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The method of the material curve can be completed in the following three steps

1 Introduction
When conducting voltage transformer test, it is very important to understand the working state of the voltage transformer. If the voltage transformer works in saturation, it will lead to serious aging, noise increase, etc. If the voltage transformer works in the linear region, and The function does not work well. Therefore, obtaining the magnetization curve of the voltage transformer and understanding the position of the working point helps the worker to better understand its working status.
In general, the magnetization curve of the voltage transformer is the Φ-i curve. This article describes two methods to obtain the magnetization curve. One is to use the method of electromagnetic material analysis software to simulate and obtain, and the other is to use the test operation method. Get it.
2 Method for obtaining magnetization curve using electromagnetic material analysis software
2.1 Test procedure
The use of electromagnetic material analysis software to obtain the magnetic material curve can be accomplished in the following three steps.
The first step is to use ANSYS, an electromagnetic material analysis software, to make a calculation model and input various parameters for calculation. These parameters include the number of turns of a primary coil, the number of turns of a secondary coil, the magnetic permeability of the core, and the surrounding gas. The gap and the magnetic permeability of the coil are calculated and the voltage transformer is calculated on the secondary side carrying the rated load (the rated load of the secondary side can be obtained from the nameplate of the transformer) and the secondary side under no load. The primary side of the device simulates the injection of a DC current value of each value, ie, a DC current of 0~2 A, to ensure that the voltage transformer reaches a deep saturation state, thereby obtaining a true magnetization curve. The choice of DC current size depends on the actual situation of the transformer. In principle, it is necessary to ensure that the value selected near the inflection point is more, and some values that exceed the inflection point must be selected in order to be able to simulate the voltage transformer core to the maximum extent. Magnetization curve.
Step 2: Make the value of the magnetic potential A corresponding to the transformer under various DC currents in the software, and then use the formula ∫lAdl=Ф to find the value of the flux Ф at a given current value. .
The third step: According to the value of the magnetic flux Φ obtained and the value of the DC current I that causes the magnetic flux, the magnetization curve of the transformer can be obtained through corresponding calculation.
2.2 Analysis of test results
Using the ANSYS electromagnetic material software simulation method, the following data can also be obtained: the distribution of magnetic materials inside the voltage transformer, the distribution of magnetic induction intensity inside the voltage transformer, and the core of the voltage transformer coil corresponding to the current value The magnetic material strength and the magnetic induction value of the different positions.
First of all, in the test to do a good job of the voltage transformer wiring diagram, the wiring diagram is divided into two cases, one is the voltage transformer carrying the rated load case, the other is the case of no-load voltage transformer, the circuit used in the test The model diagram is shown in Figure 1. In the figure, R1 is the power supply resistance, L1 is the power supply inductance, L2 is the primary side equivalent inductance, and R3+L3 is the secondary side equivalent impedance.

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