What is a differential switch?

What is a differential switch?

The differential switch or also known as a differential circuit breaker, is an electromechanical protection device, which is mainly used to prevent people from suffering any type of electric shock caused by a current leak.

A current leak originates when a part of the current escapes from the system and goes to a physical earth (it is called physical earth because it literally goes to earth). This can occur when a bad or poorly connected cable contacts a conductive surface and a person or grounding object arrives.

How does a differential switch work?

This device is in charge of monitoring the input current with the output current at all times and when a difference is detected that exceeds that established by the type of switch (usually 30mA), it trips to open the circuit and thus protect the person from a possible accident.

Monitoring is achieved by placing two coils in opposite directions so that the magnetic fluxes that are created are canceled, but if for some reason more current passes through one of the coils, it generates a greater flux that causes a small current in the monitoring coil. This current is sufficient to activate an electromagnet that opens the switch contacts.

Differential switch parts

Although it may be thought that this is a very complicated device, it is not, since it has very few essential parts such as;

• Toroidal core: It is a donut-shaped object with magnetic properties where the coils are placed.
• Coils: Three wires are used that are wound on the toroidal core, one for the phase, one for the neutral and the last for the cutting system.
• Cutting system: An electromagnet is used that manages to open the circuit when the current difference is generated.
• Test Button: This button practically simulates a current leak through an electrical resistance .

Types of differential switches

Because leakage currents can arise in various ways, there are different classes and types of differentials, each meeting different goals.

Differential classes

The classes of a differential are based on performance, the types of signals they process;

• Ac: They are common in domestic installations and are used for leaks with sinusoidal signals
• A: They detect leakage current with sine wave and half wave or pulsating.
• F: They are used for sinusoidal and half-wave or pulsating signals with a signal of up to 1KHz
• B: They are practically the most complete since they work with sine, pulsating and direct current waves.

Differential switches according to your sensitivity

We can find differentials of all the previous classes but with more or less leakage current;

• 6 and 10 mA: These are used to prevent leakage mainly in humid environments
• 30 mA: They are those used to protect people from electric shocks
• 300 and 500 mA: They serve to prevent fires