三相插座应用

三相插座应用 As a result of the electrical design of personal safety protection put forward higher requirements. The TN system uses a lot of in the design of TN-C system electrical equipment in the shell is protected in different degrees with the voltage to the ground, PEN line maintenance has potential shortcomings and can not be isolated, and while the TN-S TN-C-S system obviously overcomes these shortcomings that TN-C system, PE line under normal conditions without return zero current, N line can be isolated, so that the TN - S and TN - C - S system has been used in a large amount. In order to further protect the safety of people, "GB leakage protection installation and operation" (GB13955 - 92) regulations, required to all electrical equipment, in damp places a hand-held electric tool equipped with residual current circuit breaker protection. Although a number of senior high school entrance examination system design about protective measures, but due to the three-phase socket and electrical equipment production failed to complete, which have been built in the project, three there are some problems with the use of electric equipment. Overview of the use of three-phase sockets in 1 TN and TT systems TN - S, TN - C - S and TT system set up a dedicated PE line for the three-phase equipment, direct connection socket is safe, and the need for the electrical equipment of the three-phase power supply socket power supply, the situation is complicated. Because the system needs the three-phase five polar socket, and currently in civilian areas has not three-phase five pole socket and plug standard, although the "plug and socket and coupler Industry General requirements" (GB11918 - 89), "industrial plug and socket and plug and socket coupler size interchangeability requirements" (GB11919 - 89) regulations the standard plug socket of the coupler and the industry, but because of its application scope, production cost and other reasons, it has not yet universal application. The existing three-phase four pole socket has been unable to meet the needs of the TT system, and the TN-S TN-C-S, there are four very not corresponding to the five line system and power socket problem. In addition, even if there are five socket, because of the domestic production of the electric equipment is connected with the socket of the three-phase (hereinafter referred to as the "plug-in three-phase equipment") almost all of the three-phase quadrupole plug connection, also is not very good, this is because the plug-in is three-phase equipment design for the past TN C system commonly used in production. In the N line and the equipment inside the enclosure are connected to form the PEN line, apparently not very well with TN - S, TN - C - S and TT systems to adapt. These problems are abundant in engineering. For example, the power socket box will be used in all kinds of engineering, setting the domestic production of the socket box with the three-phase socket is basically four socket, the socket box is no exception to this rule is used in the TT system, the TN-S and TN-C-S engineering. 3-phase 4-pole socket is designed according to the provisions of TN-C system, PEN line terminal fourth pole socket. The need to separate the N line and PE line TN - S, TN - C - S and TT system, the N line and PE line can simultaneously access the fourth terminal, so the socket on the fourth terminals should be connected to the neutral line (N line) or access protection line (PE line)? The fourth terminal of the four pole socket marks the grounding mark. It seems that the PE line should be connected to the fourth terminal. Where can the neutral line be located? Analysis on the actual situation of plug-in three-phase equipment, In general, these three-phase power equipment use two control loops, and the control circuit often adopts 220V single-phase power supply, so the neutral line should also be supplied to the power equipment. In actual engineering, the position of the fourth pole of the socket, the connection of the N line and the connection of the PE line all exist. There are problems with 2 three-phase four pole socket, TT and TN-S TN-C-S system (1) the TN-S system: The neutral line (N line) of the TN S system is separated from the protective line (PE line). They are only connected to the grounding point of the power system. The load side only has the PE line to do repeated earthing and is connected with the exposed conductive part of the electrical device. When the fourth pole meets the neutral line (N line) of the three-phase socket, the plug-in three-phase equipment becomes a TN - C protection system. Because the N line did not do repeat grounding in into the family, so in the normal condition, the zero sequence voltage U0 plug-in type three-phase equipment shell with high admiral, once the phase to ground short circuit, and power supply line N line section is equal to the phase section, dangerous voltage equipment shell will produce 110V. If the N line cross section of the mains is equal to the cross section of the 1/2 line, the shell of the device will produce a dangerous voltage up to 147V. In this case, the security of plug-in three-phase equipment is not as high as in the TN - C system. The fourth pole three-phase socket connected PE line, the plug-in type three-phase equipment two I0 loop current flowing through the PE line, it not only plug the three-phase equipment shell produces zero voltage U0, and through the PE line to the non zero potential transfer to other equipment shell, thereby undermining the security of the entire system. (2) TN-C-S system: In the TN C S system, there is a part of the N line and PE line is one, usually for the front part. The system often repeats the PEN line at the entrance to the home. After entering the house, the N line is separated from the PE line, and the two can not be connected again. The electrical device is exposed and the conductive part is connected only to the PE line. When the fourth pole of the three-phase socket meets the N line, the plug-in three-phase equipment becomes completely TN - C system protection, so that the security of the plug-in three-phase equipment is lower than the safety level of the system design. When the fourth pole of the three-phase socket is connected to the PE line, the safety of the whole system is destroyed as in the case of the TN S system.