Leakage circuit breaker diagram working principle, parameters, selection and use methods - Database & Sql Blog Articles

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(1) Role: It is mainly used to quickly cut off the power supply when personal electric shock or electric leakage occurs, to ensure personal safety and prevent electric shock. Some leakage protectors also have overload and short circuit protection, which are used to start and stop the motor infrequently.
(2) Working principle: When working normally, regardless of whether the three-phase load is balanced, the sum of the three-phase current phasors passing through the main circuit of the zero-sequence current transformer is equal to zero, so no induced electromotive force is generated in the secondary winding, and the leakage protector Work in a closed state. In the event of a leakage or electric shock, the sum of the three-phase currents is no longer equal to zero and is equal to a certain current value Is. Is will form a loop through the neutral point of the human body, the earth and 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 acts. Push the lock of the main switch to break the main circuit.

(3) Parameters and type parameters: rated current, rated leakage current, rated leakage operation 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 single pole two lines, two poles, two poles and three lines.
(4) Choice: Select the leakage protector according to the purpose of use and according to the operating conditions: according to the purpose of use: 1 to prevent personal electric shock for the purpose. Installed at the end of the line, use a high-sensitivity, fast-type leakage protector. 2 For the purpose of preventing electric shock and grounding the equipment, use a medium-sensitivity, fast-type leakage protector. 3 For the purpose of preventing fires caused by electric leakage and for protecting the lines and equipment, a medium-sensitivity and time-delay type leakage protector should be used. According to the power supply mode: 1 When protecting single-phase lines (equipment), use a single-pole two-wire or two-pole leakage protector. 2 When protecting three-phase lines (equipment), use a three-pole product. 3 When there are three-phase and single-phase, choose three-pole four-wire or four-pole products.
5) Method 1 When selecting the number of poles of the leakage protector, it must be compatible with the number of lines of the protected line. 2 Check the leakage reliability after installing the meter and fuse, and check regularly.