15-10-20

Knowledge blog: circuit breakers

Kennisblog Our engineering manager John Meijer shares his knowledge. Every month, he discusses a different topic in the field of electrical safety. This time his blog is about: circuit breakers.

Application: domestic or industrial

The IEC 60898-1 is related to circuit breakers for domestic installations. This norm applies for homes, schools and shops, among other things. These circuit breakers are available with a short-circuit breaking capacity of 4.5 KA to 25 KA at 230/400 VAC.

The IEC / EN60947-2 is related to circuit breakers (MCBs, MCCBs, ACBs) for industrial installations. These circuit breakers protect the electrical installation up to 1,000 VAC and 1,500 VDC with a variety of versions between 0.2 A and 6,300 A.

This means that during the design of an installation, it is necessary to look carefully where the circuit breakers will be used. Depending on the choice, a kA value must therefore be chosen according to the IEC 60898-1 or the IEC / EN60947-2. In case of possible operation by people in shops, homes, schools etc., the IEC 60898-1 must always be applied.

Misunderstanding about C circuit breakers

For example, a circuit breaker with C characteristic can hardly ever be used in a 24V circuit. Some 24V power supply suppliers say that the power supply peaks ~ 5x In for 12 mS to trip the circuit breaker.

By means of a test in practice, we have shown that a C circuit breaker cannot be used at low voltages, because it simply does not switch off. See video.

More information?

The following topics were also discussed during John Meijer’s training sessions:

  • When to use a 2P circuit breaker and when to use a 1P + N circuit breaker?
  • What characteristics are there and when do you apply which?
  • What is the difference between a DC and AC circuit breaker?
  • What should be the maximum switch-off time and how do I determine it?
  • Why do certain circuit breakers not work in a 24V circuit?

If you have any questions about the above points, we can advise you.