Standard current transformers are used as current transformer calibration standards in the error test of transformers
The standard current transformer consists of a primary coil, a secondary coil, a core, an insulating support, and an outgoing terminal. The core of the current transformer is made up of silicon steel sheets. The primary coil is connected in series with the main circuit, and through the measured current I1, it generates alternating magnetic flux in the core, so that the secondary coil
The corresponding secondary current I2 (which is rated at 5A) is induced. If the excitation loss is neglected, then I1n1 = I2n2, where n1 and n2 are the turns of the primary and secondary coils, respectively. The current transformer has a current conversion ratio of K=I1/I2=n2/n1. Since the primary coil of the current transformer is connected in the main circuit, the primary coil must be grounded to an insulating material suitable for the primary line voltage to ensure the safety of the secondary circuit and the human body. The secondary circuit is composed of a secondary coil of the current transformer, a meter, and a current coil of the relay in series. Current transformers can be roughly divided into two categories, current transformers for measurement and current transformers for protection.
In the supply and supply of electricity, the current varies greatly, ranging from a few amps to tens of thousands of amps. In order to facilitate the measurement of instruments and meters, it is necessary to convert to a relatively uniform current, and the voltage on the supply line is relatively high. For example, direct measurement is very dangerous for instruments, meters and people. The current transformer designed for this purpose acts as a variable current and electrical isolation.