Industry Dynamic

Troubleshooting method for terminal failure of molded case circuit breaker and contactor


The molded case circuit breaker can automatically cut off the current after the current exceeds the trip setting. Molded case refers to the use of plastic insulators as the casing of the device to isolate conductors and grounded metal parts. Molded case circuit breakers typically contain thermal magnetic trip units, while larger models have solid state trip sensors. The trip unit is divided into: thermal magnetic trip and electronic trip. Commonly used, the rated current has the following types: 15 25 30 40 50 60 75 80 100 125 160 200 225 250 315 350 400 500 630 A.

Contactors are divided into AC contactors (voltage AC) and DC contactors (voltage DC), which are used in electric power, power distribution and consumption. In a broad sense, a contactor refers to an electrical appliance that uses a coil to flow through a current to generate a magnetic field to close the contacts in industrial electricity to control the load.

Before we are ready to wire the product, we must first choose the appropriate lead wire, first use a single-strand copper wire, if there is no single-strand copper wire, use multi-strand annealed copper wire, then we only have to solder the wire ends together with tin to form Single strand.

If the conditions do not permit, then we try to twist the multi-strand wires into one strand, leaving 4-5 strands to twist other soft wires into one, or use terminal lugs for wiring. It is recommended to use round and U-shaped terminal lugs. A single lug is recommended.

The reason for this is to prevent phase-to-phase short circuit or ground short circuit caused by exposure of multiple copper wires.

When wiring, we try to make the wire ends into n-shaped. Why do we make n-shaped? Because we generally use crimping for small circuit breakers or molded case circuit breakers and AC contactors, that is, nut crimping. line, such as: miniature circuit breaker.

They all use crimping frame wiring. If we use single-strand 1-shaped wiring, it is easy to cause changes in the internal structure of the product. For example, most air switches use wiring frame crimping. If 1-shaped wiring is used Wiring, it is easy to cause the internal contacts to slip, because it is impossible for us to press the wire in the middle of the wire frame when we press the wire. If it is pressed next to the wire frame, it will be caused when we tighten the screws.

The static contact is displaced, causing the air switch (miniature circuit breaker) to be in poor contact or to be in contact. If we make the copper wire into an n-type, it doesn’t matter whether you place it in the middle or next to it, because it has a large contact area and it is easy to find a flat point.

When tightening the screws, the internal structure of the product will not be damaged.

The contactors all use screw caps to press the wires. Most of the screw presses of the AC contactor are ∧-shaped. When the screw is screwed down, the ∧-shaped will slowly press down the lead wire. If the 1-shaped The common use of a single wire will also cause unbalanced screws. When we tighten the screws hard, it is easy to cause the internal contacts to tilt to one side, resulting in no electricity and contact between the contacts. Whether we use multi-strand wires or single-strand wires The n-shaped wire head is used to connect the product, which will make the product have a balance point when wiring, and the wiring will not be tight, so as to reduce the failure rate.