The function and working principle, technical parameters and selection of RCCB/ELCB

(1) Function: It is mainly used to quickly cut off the power supply when a personal electric shock or leakage occurs, to ensure personal safety and prevent electric shock accidents. Some RCCB/ELCBs also have overload and short circuit protection, which are used to start and stop the motor infrequently.

(2) Working principle: When working normally, no matter whether the three-phase load is balanced or not, the sum of the three-phase current phasor passing through the main circuit of the zero sequence current transformer is equal to zero, so there is no induced electromotive force in the secondary winding, and the RCCB/ELCB Work in a closed state. If an electric leakage or electric shock accident occurs, the sum of the three-phase current is no longer equal to zero, but equal to a certain current value Is. Is will form a loop through the human body, the earth, and the neutral point of the transformer, so that the secondary side of the zero-sequence current transformer generates an induced electromotive force corresponding to Is, which is added to the trip unit. When Is reaches a certain value, the trip unit will act. Push the lock of the main switch to disconnect the main circuit.

(3) Parameters and types

Parameters: rated current, rated leakage operating current, rated leakage operating time.

Type: According to the action mode, it can be divided into voltage action type and current action type; according to the action mechanism, there are switch type and relay type; according to the number of poles and lines, there are unipolar two-wire, two-pole, two-pole three-wire, etc.

(4) Selection: The RCCB/ELCB should be selected according to the purpose of use and operating conditions:

Choose according to the purpose of use:

①For the purpose of preventing personal electric shock. Installed at the end of the line, select a high-sensitivity, fast-type RCCB/ELCB.

② For branch circuits that are used together with equipment grounding for the purpose of preventing electric shock, select medium sensitivity and fast RCCB/ELCBs.

③The main line used to prevent fire caused by leakage and to protect lines and equipment should use medium sensitivity and time delay type RCCB/ELCB.

According to the power supply mode:

① When protecting single-phase lines (equipment), use single-pole two-wire or two-pole RCCB/ELCBs.

②When protecting three-phase lines (equipment), choose three-pole products.

③When there are both three-phase and single-phase, choose three-pole four-wire or four-pole products.

5) How to use

① When selecting the number of poles of the RCCB/ELCB, it must be compatible with the number of lines to be protected.

②Check the leakage reliability after installing the watt-hour meter and the fuse, and check it regularly.