Circuit breaker of the upper and lower in-coming wires
In the above article, we speak of a circuit breaker wiring way and kind, the article also mentioned the breaker 's upper and lower in-coming wires on the circuit breaker will have effect. In this paper detailed discuss. On line and the lower line up. What is the upper line and the lower into the thread?
Progress line shows that the power is connected in the circuit breaker cover plate marked with the LINE or 1, 3, 5, 7 on one end ( MCCB handle" ON" (" and" ) above ), load connected in circuit breaker plate marked with the LOAD or 2, 4, 6, 8 on one end ( plastic shell type circuit breaker handle" OFF" (" points" ) below. ). The line is a direction, power line connected with the LOAD, LINE load line. For the vast majority of the plastic shell type circuit breaker, such as DZ20 molded case circuit breaker series can only progress line but not in line. Universal type circuit breaker DW15-630, DW16-630 could only progress line. DW16-2000, DW16-4000 specifications can progress lines, can also be in the line. DW40, DW45 various current can be motivated line may also be in the line.
On line and not only motivated by the line of reasoning is:
1) structure: the plastic shell type circuit breaker, motivated line power line through the connecting plate - static contact dynamic contact - - soft connection - protection system ( bimetallic element or the heating resistance element and an electromagnet system ) - connecting plate; and the lower inlet line is power line - connecting plate - protective system soft connection - - static contact dynamic contact connection plate. Next in line, if breaking short circuit current, arc although most into the arc-extinguishing chamber, but there are some live free gas to the movable contact connecting part of the mobile phase, the free gas and adjacent the charged body contact, can occur in interphase short circuit. On the other hand, circuit breaker even succeeded in breaking short circuit current, but because it is the lower wiring, protection system, soft connections, public shaft has been in the power supply voltage ( although no current flows ), will make the pieces of insulation aging, may also produce interphase creepage accidents.
2) the recovery voltage of reason: the so-called recovery voltage refers to the circuit breaker with short circuit process, in a dynamic and static contact between the voltage. As long as the arc through the elongated and drive into the arc-extinguishing chamber, so that the cooling, improve the arc and the arc voltage and the arc resistance, voltage is greater than the recovery voltage, arc can be extinguished. Recovery voltage has a steady state recovery voltage and transient recovery voltage two. Transient recovery voltage of two important parameter is the oscillation frequency of F and oscillating coefficients R, F and R, contact voltage increase rate is higher also, extinction of the arc is more difficult. While the oscillation frequency! And line inductance, capacitance and resistance has the very big relations. In line for a string of components, inductors, capacitors. Resistance to upward line is much higher ( progress line is only through the connecting plate and the static contact ), so its transient recovery voltage is much higher, extinguishes the arc very difficult, often cause breakdown arc reignition.
DW16 DW15, the current specification (1600A ) and DW40, DW45 is not only can progress line to line is because: contact opening distance ( dynamic and static contacts disconnected distance ) is larger, distance and take some isolation and increase the insulating measure, DW40, DW45 each phase with plastic structure isolation or formation of a solution, may lead to phase short circuit and the problem of transient recovery voltage. Some MCCB, due to the adoption of the double breakpoint or short-circuit breaking capacity have great margin, so can be both motivated and lower inlet line line.
Reverse ( in line ), may also cause an electric shock hazard. Because the average person according to the habit, think that the upper end of the handle ( ON ) is connected to the power supply, the lower end is connected with the load ( OFF). Although the circuit breaker is opening, but if there is no understanding of the situation that load end no voltage, to touch, it may get a shock ( reverse load terminal voltage ).
It is necessary to mention with overload, short circuit protection of the electronic type residual current operated circuit breaker ( earth leakage circuit breaker ) connection, they can only progress line. This is because the electronic type residual current operated circuit breaker tripping coil is mounted in close proximity to the load side, upper line, release coil in when leakage occurs, it makes the tripping of the circuit breaker, because the moving and static contacts open, movable contacts is no voltage; if it to next line, leakage after operation, circuit breaker opening, from the original load end ( by line load end became the power end ), to release coil and a moving contact is provided with voltage, if the line voltage surge phenomenon of fault, will burn coil, so that the residual current operated circuit breaker lost due function.
The above information by the country electric switch factory, reference materials ( www.jiandq.com )