Molded case circuit breakers also termed as MCCB are used with different circuits as a protection circuit. This protection device protects a circuit from overload conditions of current and short circuits. MCCBs are attached with different devices as an additional protection circuit which ensures the protection of a device from fault conditions which can result in damaging the device. MCCBs are considered more accurate than the ACBs due to the use of different technologies in MCCBs. The improvements in the technologies have made the circuit breakers more accurate and précised. The rated current for the MCCB is about 3200 A. The circuit of MCCB is used at the load end due to its compatibility of frequently operating with accuracy. The common accessories for the MCCB include shunt trip, phase insulation barrier, rotary handle, under-voltage tripping device and change over system. The different accessories of the molded case circuit breakers are used to provide more protection. The accessories linked with the MCCB are prewired and the accessories are just attached to the circuits as per the instruction of the manufacturer. The manufacturer of the MCCB accessory defines the groups of the device with which the accessory can work or is compatible. Different common accessories of the MCCB are discussed below:
Phase Insulation Barrier:
The phase insulation barrier is used for safety purposes. This accessory provides the interphase barriers to create appropriate distance between the phases to prevent short-circuiting in the device. If a short circuit between different phases occurs it can cause huge damage to the circuit or a serious personnel injury. Phase insulation barrier is used in different circuit breakers commonly to prevent any kind of incident which can result in a serious injury.
Shunt Trip Device:
The shunt trip is used to disconnect the main power supply to the circuit it is connected within case an electrical signal is received. Whenever a shunt trip device receives a signal from the current transformer it is tripped. When the current is at normal value, the trip is again reset to a normal value and the circuit starts operating. Shunt trip device is triggered once the voltage rises between 70%-110% form the rated coil voltage. These devices are factory fitted with a switch which is the cut-off supply switch.
The plug-in kit for various circuit breakers is used for the ease of plugging in various connections with the circuit breakers. The plug-in kits are supported by some specific circuit breakers which include Compact NSX100, NSX160, NSX250. The plug-in kit is compatible with the Compact NSX circuit breaker and compact NSX DC circuit breakers. There are 3 poles for the plug-in kit. The rated current for this accessory is 250A.
Rotary Handle Function:
The rotary handle function of the MCCB and various circuit breakers allow the user to easily rotate the handle to turn ON or OFF the circuit breaker. The safety device is equipped with the rotary handle to prevent the opening of the panel in case of on condition of the circuit breaker. A bypass screw is also installed for manual intervention in ON state of the breaker. The padlocking facility is also available for various rotary handles. The handle of the breaker can be locked in OFF condition to prevent someone to turn it ON. It provides more safety than the other breakers due to its locking condition.
Auxiliary contacts are used to provide the signal to a device or equipment. The auxiliary contact accessory is used for various circuit breakers. The devices compatible with the auxiliary contact are compact NS630b to 1600, Compact INS, Compact INSE, Compact NR and many more.
Under Voltage Trip Device
This accessory of the circuit breakers is used to cut-off the connection of the circuit from the power supply when the voltage of the circuit drops below the predefined value which is normally 70%. The device is tripped in the same way as it is tripped in the overload conditions. The switch is manually closed in case of the under-voltage trip.