What is a DC circuit breaker ?

    The DC circuit breaker is a circuit breaker used for the operation mode conversion or fault removal of the DC system. It is used for overload and short-circuit protection of the facilities and electrical of the DC power distribution system. It can be widely used in electric power, post and telecommunications, transportation, industrial and mining enterprises and other industries.

The working principle of DC circuit breaker:

    The main circuit of the circuit breaker consists of a lower connecting row supporting moving contacts, an upper connecting row and silver-plated contacts. The closing device is composed of a large pot-shaped magnet with a closing coil. The magnet contains a moving magnetic core, a contact pressure spring and a magnetic core return spring; all these components are mounted on the operating rod. The fork unit is installed on the top of the operating rod. The overcurrent trip device includes an armature made of laminated sheets, and a moving magnetic core connected to an operating rod controlled by a spring. The trip setting value can be set due to the action of the rod. The five pairs of auxiliary contacts are all reversing contacts controlled by moving contacts. They are located in a plastic box at the bottom of the closing device. The arc extinguishing chamber includes a corner plate, a partition plate and a deionizing plate, all of which are installed between the two arc extinguishing plates. When the circuit breaker is opened due to overcurrent or a normal opening command, the propulsion mechanism will drive the moving contact to open. The propulsion mechanism also acts on 5 reversing auxiliary contacts

DC circuit breaker type:

1. Two-stage DC circuit breaker. The two-stage DC circuit breaker operates correctly and cooperates well when the short-circuit current is 8-10 times the rated current of the upper switch, and with a difference of 4 to 5 levels.

2. Three-section DC circuit breaker. Three-stage DC circuit breaker, when the upper stage is three-stage, and the lower stage is two-stage or three-stage DC circuit breaker, the level difference is 2, and the short-circuit current is 25-40 times the rated current of the upper-stage circuit breaker. .

Wiring of DC circuit breaker:

1. Wiring behind the board. The advantage of the wiring behind the board is that when maintaining the DC circuit breaker, you only need to disconnect the front-level power supply without rewiring. This kind of structure is relatively special, and they are equipped with special installation plates and screws. When installing, they must be installed in strict accordance with the manufacturer's requirements to avoid affecting the normal use of the circuit breaker.

2. Plug-in wiring. The advantage of plug-in wiring is that when the circuit breaker needs to be replaced, just pull out the old circuit breaker and replace it with a new one. The operation is faster and more convenient than the front and back wiring of the board. When using this method to install, ensure that the plug is securely fastened, so as to reduce contact resistance and improve safety and reliability.

3. Drawer type wiring. The in and out drawers of products such as DC circuit breakers are realized by the clockwise or counterclockwise rotation of the rocker, and the plug-in structure is adopted on the main and secondary circuits.

Selection method of DC circuit breaker:

According to the selection of the DC circuit: Whether the DC circuit is operating normally is the most basic way to select the DC circuit breaker. It is necessary to ensure that the DC circuit breaker can carry normal load current.

Choose according to the rated voltage and grounding method of the DC power supply: The selection of the rated voltage and grounding method of the DC power supply is divided into three methods: negative grounding, center point grounding, and neither positive nor negative grounding.

. Negative grounding: The most important method of negative grounding is the insulation isolation of the negative pole. Therefore, it is necessary to add 1 pole to the negative pole of the circuit breaker in terms of insulation isolation.

. Center grounding: The most important way of center grounding is to determine the number of poles of the circuit breaker for the positive and negative poles. Therefore, it is necessary to connect the circuit breaker in series with both the positive and negative poles.

. The positive and negative poles are not grounded: the positive and negative poles are not grounded. The most important thing is to determine the number of poles of the circuit breaker required, so the short circuit needs to be broken.

The difference between DC circuit breaker and AC circuit breake:

 The main difference between a DC circuit breaker and an AC circuit breaker is the ability to extinguish arcs. Because the AC has a zero-crossing point in each cycle, it is easy to extinguish the arc at the zero-crossing point, and the DC switch has no zero-crossing point, and the arc extinguishing ability is very poor, so an additional arc extinguishing device must be added. Generally speaking, DC is difficult to extinguish arc, while AC has zero crossing, arc extinguishing is easy