The application of current transformers is extensive. Today, Weikewei Technology introduces the following four wiring methods.

1. One phase wiring

The current passing through the current coil in this wiring method reflects the current of the corresponding phase in the primary circuit. Usually used for load balancing in three-phase circuits such as low-voltage power lines, for measuring current, electrical energy, or taking over load protection devices

2. Two phase V-shaped wiring

This wiring method is also known as two-phase incomplete star wiring. In relay protection devices, it is called two-phase relay wiring. In neutral ungrounded three-phase three wire circuits, it is widely used for measuring three-phase current, electrical energy, and for overcurrent relay protection. The current on the common line of the two V-shaped connections reflects the phase current of the phase that is not connected to the current transformer.

3. Two phase current difference wiring

In relay protection devices, this wiring is also known as two-phase one relay wiring. This wiring method is suitable for overcurrent relay protection in three-phase three wire circuits where the neutral point is not grounded. The current value on the common line of the secondary side of the current transformer in this wiring method is 1.73 times the phase current (root three, note: may not be displayed earlier).

4. Three phase star connection

The three current coils in this wiring method precisely reflect the currents of each phase. It is widely used in i-phase four wire systems with generally unbalanced loads, as well as in three-phase three wire systems with potentially unbalanced loads, for measuring three-phase currents, electrical energy, and overcurrent relay protection.

Wiring method of current transformer: The wiring method of current transformer is determined according to the operating requirements of the load it is connected to. The most commonly used wiring methods are single-phase, three-phase star, and incomplete star.

Rated transformation ratio and error: The rated transformation ratio KN of a current transformer refers to the rated current ratio of the current transformer. Namely: KN=I1N/I2N

When the primary current of a current transformer varies within a certain range, it is generally specified as 10-120% I1N. The secondary current should vary proportionally, and the primary and secondary voltages (or currents) should be in phase. However, due to factors such as internal impedance, excitation current, and losses in transformers, errors occur in the ratio and phase, which are respectively referred to as ratio difference and angle difference.

The ratio difference is the ratio of the difference in magnitude between the converted secondary current and the primary current to the latter, that is, fI is the ratio difference of the current transformer. When KNI2>; When I1, the ratio difference is positive, otherwise it is negative.

For current transformers without compensation measures, the ratio difference is negative and the angle difference is positive. The absolute value of the ratio difference and the angle difference both decrease with increasing current.

The use of compensation methods can reduce the error of transformers. Usually through電流互感器Add additional windings or iron cores, as well as connect corresponding resistors, inductors, and capacitors to compensate. The commonly used compensation methods include turn compensation, fractional turn compensation, small iron core compensation, parallel capacitor compensation, etc.