The upper LINE indicates that the power supply is connected to one end of the circuit breaker cover marked with LINE or 1, 3,5, 7, above the handle of the molded case circuit breaker "ON" (" close ");
The LOAD is connected to one end of the circuit breaker cover marked LOAD or 2.4, 6,8, below the "OFF" (" cent ") of the molded circuit breaker handle.
The next LINE is inverted in a direction, the power LINE LOAD, LOAD LINE, for the vast majority of plastic shell type circuit breaker, can only be on the LINE and not down the LINE. Some of the universal circuit breaker can only be driven line.
Some specifications can not only aspirant line, but also under the line. Even some specifications all kinds of current can be aspirant line can also be under the line.
Come to understand first, can aspirant line and the reason that cannot enter line below.
Structural reasons: for molded case electrical equipment circuit breaker, the upper line represents the power line through the connecting plate - static contact - moving contact - soft connection - protection system - connecting plate; The incoming line is the power line - connecting plate - protection system - soft connection - moving contact - static contact connecting plate. Under the line, if the short circuit current is cut off, although most of the arc into the arc extinguishing chamber, but there is always a part of the free gas charged to the moving contact connection part of the free gas phase and the adjacent phase charged body contact, phase short circuit may occur.
On the other hand, even if the circuit breaker successfully breaks the short circuit current, but because it is the wiring, the protection system, soft connection, the common rotating shaft has been under the power supply voltage, will make the insulation aging, may also produce phase creepage and other accidents.
The reason for restoring voltage: the so-called restoring voltage refers to the process of the circuit breaker breaking the short circuit, and the voltage added between the dynamic and static contacts. As long as the arc is elongated and driven into the arc extinguishing chamber, so that it is cooled, improve the arc resistance and arc voltage, and the arc voltage is greater than the recovery voltage, the arc can be extinguished.
The recovery voltage is divided into steady-state recovery voltage and transient recovery voltage. The two important parameters of transient recovery voltage are oscillation frequency and over-oscillation coefficient, and the larger and, the higher the voltage increase rate between contacts is, the more difficult it is to quench the arc. And the oscillation frequency! It has a great relationship with the inductance, capacitance and resistance of the line. Down the line because there is a large string of components, inductance, capacitance. The resistance is much higher than the upper line, so its transient recovery voltage is much higher, it is very difficult to extinguish the arc, often cause breakdown and arc reburning.
Some of the large current specifications can be both the upper line and the next line because of the contact open distance is larger, and take some isolation and increase insulation measures, each phase with plastic structure isolation or the formation of an independent chamber, to solve the problem that may lead to short circuit and transient voltage recovery.
Some molded case Circuit Breaker, because of the use of double breakpoints or short circuit breaking capacity has a great margin, so it can both the upper line and the next line. Reverse connection (down into the line), but also may cause electric shock danger.
Because general people according to the habit, always think that the upper end of the handle (ON) is connected to the power supply, the lower end (OFF) is connected to the load.
Although the electrical equipment circuit breaker is split, but if a person who does not know the situation thinks that the load end of the power voltage, to touch, may be shocked. It is necessary to mention the wiring of electronic residual current action circuit breakers (leakage circuit breakers) with overload and short circuit protection, they can only be on the top line.
This is because the tripping coil of the electronic residual current action circuit breaker is installed near the load side, the upper line, tripping device coil in the leakage, it makes the circuit breaker trip, because the dynamic and static contact is open, there is no voltage at the moving contact;
If now into the line, leakage action, circuit breaker break, from the original load end (because of the load end into the line into the power end), to tripping coil and moving contact are voltage, if the line voltage surge phenomenon and other faults, will burn the coil, so that the rest of the current action circuit breaker lost its due function.
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