The world's PLC products can be divided into three major genres by region: one genre is an American product, one genre is a European product, and one genre is a Japanese product. PLC technology in the United States and Europe is independently researched and developed under isolation, so there are significant differences between PLC products in the United States and Europe. The Japanese PLC technology was introduced by the United States, and has certain inheritance to the US PLC products, but Japan's main push products are positioned on small PLCs. The United States and Europe are known for large and medium-sized PLCs, while Japan is known for small PLCs.
American PLC products
The United States is a PLC producing country with more than 100 PLC manufacturers, such as AB, General Electric (GE), MODICON, Texas Instruments, and Westinghouse. Among them, AB is the largest PLC manufacturer in the United States, and its products account for about half of the US PLC market.
AB's product specifications are complete and varied, and its main large and medium-sized PLC products are PLC-5 series. This series is a modular structure. When the CPU module is PLC-5/10, PLC-5/12, PLC-5/15, PLC-5/25, it belongs to medium-sized PLC. The I/O point configuration range is 256~1024 points. When the CPU module is PLC-5/11, PLC-5/20, PLC-5/30, PLC-5/40, PLC-5/60, PLC-5/40L, PLC-5/60L, it is a large PLC, I / O points can be configured up to 3072 points. The PLC-5/250 is the most powerful in this series, with up to 4096 I/O points, with powerful control and information management functions. The mainframe PLC-3 can be configured up to 8096 I/O points. AB's small PLC products include the SLC500 series.
GE 's representative products are: small units GE-1 , GE-1/J , GE-1/P, etc., except for GE-1/J , all adopt modular structure. GE - l is used in switching control systems and can be configured up to 112 I/O points. The GE-1/J is a more compact product with up to 96 points of I/O points. GE-1/P is an enhanced product of GE-1 , adding some functional commands (data operation instructions), function modules ( A/D , D/A, etc.), remote I/O functions, etc., and its I/O points. Up to 168 points can be configured. Medium-sized machine GE- III, which adds interrupt, fault diagnosis and other functions than GE-1/P , and can be configured up to 400 I/O points. The mainframe GE- V, which adds some data processing, table processing, subroutine control and other functions to the GE- III, has strong communication functions and can be configured up to 2048 I/O points. The GE- VI /P can be configured up to 4000 I/O points.
Texas Instruments ( TI )'s small PLC new products are 510 , 520 and TI100 , medium-sized PLC new products are TI300 , 5TI, etc., large PLC products are PM550 , 530 , 560 , 565 and other series. In addition to the TI100 and TI300 without networking functions, other PLCs can communicate to form a distributed control system.
MODICON has M84 series PLC . Among them, M84 is a small machine with analog control and communication with the host computer. The maximum I/O point is 112 points. M484 is a medium-sized machine. It has strong computing functions and can communicate with the host computer. It can also be connected to multiple networks. The maximum expandable I/O point is 512 points. The M584 is a mainframe with a large capacity, strong data processing and network capabilities, and a maximum expandable I/O point of 8192 . M884 enhanced medium-sized machine, which has the structure of a small machine and the control function of the mainframe. The host module is equipped with two RS-232C interfaces, which can conveniently carry out networking communication .
In the rectifier circuit; the use of diodes in series can increase the back pressure withstand value (usually the sum of the back pressure of all diodes, but it is best to use diodes of the same specification).
In the voltage stabilization circuit; the series connection of the diode is equal to the sum of the voltage stabilization value of the diode. The use of diodes in parallel is theoretically the sum of rated currents, but considering that it is impossible to be absolutely symmetrical, they can only be used below 80% of the total.
TVS transient suppressor diodes work in the same way as regulator diodes, but there are structural differences.The biggest difference is that the PN junction area composed of the general regulator diode is very small, it can withstand the reverse current is small.
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