ring coil transformer?

I scrapped kind of odd ac unit. In it was s large donut shaped inductor covered in plastic.
it contained almost five pounds of #3 copper windings. My question is what the purpose
this transformer is, why use it over a standard transformer. Any thought? This is also known
as a toroidal transformer.

Originally Posted by scrapdaddyj

I scrapped kind of odd ac unit. In it was s large donut shaped inductor covered in plastic.
it contained almost five pounds of #3 copper windings. My question is what the purpose
this transformer is, why use it over a standard transformer. Any thought? This is also known
as a toroidal transformer.

I've found the same ones in large speakers/amps

Could be a Current Transformer (CT), more of a measuring device, to monitor and/or control the current in a circuit. Did it have a single, large conductor, running through the middle of the "Doughnut" hole?

A electrical transformer is used in almost every type of electrical device, starting at the power generating station, at every connecting point along the power grid and into just about any device that requires the voltage up or down. Transformers are used as the name suggest, transfers electrical energy. Step up or step down the most common type (increase or decrease voltage or current). They can be used to provide multiple circuits of different voltages (power supplies). Because there's no physical contact between primary and secondary of a transformer, applied as a safety, isolation and surge protection type transformers. Simply there are many uses and types of transformers.

Transformers are also "noisy" devices, inducing frequency interference (harmonic hum) into circuits. This is where Toroidal Transformer is best used, they produce less induced noise into a circuit (EMI - electromagnetic interference). They are also denser due to circular design, a space saver, as traditional transformers use more space.

Without picture or more details really hard to say what type of transformer you have. There are two type of round doughnut shaped, toroidal and current (CT). You state the device was a AC unit, is it single phase or three phase? Also you asked: "My question is what the purpose this transformer is, why use it over a standard transformer." I see no obvious use for a toroidal transformer on a AC unit. A three phase motor would use a current transformer to prevent damage to a expensive three phase motor.

Can you read a part number on the transformer, the doughnut one?