· A transformer is used to transform from one voltage to another.
· The voltage ratio is proportional to the turns ration. Current is inversely proportional to the turns ratio.
· The power ratio of an ideal transformer is 1:1. In other words, if the voltage goes up, the current must go down.
· Transformers only work with AC, Alternating Current.
· The dots can be thought of as voltage polarity.
· When current flows into the dot on the primary side, an induced current flows out of the dot on the secondary.
· The voltage is in phase at the dots, but the current is flowing in the opposite direction.
When configured as a common mode choke, a transformer is seen as a low impedance to differential current and high impedance to common mode current.
· When common mode current flows through the windings, the flux adds, creating more inductance.
· When differential current flows through the windings, the flux cancels, reducing the inductance.