Malfunctions of circuit breakers, their causes and remedies

Modern circuit breakers are not intended for repair because they are supplied in a non-separable housing. The manufacturer intends to replace them, at the same time, domestic-made AP type machines were not supposed to only disassembly, but adjustment, with a certain skill, you could assemble from several faulty one completely worker. From the article you will learn what are the malfunctions of circuit breakers and how to fix them. The machines under consideration are used in electrical circuits with voltages up to 1000 V, to protect risers and supply lines.

How the protection apparatus works

To understand the causes of all malfunctions, you need to consider the device of the machine. It consists of a pair of power contacts, a thermal disconnector and an electromagnetic disconnector.

The thermal disconnector trips slowly, with a slight (up to 2 or more times, depending on the time-current characteristics of a particular circuit breaker), exceeding the rated current. Electromagnetic - in case of a short circuit or exceeding the current several times, it is triggered in a fraction of a second. At first glance, it may seem that there is nothing to break here, but let's consider each of the mentioned malfunctions separately.

The main problems with machines

The machine has only three main faults:

1. Knocks out.
2. Doesn't turn off.
3. Not cocked.

The machine knocks out - this means that either suddenly, for no apparent reason, the voltage disappears, or when the load is switched on to one of the circuits, the power supply is disconnected. The machine can also not turn on in different ways:

• When the lever is cocked, it immediately goes down, the voltage appears for a short time or does not appear at all.
• The lever is jammed and does not cocked at all and does not work.
• If you hear a burning smell or the wires from the circuit breaker have burnt out, you must turn it off before start repairs, but the lever simply does not budge, as described in the previous paragraph, only in the included position.

The machine knocks out for no apparent reason

Periodic knocking out of the circuit breaker is associated with the operation of the thermal disconnector or power surges in the mains supply. With the latter reason, you cannot do anything, except to put a voltage stabilizer at the input to the machine, but this is expensive. But the shutdown on the thermal disconnector is associated with a long, but insignificant in magnitude, excess of the rated current.

More often than not, this is not a malfunction of the circuit breaker, but rather improper use of it. First of all, you should find out what current it is designed for, it is written on the front panel. Then calculate the total current consumption of electrical appliances that are powered through it. If the current is not indicated on the devices, the power consumption should appear on them, in this case, divide the number of W by 220 V, then you will find out the number of Amperes through the machine.

If the result obtained exceeds the rating of the machine, it will open. If the machine hums or rattles, this is a sign of its overload.

Solution: Reduce power line consumption, turn on powerful devices in turn.

If the rating of the circuit breaker is selected correctly, the point is different. The thermal disconnector is for that thermal, in order to open when overheating, and the source of heat can be burnt power contacts (as in the photo below) or wires not tightened in the terminal blocks. Both of these lead to an increase in contact resistance, and heating, since the case is closed, the heat has nowhere to go, the thermal protection plate gradually heats up, over time it will open.

Solution: Check the tightness of the wire, remove it, if necessary, clean it from oxidation and carbon deposits, and then tighten it again. The contacts cannot be cleaned without disassembling the machine; it is better not to “treat” this malfunction, but to replace the circuit breaker. To disassemble it, you can drill rivets and open the case, but you run the risk of not assembling it or assembling it with errors, skewed and mechanical defects, which will make it difficult to work correctly.

Overheating can also occur from heat sources located next to the AV in the shield itself. Check the temperature of the surrounding devices with your hand, perhaps something is heating up nearby.

Triggering when the load is switched on

If a malfunction occurs when some of the circuits are turned on, for example, a light, the malfunction is probably in the lamp or the wiring leading to it. Due to the violation of the integrity of the insulation of the cable or connections, short circuit.

Solution: Diagnostics and repair consists in disconnecting the main line cable and replacing it with a temporary one, if it helped, then you have to revise and repair the wiring.

Instantaneous shutdown of the machine is associated with the operation of electromagnetic protection. It does not lock in the on position due to internal problems with the same electromagnetic shielding. You can check the serviceability of the machine by replacing it with a knowingly serviceable one, with the same rated current and sensitivity - if everything worked properly, the reason is in it. If the circuit breaker does not charge without voltage, and there is no short circuit, it needs to be replaced.

Circuit breaker does not turn on

If you lift the lever up, but the circuit breaker does not turn on, and the lever instantly falls down, this is due to either mechanical wear of the machine's components or the presence of a short circuit. You can check this by ringing the supply phase to zero with a low-resistance continuity, for example, a control lamp, or an ohmmeter. High-resistance continuity (for example, LED control) can mislead you and the circuit can ring through the load (light bulbs, heating elements or electric motors). If the circuit is closed, then there is a breakdown of the cable insulation.

Solution: Eliminate the malfunction by replacing the cable or restoring the insulation. If there is no short circuit, then the machine is replaced.

Lever is stuck

Another thing is when you cannot move the machine lever from the lower position, which means that the contact drive mechanism is jammed. This malfunction can occur when disconnected under load, if a strong arc has arisen and its splashes have jammed the moving contact, or rather its assemblies, or it is soldered into the case.

Solution: Grab the lever closer to the base and pull it up strongly, but smoothly, and there is a chance of breaking it off. In the future, you will not be able to use such a machine. It is still likely to jam in the future, then the machine should be replaced. The success rate in this procedure is 50%, in practice the lever often breaks off, especially if it happens in the cold.

The machine does not turn off when there is a short circuit

There can be two reasons for the lack of response to short circuit. First, the contacts are stuck. Due to heating and arcing during openings, the contacts adhered to each other. The second - the mechanism of the electromagnetic disconnector is jammed.

Solution: If the machine does not work in case of short circuits, try to break the contacts with effort, if it does not work, then replace the machine.

How to extend the life of a circuit breaker

Remember two tips:

• Do not overload the protected line with a current higher than the rated one.
• Do not switch off the machine under load.

While everything is clear with the first tip, the second is a little more complicated. When current flows through the contacts and you are about to disconnect them, an arc occurs. This is due to the truth of the laws of commutation: "The current in the inductor cannot stop instantly."

Even if the load is active, for example a heater, the cables have their own parasitic inductance. It is even more dangerous to open a circuit breaker if a load such as electric motors is connected to it. or lighting networks with a large number of chokes (DRL, DNat, LL) - the inductance is even greater, the arc too. Hence, contact defects, their carbonization, accelerated wear and sticking.

We got acquainted with the defect caused by what. The circuit breakers will last quite a long time if they are operated within the rated conditions. Modern machines cannot be repaired, so we do not recommend disassembling them, it is better to replace them with a quality analogue, for example, Moeller or ABB. For household appliances and active loads, use machines with the letter B, to connect loads with significant with starting currents (motor), devices with the letter D are better suited, and the number after the letter indicates the value of the permissible current. Do not connect oxidized wires and always tighten the terminals. Adhering to these tips, malfunctions of circuit breakers will occur much less often, and you will not have to worry about the safety of operating the wiring in an apartment or house.

Finally, we recommend watching a useful video on the topic:

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