A transformer converter is an electronic device that moves energy between connections magnetically without any moving parts, and it alters, in certain specific ways, an electronic current. Transformer converters are used for changing voltages and for dispersing electrical energy to different unconnected circuits.
A transformer can be used for converting a very high voltage output that would otherwise be destructive to a system into a more manageable supply of power that a system can safely use. Likewise, it can convert a large amount of low-voltage energy into a high voltage current, should a system that it is attached to need a greater amount of power.
Transformers are also capable of isolating electrical signals across disconnected circuits, allowing a single power source to provide energy to multiple systems through it. This is vital to any system that uses multiple different circuits or machinery to keep the devices independent.
A transformer can only perform certain operations to certain kinds of electrical signals. It cannot change the voltage or current of a direct current connection, and it cannot change the frequency of an alternating current. However, transformers are often paired with components that can do these jobs for them and then feed the energy back into them to achieve the desired effects, so these functions are ultimately not important to a transformer.