3 is spirally wound at a constant pitch to form a search coil that detects only a suitable portion of the magnetic flux generated when the current is applied to the current-carrying circuit. In addition, a mutual reactor 4 and current transformers 5 and 6 are inserted into the above-mentioned energizing circuit, and a variable resistor 7 connected in parallel to the secondary circuit of the mutual reactor 4 and a standard resistor 8 are connected to the secondary side of the current transformer 5. The variable resistors 9 connected in parallel are each connected in series to the voltage lead wire 3,
The output voltage of this circuit is input to a power meter 10. On the other hand, the energizing current of the energizing circuit is input to the power meter 10 via the current transformer 6. Next, the measurement method will be explained. A current I is passed through the current carrying circuit from the current carrying transformer 2, and the variable resistors 7 and 9 are adjusted so that the input voltage V input to the power meter 10 from the voltage lead wire 3 and the circuit of the variable resistors 7 and 9 becomes zero. . Input voltage V at this time
Monitoring is performed using an oscilloscope 11. In this case, the output of the power meter 10 becomes zero. In this state, the sample to be measured 12 is installed at a predetermined position near the voltage lead wire 3, and the power meter 10 at that time is
The eddy current loss (or iron loss) of the sample to be measured 12 is measured from the output. According to the above-described measuring method according to the present invention, the eddy current loss or iron loss of the sample to be measured 12 can be easily measured with high accuracy. Moreover, if a high-precision amplifier is installed before the power meter 10, even minute losses can be measured. Table 1 shows that the sample to be measured 12 is 75 x 40 x 900 (unit:
mm) channel steel, carrying current 2000A (frequency 50Hz),
This figure shows a comparison of measurement results between the conventional circuit loss measurement method and the measurement method according to the present invention when the distance from the current-carrying conductor of the sample 12 to be measured is 80 mm.

[Table] Data without sample.
From the results in Table 1, it can be seen that according to the measurement method according to the present invention described above, the error is significantly smaller than in the conventional circuit loss measurement method, and highly accurate measurement is possible. In addition, although the above-mentioned example shows the measurement results of iron loss, it goes without saying that the same applies to measurements of sheath loss (eddy current loss) and the like. As explained above, according to the present invention, iron loss or eddy current loss of a sample to be measured can be easily measured.
This has the effect of being able to measure with high precision.

[Brief explanation of drawings]

The figure is a circuit diagram showing an example of a measuring device for explaining an embodiment of the electrical loss measuring method of the present invention. 1: Conductor, 2: Current transformer, 3: Voltage lead wire (search coil), 4: Mutual reactor, 5,
6: Current transformer, 7, 9: Variable resistor, 10: Power meter, 12: Sample to be measured.

Claims (1)

[Claims] 1 An energizing circuit in which a mutual reactor and two current transformers are inserted is provided, a search coil is installed to detect the magnetic flux generated when an alternating current is passed through the energizing circuit, and the search coil is connected to the mutual reactor. A first variable resistor connected in parallel to the secondary circuit and a second variable resistor connected to the secondary side of one of the two current transformers are connected in series, The measurement target is measured using the difference in output voltage when the measurement target is not installed near the energized circuit and when the measurement target is installed in the vicinity of the current-carrying circuit, and the secondary current of the other current transformer of the two current transformers. In the method for measuring iron loss or eddy current loss of a sample, the first and second search coils are used when the sample to be measured is not installed near the energized circuit.
An electrical loss measuring method characterized in that the first and second variable resistors are adjusted so that the output voltage of a circuit in which the variable resistors are connected in series becomes zero.