Are you wondering what a thermal magnetic circuit breaker could do for your electrical installation? One-Elec explains everything you need to know about this essential protective device for your electrical panel
What is the purpose of a thermal magnetic circuit breaker?
The standard circuit breaker is always thermal magnetic in nature. It performs a dual protective function in your electrical installation. It continuously monitors the current flowing through your circuits and intervenes as soon as an anomaly is detected.
Its thermal function protects against overloads. For example, when too many devices are plugged in and too much power is consumed at once. This thermal component uses a bimetallicstrip that deforms when heated. When too much current flows, the temperature rises. The bimetallic strip deforms and breaks the circuit. This protection acts gradually, within a few seconds or minutes.
Its magnetic protection, on the other hand, protects against short circuits in case of sudden and intense current surges. This component works with an electromagnetic coil: it creates a powerful magnetic field that triggers immediate circuit opening. This reaction is ultra-fast: just a few milliseconds.
This dual mechanism protects electrical cables and connected devices. It also ensures personal safety against electrical hazards and prevents domestic and industrial accidents.
What is the difference between a residual current circuit breaker and a thermal magnetic circuit breaker?
A residual current circuit breaker (RCCB) is a standard circuit breaker with an additional differential function.
The standard thermal magnetic circuit breaker mainly protects equipment and circuits. It monitors the current intensity and intervenes in the event of an overload or short circuit. It is the basic protection for all electrical circuits.
The differential function, found in residual current circuit breakers, detects current leaks. It compares what enters and leaves the circuit. Any difference signals a potentially dangerous problem for people (such as accidental contact with a bare wire). The circuit breaker then cuts off the power supply to prevent the risk of electrocution.
To put it simply:
- The magnetic thermal component protects your electrical equipment
- The residual current device protects people from electric shocks
- A standard installation always combines these two types of protection for optimum safety.
A standard installation always combines these two types of protection for optimum safety.
How to choose the right thermal circuit breaker?
To choose the right circuit breaker, consider the type of circuit that needs to be protected and its specific characteristics.
First, consider the issue of nominal intensity. This is the maximum current that the circuit can handle:
- 10A for lighting circuits
- 16A for standard electrical outlets
- 20A or 32A for large appliances
The number of poles depends on your installation:
- 1P+N (1 pole protected) for all domestic circuits
- Bipolar for specific circuits
- Three-pole or four-pole for three-phase installations
The operating voltage must correspond to your mains supply:
- 230V for standard domestic installations
- 400V for three-phase applications
An undersized circuit breaker trips too often. An oversized circuit breaker will not protect your installation properly. A well-chosen circuit breaker guarantees effective protection and contributes to the longevity of your equipment while ensuring optimal safety.
The different trip curves of the thermal magnetic circuit breaker
From curve B (very sensitive) to curve D (less sensitive), including the specific curves K, MA and Z, choosing the right trip curve for your circuit breaker is essential to adapt your protection to the specific characteristics of your equipment.
The case of thermal magnetic motor circuit breakers
Thermal magnetic motor circuit breakers are specifically designed to protect electric motors. They are essential equipment for industry (where motors are subject to very demanding operating conditions). Thanks to them, unexpected shutdowns and risks associated with electrical malfunctions are a thing of the past!
Their main advantage? These motor circuit breakers can be used as control switches to manually start and stop motors.
Discover Schneider Electric's TeSys GV2 range, specially designed for protecting and controlling electric motors, available from stock at One-Elec!
Electrical connections for the thermal magnetic circuit breaker
The installation of a thermal magnetic circuit breaker must follow specific rules to ensure its effectiveness. The connection must respect the direction of current flow in order to function correctly. Caution: this work must be carried out by a qualified professional.
The connection is usually made on a DIN rail in the electrical panel. The input of the circuit breaker receives power from the mains or the main circuit breaker. The output is connected to the circuit to be protected according to a standard diagram.
In a standard single-phase circuit, the phase is protected by the circuit breaker, while the neutral passes through and is not protected (not switched) by the circuit breaker. For installations requiring neutral protection, a double-pole circuit breaker is required. The earth conductor never passes through the thermal magnetic circuit breaker and is directly connected to the earth terminal block.
It is essential to observe the cable cross-sections when connecting. An undersized conductor may overheat even with a suitable circuit breaker. The connection must be closed to prevent overheating at the terminals.
For safety reasons, installation must always be carried out with the power disconnected. A manual test should then be carried out to check that the device is working properly.
Need a reliable thermal magnetic circuit breaker for your installation? One-Elec offers a comprehensive range of circuit breakers that comply with all relevant standards. Fast delivery guaranteed on all items in stock.
