How to differentiate between a contactor symbol and a thermal relay symbol?

The contactor has a simple rectangular coil, while the thermal relay has a notched symbol representing the thermal bimetal.

What do the numbers 13-14 and 95-96 mean on diagrams?

13-14 generally designates an NO (Normally Open) holding contact on a contactor, while 95-96 designates the NC (Normally Closed) safety contact of a thermal relay.

What is the symbol for an emergency stop button?

It is an NC contact push button represented by a 'mushroom' with a mechanical latching device.

Electrical Engineering Symbols Guide: Thermal Overload Relay, Contactor and Motor

In the field of industrial automation and electrical engineering, mastering standardized symbols (IEC 60617) is fundamental for reading and designing professional electrical diagrams. This article details the critical symbols for motor protection.

⚡ Quick Answer

Standardized electrotechnical symbols allow for a universal reading of industrial diagrams. The contactor is represented by a coil (K) and power contacts, the thermal relay by a bimetal symbol associated with a control contact (95-96), and the motor by a circle containing the letter M.

1. The Thermal Relay Symbol (F1)

The thermal relay is represented by three bimetallic strips in series on the power side and auxiliary contacts (95-96 NC and 97-98 NO) for control.

IEC Symbol: Rectangle crossed by three broken lines (representing the bimetallic strips).
Function: Protection against prolonged overloads.

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2. The Contactor Symbol (KM1)

The contactor is the power component controlled by a coil (A1-A2).

3. Interactive Diagram: Direct-on-line (DOL) Motor Starter

Here is a real simulation of a complete industrial assembly. Observe the physical connection between the push button, the KM2 contactor, and the thermal protection relay.