In the power electronic distribution wiring, when the equipment inside the screen is connected with the equipment outside the screen, it must pass through some special wiring terminals. These wiring terminals are combined, which is called terminal strip. The function of the terminal block is to connect the lines of the equipment inside the screen and the equipment outside the screen, and play the role of signal (current and voltage) transmission. With the terminal strip, the wiring is beautiful and convenient for maintenance. The connection between remote offline is mainly reliable and convenient for construction and maintenance

General equipment is controlled by PLC and upper computer. Generally, the input / output points of the PLC of the equipment are not directly connected to the actuator. Most of the input / output points are connected to the terminal strip before / after entering / leaving the PLC. After reading the circuit diagram, it is found that these circuit boards are generally conversion circuits, which are finally connected to the actuator

In fact, I found it possible to connect directly to the actuator. Why do you have to connect it to the circuit board so troublesome? Is it to save input / output points? (for example, one output point controls multiple groups of relays, and this relay controls multiple signals.)
The main functions of the terminal block are as follows:

1. Isolation function: generally, the form of PLC controlling other equipment is weak current controlling strong current. Strong current equipment can be isolated from PLC through intermediate relay, but it can also play a control role at the same time. In addition, for example, if the external signal is short circuited and directly connected to the module, the module may be burned, and even if the circuit board or relay is burned, the cost is small

2. Anti interference. For example, some loads are of the nature of interference source. For example, frequency converters have high-frequency harmonics, which is easy to interfere with the control of PLC

3. It is recommended to refer to the product design requirements in detail before design. The design method recommended in the manual is to meet the design ideas and methods of safety, isolation and anti-interference

However, the function of terminal strip is mainly signal isolation, including the isolation between module channel and backplane bus and the isolation between channel and module power supply. Most modules are separated by these two methods. Refer to the module specification for details. If the channel is not isolated from the backplane bus, the power supply of the CPU needs to be grounded with the module common terminal mana. If the module L + is not isolated from the channel, the module 24V power supply m needs to be grounded together with the module common terminal mana. If the non isolated module fails to do the above, the common mode voltage between different power supplies will affect the normal measurement, and even the reading overflow phenomenon will occur. If the sensor is not isolated, the power supply of the sensor also needs to be grounded together with the common end of the module. The specific method is to short circuit the negative end of the signal to the module common terminal mana during four wire current or voltage measurement