Basic principle of residual current action protector - News - Global IC Trade Starts Here Free Products

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

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Although there are many types of residual current action protectors, the basic principle is basically the same. Generally, the abnormal unbalanced current appearing on the line is used as the action signal. The basic principle of the armature breaking residual current action protector in the direct mode is illustrated as an example. Figure 4-7 shows the circuit diagram of the switch. The zero-sequence current transformer on the left side of the figure is used for detecting signals. The magnetic field generated in the iron core through the three-phase power supply wire of the transformer cancels each other, and the induced potential is not generated in the secondary side H of the transformer, and there is no current. The suction of the polarized electromagnet T on the right side of the figure overcomes the reaction. The tension of the spring keeps the armature in the closed position and the line switch does not move. When the equipment leaks, the zero-sequence current (the sum of the three-phase current imbalance) occurs in the three-phase power supply line through the transformer, the induced electromotive force is generated in the secondary side of the transformer, and the current flows through the polarized electromagnet coil. And generating an alternating magnetic flux, the magnetic flux is superimposed on the magnetic flux of the permanent magnet, and the result of the food addition is that the electromagnet is demagnetized, so that the suction force of the armature is reduced, and the armature is pulled apart by the reaction force of the spring. The trip mechanism TK operates and the power is turned off by the switch device.

Residual current operated protectors with zero-sequence current transformers can be used for neutral point grounding systems as well as neutral point ungrounded systems. In a three-phase four-wire system, if the device is protected with zero at the same time, the neutral wire should not be used as the primary side of the transformer, so that the transformer can reflect the zero-sequence current caused by leakage. However, if the switch is used for a small-capacity current line, the unbalanced single-phase load may be present on the line. The neutral line should be used as the primary side of the transformer together with the three phase lines. Otherwise, the leakage switch will operate as long as the load is unbalanced.

The residual current action protector should normally be mounted on the branch circuit. When several devices are grounded by a common grounding wire, in order to prevent the occurrence of accidents, each branch circuit connected to these devices must be separately installed with a leakage switch.

The residual current action protector should be tested with the test button on the protector before use. After the residual current action protector is in use, the electrician should promptly find out the cause of the action. Do not vote again before the fault is eliminated. After the fault is removed, the residual current action protector must be tested again using the test button before it is put into operation again.