Sep 28, 2017
Cake Cooler leakage protector
Leakage protector (leakage protection switch) is an electrical safety device. The leakage protection device installed in the low-voltage circuit, when the leakage and electric shock occurs, and reached the protection of the action of the current limit, it will immediately within a limited time action automatically disconnect the power supply for protection. As the electrical equipment, because the need for refrigeration system work, so the use of power is essential, leakage protection device has become an essential equipment for the cake cabinet.
Leakage protector is mainly composed of three parts: detection components, intermediate amplification, operation of the implementing agencies. ① detection components. By the zero sequence transformer, the detection of leakage current, and send a signal. ② amplification link. Will be weak leakage signal amplification, according to the device different (amplification components can be used mechanical devices or electronic devices), constitute an electromagnetic protector phase electronic protection. ③ executive body. Upon receipt of the signal, the main switch from the closed position to switch to the open position, thus cut off the power supply, is the protection circuit out of the grid trip parts.
① when the electrical equipment leakage occurs, there are two anomalies: First, the three-phase current balance was destroyed, there is zero sequence current; Second, the normal non-charged metal shell to ground voltage (normal, metal Both the shell and the earth are zero potential).
② the role of zero sequence current transformer leakage protection device through the current transformer to detect abnormal signals, through the intermediate mechanism conversion transfer, so that the actuator action, through the switch device to disconnect the power. The structure of the current transformer is similar to that of a transformer, and is composed of two coils that are insulated from each other on the same core. When a coil has a residual current, the secondary coil will sense the current.
③ working principle of leakage protector will be installed in the circuit leakage protection, a coil and the grid connected to the line, the secondary coil and leakage protector in the release. When the electrical equipment is running normally, the current in the line is balanced, the sum of the current vectors in the transformer is zero (the current is the direction vector, such as the direction of the outflow is "+" and the return direction is "-" Transformer reciprocating current in the same size, the opposite direction, positive and negative offset each other). Since there is no residual current in the primary coil, the secondary coil is not induced, and the switching device of the leakage protector is in the closed state. When the equipment shell leakage and someone touched, then the fault point in the shunt, the leakage current through the human body to work ground, return to the transformer neutral point (not the current transformer), resulting in the transformer into the flow, Current imbalance (current vector sum is not zero), a coil to produce residual current. Therefore, it will sense the secondary coil, when the current value to the leakage protection device to limit the operating current value, the automatic switch trip, cut off the power.