What is a core type transformer?

Basically a core type transformer is one in which primary and secondary windings surround the transformer core. And transformers have two types of windings basically primary and secondary. The voltage is transferred from the primary to the secondary winding through the magnetic flux. And the core is the layer of metal that conducts the magnetic field and can also be called the main body of the transformer.

So, in this type of transformer, windings surround the core. Hence, they are called core type transformers. The part which is twisted is also known as the limb. Both the windings are mounted on separate limbs of the core. And core type transformers have only single flux path in the circuit. Also, it is worth noting that there are two types of windings on each of the primary and secondary - low voltage (LV) and high voltage (HV). In the image below, green color is LV winding and red color is HV winding. The LV winding is placed near the core and the HV winding overlaps the LV winding. As you can see, there isn't a single core; But several layers of core. This is called lamination.