A schematic diagram is a graphical representation of an electrical or electronic circuit. Schematic diagrams use standard electrical symbols which are generally drawn to represent the types and operation of the components they symbolise. Magnetic coils can take on many forms as an inductor, a winding, a choke, a solenoid, or the coils of a transformer with or without a magnetic core, so the graphical symbol of these components must demonstrate that are indeed coils of wire and not just a sequence of semicircles or loops.
While the schematic symbol of a transformer may look like two coils (called windings) placed next to each other, the magnetic coupling and orientation between these two coils is also indicated within its schematic symbol. Some coil symbols can be labeled with letters and/or numbers to indicate their electrical connections or dots to indicate polarity.
Dot convention markings use dots on the transformer schematic symbol as a way of specifying the winding direction between input and output and therefore the polarity between windings. Phase-indicating dots are marked on each winding of a common core with their position relative to each other showing whether the instantaneous voltages and currents of each winding rise and fall together indicating zero phase shift (0o), or whether one voltage and current is rising while the other is falling, indicating 180 degrees of phase shift between them.
Either way, the electrical schematic symbols for transformers, inductors and coils offer a simple and visual way of indicating which components are used with in a circuit design. There are many different standard transformer configurations each with its own transformer schematic symbol, but the individual graphical symbols of inductors and transformers given below along with a brief description and explanation are some of the more common ones we use daily.
Updated 4 November 2021.