Although“ current sensor ”The terms "current transformer" and "current transformer" can usually be used interchangeably, but theoretically, there are some subtle differences between them. The main function of current transformer is to change the current to different levels and increase or decrease it according to the application. On the other hand, sensors are mainly used to measure current. It converts the current into a simple recording format, usually voltage signal.

Defect of actual current sensor

Like any physical device, a real current sensor will have defects. The two most important error variables you should remember are:

1. Conversion error:

Due to various factors inherent in theoretical idealization, the actual conversion rate will deviate from the ideal rate. These factors include the assumption that a linear magnetic circuit has infinite permeability and negligible resistance in the winding. In addition, the irregularity of materials can also lead to deviation.

The conversion error is usually expressed as a percentage of the measured value. The left figure in Figure 2 shows the transformation error of AC signal within a certain frequency range. The green and blue lines represent different devices.

Example: When CT 100 is used to measure a 30 kHz 20 amp AC signal, the conversion error is 0.5000%. Therefore, the final result will be adjusted to 19.9 amps to account for this error.

2. Phase error:

The phase between the primary and secondary currents may also deviate. The main reason is the electronic running time in the equipment. Angular error (also known as angular accuracy or phase error) represents the difference of this phase in degrees. The right figure in Figure 2 shows the angular error (in degrees) along the frequency range. The green and blue lines represent different devices.

Note: Angle error is particularly important in active power calculation. In order to ensure the accuracy of the results, the phase angle error must be compensated.