Amorphous Nanocrystalline Core Structure
Solid or Split
CT cores can be of a solid (closed) or split (open) type. The solid/split core defines how the CT core is designed, and how it can be installed. Solid core CTs feature a closed loop, which the primary conductor must be passed through.
Split core CTs can be temporarily opened to facilitate easier installation. When using a split core CT, the primary conductor need not be disconnected to install the CT, and in most cases, the conductor can continue to carry current while the CT is being installed. Split core CTs have a large advantage in installations where shutdowns are not practical or economical. However, because of the added manufacturing complexity, split core CTs carry a large price premium. Likewise, because of the inherent “gap” associated with the CT opening mechanism, split core CTs tend to have lower accuracy and worse phase shift performance compared to a similar solid core CT.
Considering the magnetic core loss is very low, the split amorphous cores or split nanocrystalline cores are very suitable for distribution transformers. A distribution transformer or service transformer is a transformer that provides the final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer.
|Close Loop||Solid Cores|
|Open Loop||Split Cores (Cut Cores)|
Shapes and Encapsulations
Whether solid CT, or split CT, there are different shapes of cores for different applications. Usually circular cores are the most popular and the manufacturing cost of such cores is very low. Rectangular cores and oval cores are used for special requirements, and the price is much higher as toolings is usually required to produce them.
The variety of encapsulations, or appearance of CT Cores are also many. You can choose Epoxy Resin Coating, Plastic / Stainless Steel / Aluminum / Bakelite Box, or Crepe Paper Wrapped and so on, according to the size of require amount.
Bushing type nanocrystalline core have a very thin build. So, it may be easily deformed during process. So, we need some method to protect the bare core.
Plastic Box has the advantage of labor cost, because it’s easy to assemble. But if the required size is not available, and you had to develop a new plastic mold to produce the boxes, the total cost will be much higher than other options.
Stainless Steel Box is suitable for large size cores, as they can protect the inside core very well. We’ll use resin casting method to make the finished cores strong. Resin casting is a method of plastic casting where a mold is filled with a liquid synthetic resin, which then hardens.
We choose aluminium boxes / cases to make the protect the bare nanocrystalline cores inside. For small lot, there’s one advantage, i.e, we can manufacture the boxes without metal stamping dies.
For small quantity products or samples, Epoxy Resin Coating, or Crepe Paper Wrapped is a good choose, as the lead time is short. But Crepe Paper Wrapped can not be applied to small cores, as the crepe paper is wrapped manually.
|Epoxy Resin Coating||Contaminate The Environment|
|Aluminum||Good Mechanical Protection|
|Stainless Steel Box||High Cost|
|PBT / DMC Box||Suit For Mass Production|
|Crepe Paper Wrapped||Low Cost For Small Quantity|