Elevator Switch Install The Leakage Protection Switch
First of all, it is necessary to explain the principle of leakage protection switch:
Leakage protection switch is to take the leakage action signal, and in a certain leakage conditions cut off the leakage lines, so as not to hurt the body and burn the device device. Leakage protection switch is usually and short circuit, overload and other protective components installed together,Elevator Switch often voltage and current leakage protection switch points. The working principle of the leakage protector is based on the principle of "current balance principle". When the circuit is working normally, the phase current and the neutral current are equal, the sum of the current vectors is equal to zero, and the flux vector and the flux vector in the current transformer core are equal to zero , Then because the current transformer secondary side of the winding signal output,Elevator Switch leakage protection device does not move, the circuit normal power supply. But when the circuit failure or insulation damage leakage, the sum of the current vector is not equal to zero, the current transformer core in the magnetic flux induced by the secondary side of the winding induced voltage, when the fault current reaches a certain value, the induced voltage to leakage protection Release action.
And for the elevator is concerned:
First: the motor can not be started at the start to maintain three-phase current balance, so the sum of the current vector is not equal to zero resulting in leakage protection switch action.
Second: the conversion control of the elevator,Elevator Switch in the start to protect the fan tributary ring, usually using two-phase step-down rectifier way to charge the DC ring, so only two phases at the start of the current, the sum of the current vector is not equal to zero Resulting in leakage protection switch action.
Third: the use of frequency converter,Elevator Switch will produce electromagnetic interference, and in the metal shell after the screen defects, the metal shell will have a potential difference to the ground, so only repeat the grounding the most secure, but repeated grounding, this part of the energy response to Leakage current is the input current output current imbalance,Elevator Switch the leakage switch is only from the current to determine the leakage, it does not know the inverter will be through the harmonic (electromagnetic waves, parasitic capacitance) way leakage, and leakage value is greater than the normal leakage of the field value, Once the inverter starts to work will cause leakage protection switch action.
In summary, in the inverter side of the line can not install the leakage protector, and the need to install the motor dedicated air switch (AD type).
The following is a simple explanation of the letter to the customer format:
Xx elevator user unit:
Recently, I Division in the elevator daily practical workers encountered some users in the supply of elevator power supply on the way to set the leakage protection switch, resulting in the elevator can not work properly, the Division I technical staff to analyze the task of the elevator should not set the leakage protection switch, described as follows:
1. Elevator Switch Three-phase leakage protection switch from the structure point of view of the zero sequence current detector, current amplifier and electromagnetic trip device,Elevator Switch the zero sequence current value is equal to the three-phase current vector sum. When the three-phase current balance, the zero sequence current value is equal to zero, when the three-phase current is not balanced, the zero sequence current value is not equal to zero, when the zero sequence current value reaches a certain value (greater than the set value), after the current amplifier push off Check the work, leakage protection switch trip protection.
2. The current elevator products are using the most advanced AC variable frequency inverter (VVVF) speed control system to drive the elevator to run. As the system in the elevator every time the first need to provide users with three-phase elevator power supply rectifier into DC after the implementation of variable frequency frequency control, so in the three-phase elevator power supply rectification process,Elevator Switch according to the principle of rectifier circuit In the three-phase rectifier bridge will produce three-phase flat current, zero sequence current value is not equal to zero, leakage protection switch trip protection, resulting in the elevator can not run properly.
In summary,Elevator Switch the elevator power supply circuit can not install the leakage protection switch, otherwise it will make the elevator failure or not work properly.