YASKAWA CPS-150F 电源模块

YASKAWA CPS-150F 电源模块 

YASKAWA CPS-150F 电源模块 

1．来自空间的辐射干扰。空间辐射电磁场(EMI)主要是由电力网络、电气设备的暂态过程、雷电、无线电广播、电视、雷达、高频感应加热设备等产生的，通常称为辐射干扰，其分布极为复杂。若PLC系统置于其射频场内，就会受到辐射干扰，其影响主要通过两条路径：一是直接对PLC内部的辐射，由电路感应产生干扰；二是对PLC通信网络的辐射，由通信线路感应引入干扰。辐射干扰与现场设备布置及设备所产生的电磁场大小特别是频率有关，一般通过设置屏蔽电缆和PLC局部屏蔽及高压泄放元件进行保护

YASKAWA CPS-150F 电源模块 

2．来自系统外引线的干扰。主要通过电源和信号线引入，通常称为传导干扰。这种干扰在我国工业现场较为严重，主要有下面三类：

第一类是来自电源的干扰。实践证明，因电源引入的干扰造成PLC控制系统故障的情况很多，笔者在某工程调试中遇到过，后更换隔离性能更高的PLC电源问题才得到解决。

PLC系统的正常供电电源均由电网供电，由于电网覆盖范围广，它将受到所有空间电磁干扰而在线路上感应电压和电流，尤其是电网内部的变化、开关操作浪涌、大型电力设备起停、交直流传动装置引起的谐波、电网短路暂态冲击等，都通过输电线路传到电源原边。PLC电源通常采用隔离电源，但因其机构及制造工艺等因素使其隔离性并不理想。实际上，由于分布参数特别是分布电容的存在，绝对隔离是不可能的。

第二类是来自信号线引入的干扰。与PLC控制系统连接的各类信号传输线，除了传输有效的各类信息之外，总会有外部干扰信号侵入。此干扰主要有两种途径：一是通过变送器供电电源或共用信号仪表的供电电源串入的电网干扰，这往往被忽视；二是信号线受空间电磁辐射感应的干扰，即信号线上的外部感应干扰，这种往往非常严重。

由信号引入的干扰会引起I/O信号工作异常和测量精度大大降低，严重时将引起元器件损伤。对于隔离性能差的系统，还将导致信号间互相干扰，引起共地系统总线回流，造成逻辑数据变化、误动和死机。PLC控制系统因信号引入干扰造成I/O模件损坏数相当严重，由此引起系统故障的情况也很多。

YASKAWA CPS-150F 电源模块 

YASKAWA CPS-150F Power module

1. Radiation interference from space. Space radiation electromagnetic field (EMI) is mainly generated by power networks, transient processes of electrical equipment, lightning, radio broadcasting, television, radar, high-frequency induction heating equipment, etc., usually called radiation interference, and its distribution is extremely complex. If the PLC system is placed in its radio frequency field, it will be affected by radiation interference, which is mainly through two paths: one is the direct radiation inside the PLC, which is interfered by the circuit induction; The second is the radiation to the PLC communication network, which is induced by the communication line. Radiation interference is related to the field equipment layout and the size of the electromagnetic field generated by the equipment, especially the frequency, and is generally protected by setting shielded cables and PLC local shielding and high voltage release elements

YASKAWA CPS-150F Power module

2. Interference from leads outside the system. It is mainly introduced through power and signal lines and is often referred to as conducted interference. This kind of interference is more serious in our country's industrial site, there are the following three types:

The first is interference from the power supply. Practice has proved that many cases of PLC control system failure caused by the interference introduced by the power supply, the author encountered in a project debugging, and the problem of replacing the PLC power supply with higher isolation performance was solved.

The normal power supply of the PLC system is powered by the power grid, due to the wide coverage of the power grid, it will be affected by all space electromagnetic interference and induction voltage and current on the line, especially changes in the power grid, switching operation surge, large power equipment start and stop, AC and DC transmission device caused by harmonic, grid short circuit transient impact, etc., are transmitted to the original side of the power supply through the transmission line. PLC power supply usually uses isolated power supply, but due to its mechanism and manufacturing process and other factors, its isolation is not ideal. In fact, absolute isolation is not possible due to the presence of distributed parameters, especially distributed capacitors.

The second type is interference introduced from signal lines. All kinds of signal transmission lines connected with the PLC control system, in addition to the effective transmission of all kinds of information, there will always be external interference signal intrusion. There are two main ways of this interference: one is through the transmitter power supply or the power supply of the shared signal instrument into the grid interference, which is often ignored; Second, the signal line is interfered by electromagnetic radiation induction in space, that is, the external induction interference on the signal line, which is often very serious.

The interference introduced by the signal will cause the abnormal work of the I/O signal and the measurement accuracy will be greatly reduced, and it will cause damage to the components in serious cases. For the system with poor isolation performance, the signals will interfere with each other, causing the bus backflow of the common ground system, resulting in logical data changes, misoperation and crash. PLC control system due to signal interference caused by I/O module damage is quite serious, resulting in a lot of system failures.

YASKAWA CPS-150F 电源模块