Reading and drawing electrical diagrams is part of the basic course. Here are the diagram types (circuit diagram, main circuit/control circuit, single-line versus multi-line), the graphical symbols according to DS/EN 60617 and the reference designation system (=installation / +location / −component) according to IEC/EN 81346 — with a motor starter diagram read step by step.
Introduction
An electrical diagram is the trade's common language. If you can read a diagram, you can understand a system you've never seen before — and if you can draw one, the next person can take over your work. Diagrams and reference designations are standardised, so they mean the same across companies and countries. The governing standards are DS/EN 60617 (graphical symbols), IEC/EN 81346 series (reference designations) and DS/EN 61082 (preparation of documents).
The diagram types
There are several diagram types, each with its purpose. The type is chosen based on what you need the drawing for — to design, build, connect or troubleshoot.
- 01Overview/single-line diagram: the entire system simplified, where a multi-line system is drawn as one line. Provides overview — panel layout, groups, main routes.
- 02Circuit diagram (multi-line): the electrical function drawn in full, conductor by conductor. Used to understand and troubleshoot how the circuit WORKS.
- 03Main circuit diagram: the power circuit — the route where the large current flows (supply, fuse, contactor, motor).
- 04Control circuit diagram: the control circuit — buttons, relays, contactor coils and auxiliary contacts that determine WHEN the main circuit is switched.
- 05Installation drawing: symbols placed on a floor plan — where outlets, fittings and switches are physically located in the building.
- 06Connection/terminal table: which conductor goes to which terminal — used during physical connection.
Graphic symbols — DS/EN 60617
Components are drawn with standardised symbols after DS/EN 60617. Knowing the symbol set is like being able to read the alphabet — without it you cannot read the drawing. Examples of common symbols:
- 01Contact/switch: a breaking line over a contact point; closing contact (NO) and breaking contact (NC) are drawn differently.
- 02Circuit breaker: a rectangle in the circuit diagram; automatic circuit breaker has a special symbol with a tripping mechanism.
- 03Contactor coil: a rectangle (the coil) whose contacts are controlled elsewhere in the diagram and bear the same designation (e.g. K1).
- 04Motor: a circle with M and type designation (e.g. M 3~ for a three-phase motor).
- 05Earth and protective conductor: the well-known earth symbols where PE has its own symbol.
- 06Lamp/signal, push (with return spring), relay, transformer — each with its unique symbol.
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