DCS系统DSMB179 57360001-MS模块的操作DSMB 179 

继电器电路FA-M3的输入/输出点通常直接连接到外部设备。然而，在以下情况下，继电器应放置在控制器的输入/输出点和外部设备之间：-控制器远离外部设备，容易受到现场噪声干扰。-控制器应连接至产生高压噪声的设备需要澄清其他控制线路之间关于处理各自信号的责任的关系需要包括一个手动操作电路，作为I/O设备故障的备用电路。联锁处理特定输出时，需要联锁电路，例如不能同时打开的电机正反转输出。在这种情况下，安装外部联锁电路可使两个继电器线圈的“b”触点中的一个在通电时切断另一个。图A3.13显示了联锁电路的示例。

输出短路保护

如果连接到FA-M3输出端子的任何负载短路，则会产生过多的短路电流，并且外部接线可能会燃烧或产生异常热量。因此，通常在输出电路中安装保险丝，以确保短路负载情况下的安全，并将FA-M3的损坏降至最低。建议使用外部保险丝，尤其是对于没有内置保险丝或短路保护器的输出模块。图A3.12是配备输出短路保护熔断器的FA-M3的示例。请注意，这些保险丝并不用于保护内部输出元件免受可能的损坏。此外，这些保险丝在短路负载以外的故障模式下可能无法熔断。FA-M3的电源块包含一个内置的电源顺序电路，当发生瞬时电源故障或电压降低时，该电路可防止系统发生故障。该系统有两种检测电源故障的模式；一种是标准模式，另一种是即时检测模式。根据使用的电源模块或CPU模块的类型，使用即时检测模式有一些限制，如下表所示。默认（出厂设置）模式为标准模式。

Relay Circuits The input/output points of the FA-M3 are normally connected directly to external devices. Relays, however, should be placed between the input/output points of the controller and the external devices in the following cases: - The controller is far away from the external devices and is susceptible to noise interferences in the field. - The controller is to be connected to devices that will generate high-voltage noise. - There is a need to clarify the relationship between other control lines with regards to the responsibility of handling respective signals. - A manually operated circuit needs to be included as a backup against failure of the I/O equipment.

Interlocking An interlock circuit is required when you handle particular outputs, such as those for the forward and reverse rotation of a motor that must not turn on at the same time. In such a case, installing an external interlock circuit allows one of the “b” contacts of the two relay coils to cut off the other when energized. Figure A3.13 shows an example of an interlock circuit.

Protection against Output Short-circuit 

If any of the loads connected to the output terminals of the FA-M3 are short-circuited, an excess short-circuit current flows and there is the possibility that the external wiring will burn or there will be a generation of abnormal heat. It is therefore common practice to install fuses in the output circuits to ensure safety in the case of short-circuited loads and minimize damage to the FA-M3. Use of external fuses is recommended, especially for output modules that do not have built-in fuses or short-circuit protectors. Figure A3.12 is an example of an FA-M3 that is equipped with output short-circuit protection fuses. Note that these fuses are not intended to protect internal output elements against possible damage. In addition, these fuses may fail to blow in failure modes other than short-circuited loads.The power supply block of the FA-M3 incorporates a built-in power sequence circuit which prevents the system from malfunctioning when a momentary power failure or voltage reduction occurs. This system has two modes of detecting power failures; one is the standard mode and the other is the immediate detection mode. There are restrictions on the use of the immediate detection mode, as summarized in the table given below, according to the type of power supply module or CPU module used. The default (factory setting) mode is the standard mode.