The presence of a developed electrical wiring in a modern property, high power transmitted through it and potential the danger of electrical voltage for humans dictate the need for a number of measures to achieve high security. One of the most effective technical means for solving this problem is the installation of automatic switches that monitor emergency situations and forcibly turn off the damaged section of the network.
Circuit breaker design
A circuit breaker is an electromechanical or electronic switching device that trips when rated current and, by breaking the electrical circuit, protects the wiring and / or the consumer from failure, and the property itself from fire.
Structurally made as a single or multi-pole switching device in a plastic casing with a spark-extinguishing system, Figure 1. There are also elements of indication, control of contacts and connection of wires. Typical installation location is a DIN rail.
Reasons for triggering
The switch breaks the voltage supply circuit to the load in two cases:
- prolonged (for a few seconds or more) excess current by 15-20% of the threshold value - triggered bimetallic thermal splitter that prevents the effects of short circuits shown in Figure 2;
- an abrupt increase in current to two or more of the threshold value - an instant electromagnetic splitter is triggered.
Accordingly, the machine can operate when the threshold current is constantly exceeded and simply when the next device is connected.
Constant excess
Constant excess in normal operation of the electrical system is typical for cases of gradual increase in load. For example, together with the washing machine, an electric kettle is turned on, then an air conditioner, a computer... With this development of events the load is relatively smoothly above the threshold and the switch simply performs its function of protecting the wiring and load.
Eliminate such a triggering is possible only by replacing the element with another one with a higher threshold. At the same time, it is necessary to control the compliance of the operating current and the capabilities of the cables for delivering it to the consumer, for which, first of all, the cross-section of the conductors is checked.
The second case of constant excess is a short circuit in one of the network elements, which is the machine, the load and the wiring itself
Finding the defective item
The simplest way to identify a defective element is the method of sequential switching on of consumers with constant monitoring of the state of the machines.
When implementing a similar procedure, you can use the hierarchical principle of construction of the wiring, which is clearly visible from Figure 3. If, even without full load, the main switch is tripped, the terminal board is additionally monitored. Then the automata of the lower level are sequentially turned on and the defective beam is determined by triggering one of them. Further searches are performed on it.
Abrupt excess
A jump-like excess is characteristic for connecting relatively low-power devices to a network already operating under load. It arises due to the fact that at the moment of switching on the capacitive part of the load resistance is discharged and in the process of going to work modes consumes a large current, which significantly exceeds the threshold, but due to the short duration is not able to cause thermal overheat.
This state of affairs can be corrected by changing the order of inclusion of consumers. The best result, however, is obtained by the distribution of powerful consumers on separate beams.