A split transformer, also known as a split-core transformer, is a type of transformer designed with a split core, allowing it to be easily separated into two halves. This innovative design enables convenient installation and maintenance, particularly in situations where traditional transformers may pose challenges.
In a transformer, the low-voltage coil is split into two or more parts of equal rated capacity. There is no electrical connection between the split coils, and only a weak magnetic connection.
Each branch of the split winding can run separately, or can run in parallel at the same rated voltage. After the low-voltage coil splits, the short-circuit impedance between the high-voltage coil and the split part of the low-voltage coil can be greatly increased, and the short-circuit impedance between the low-voltage split coil can be well restricted, so the split transformer is widely used in the power system.
According to its structure, the difference between the split transformer and the ordinary transformer is only the low-voltage coil itself on the iron core column, the low-voltage coil of the split transformer is not in series or parallel, and the beginning and the terminal are respectively led out.
Four, the equivalent circuit of the split transformer
Three-phase winding double split transformer, because each phase can be regarded as 3 winding, its equivalent circuit can be expressed by the general star equivalent circuit.
Five, the special parameters of the split transformer
1. When several branches of the split winding are connected in parallel to form a total low-voltage winding that operates against the high-voltage winding, it is called ride-through operation. At this time, the short-circuit impedance of the transformer is called ride-through impedance.
2. When a branch of the low-voltage split winding operates to the high-voltage winding, you operate as a half-crossover. At this time, the short-circuit impedance of the transformer is called half-crossover impedance.
3. When one branch of the split winding runs against the other branch, it is called split operation. At this time, the short-circuit impedance of the transformer is called split impedance.
4. The ratio of split impedance to crossover impedance is called split coefficient, which is one of the basic parameters of split transformer, generally 3-4.
5. Three-phase double-winding double-split transformer, each phase has three windings: a non-split high-voltage winding, which has two branches but is always connected in parallel and is actually one winding; two identical low-voltage split windings. Therefore, we can imitate the three-winding transformer and obtain an equivalent circuit composed of three equal impedances. According to the definition of split impedance, the split impedance is the impedance between the two branches, which is equal to the sum of the short-circuit impedances of the two branches. Considering the symmetry of the branch arrangement of the split winding, the short-circuit impedance of each branch is equal, equal to one-half The splitting impedance is equal to one-half the splitting coefficient times the crossing impedance. The crossover impedance is the impedance between the high-voltage windings after the two branches are connected, that is, the crossover impedance is equal to the sum of the short-circuit impedance of the high-voltage winding and half of the branch short-circuit impedance. Therefore: the short-circuit impedance of the high-voltage winding is equal to the crossover impedance minus one-half the branch short-circuit impedance; and the branch short-circuit impedance is equal to one-half the crossover impedance times the splitting coefficient, so the short-circuit impedance of the high-voltage winding is equal to one minus four One time the splitting factor, multiplied by the crossover impedance.
Six, the operation characteristics of the split transformer
Since the split transformer has a large reactance, large-unit power plants use split transformers as factory transformers and starting transformers, which have the following advantages in operation:
(1) Limit short-circuit current significantly. When one branch of the split winding is short-circuited, the short-circuit current supplied by the power grid through the semi-crossover reactance of the split transformer is larger than the ride-through reactance, so the short-circuit current supplied is smaller than that of the two-winding transformer. At the same time, the other branch of the split winding is short-circuited by the motor. The feedback current at the point is also reduced a lot due to the limitation of the split winding. This ensures the short-circuit stability of the electrical equipment on the factory bus.
(2) When one branch of the split winding fails, the bus voltage of the other branch decreases relatively little. At the same time, when the motor of one branch of the split winding starts automatically, the voltage of the other branch is almost unaffected. This improves the reliability of half the load supplied by the factory bus.
In conclusion, split transformers offer a multitude of advantages that make them a preferred choice for various applications. From their ease of installation and flexibility in retrofitting to their space-saving design and enhanced safety features, split transformers deliver efficiency, reliability, and cost-effectiveness. As electrical systems continue to evolve, split transformers remain a versatile solution for meeting the demands of modern infrastructure. Whether in commercial, industrial, or utility settings, the benefits of split transformers underscore their significance in ensuring efficient power distribution and maintenance.
