Function of Molded Case Circuit Breaker Accessories
As a derivation and supplement of circuit breaker function, accessories add control means and expand protection function for circuit breaker. They are an indivisible and important part of circuit breaker. They mainly include auxiliary contacts, alarm contacts, shunt trippers, under-voltage trippers, electric operating mechanism, external rotating operating handle and other accessories.
1) Auxiliary contacts are mainly used to display the breaking and closing status of circuit breakers, but can not show whether the breaking is broken. They are connected to the control circuit of the circuit breaker. The rated current of shell-frame grade of plastic-shell circuit breaker is 100 single breaking point conversion contacts, 225 and above are bridge-type contacts, which stipulate heating current 3A; the rated current of shell-frame grade 400 and above can be installed two. Normally open and two normally closed, the agreed heating current is 6A.
2) The alarm contacts are mainly used for freely tripping when overload, short circuit or under-voltage faults occur in the load of the circuit breaker. The working currents of the alarm contacts are AC380V, 0.3A, DC220V and 0.15A, which generally do not exceed 1A, while the heating current can range from 1 to 2.5A.
3) Excitation tripper is an accessory for long-distance operation of switch-off. Its voltage can be independent of the main circuit voltage. Excitation tripper is a short-term working system. The coil power-on time can not exceed 1 s, otherwise the coil will burn out. In order to prevent the coil from burning out, a micro-switch is connected in series with the coil of the shunt tripper. When the shunt tripper is electrified, the armature is sucked, and the micro-switch is changed from normal closed state to normal open state. Because the control circuit of the power supply of the shunt tripper is cut off, even if the button is pressed artificially, the shunt coil will never be electrified. It avoids the coil burning, and when the circuit breaker re-closes, the micro-switch is in the normal closed position again. There are many kinds of control voltages and different power supply frequencies for different occasions and different power supply choices.
4) Undervoltage tripper is used as long-term voltage protection for lines and power supply equipment. When used, the coil of undervoltage tripper is connected to the power side of the circuit breaker. Undervoltage tripper can be closed only after the circuit breaker is electrified, otherwise the circuit breaker will not close. Users should confirm whether the operating voltage of the line and the undervoltage tripper is the same. The operating range of undervoltage is (70%-35%) Un. Undervoltage tripper also has a variety of rated working voltage and different power supply frequencies, which can be used in different occasions and different power supply.
5) Electric operating mechanism is used for automatic control of circuit breaker and long-distance closure and disconnection. There are two kinds of electric and electromagnetic operating mechanisms: electric operating mechanism is driven by motor, which is generally suitable for circuit breakers with rated current of 400 A or more in shell level, and electromagnetic operating mechanism is suitable for circuit breakers with rated current of 225A or less in shell level.
Flying Arc Distance
When a circuit breaker breaks a large short-circuit current, its dynamic and static contacts separate to produce arcs. Some arcs or ionized gases are ejected from the arc nozzle at the power supply end of the circuit breaker. The arc itself is a huge current, which easily leads to the bare conductor and the bare charged body and the "ground" (the metal shell of the complete set of equipment is). Grounded) Interphase Short Circuit and Ground Short Circuit Accidents. In order to ensure safety, users should leave a certain distance according to the product samples or data provided by the manufacturer's instructions. If the height distance of distribution box and cabinet is insufficient, the products with small or zero flying arc distance can be selected to ensure the safety of power consumption.
