What are the factors that affect the error of the current transformer?

First, internal parameters are the main factors leading to error.

1. The internal resistance R2 and leakage reactance X2 of the secondary coil will have a great impact on the error. If R2 becomes larger, the specific difference and angular difference will also become larger. To reduce the error, you need to reduce the R2 and X2 values.

The internal resistance R2 and leakage reactance X2 of the secondary coil are relatively small compared with the values of the secondary load Rfh and Xfh. Therefore, the influence of the value of R2 and X2 on the error is not great, but the influence on the transformer with small capacity is obvious.

2, reduce the excitation current, can effectively improve the ratio and Angle difference. If the magnetic flux density of the iron core is relatively small under the action of the transformer without compensation, the reduction of the magnetic flux density will lead to the decrease of the magnetic permeability coefficient. Even if the excitation current is reduced by a small amount, the impact on the magnetic flux density will be greater.

3. The influence of the number of coil turns on the error. The number of turns of the coil also needs to be increased, and increasing the number of turns can reduce the flux density, so as to improve the error. The increase of coil turns will also lead to the increase of copper consumption, resulting in the reduction of dynamic stability times, and the increase of saturation times.

4, reduce core loss and improve permeability. When the magnetic flux density of the core does not change, the reduction of the core excitation ampere turns and loss ampere turns will improve the ratio and Angle difference, through the use of excellent magnetic materials, and the selection of appropriate annealing process can effectively improve the permeability, and reduce the loss.

Second, the error caused by the operation process

After the transformer is finalized, the internal parameters have been determined, and the error will be affected by the secondary current, secondary load, power factor and frequency. These factors are also the expression of external factors.

1. The error caused by the change of current frequency is complicated. If the frequency change is too large, the error caused by the frequency should be considered. The change of frequency will not only affect the loss of the core and the density of magnetic flux, but also affect the reactance value of the secondary load.

2, when the primary current decreases, the magnetic flux density will also be affected by the proportion and reduce, when in the state of low magnetic flux density, excitation ampere turns to reduce the reading than the magnetic flux density to reduce slowly, resulting in the value of the ratio and Angle difference will become larger.

3, the power factor of the secondary load once the Angle difference will increase, but the ratio will be reduced. As far as the saturation factor is concerned, the saturation factor of 0.8 is generally required. If the power factor becomes larger or smaller, it will cause the saturation factor to become larger.

The factors that affect the error of current transformer are mainly shown in two aspects. After understanding the error, how to reduce the error? We found that the excitation current is the main factor leading to the error, so the error can be reduced by reducing the excitation current, such as increasing the cross-sectional area of the core, shortening the length of the magnetic circuit, choosing materials with high permeability as the core, limiting the secondary load, increasing the ratio of variation appropriately and so on.