MVME188A 控制器 备件卡件模块

MVME188A 控制器 备件卡件模块

为使PLC能可靠工作，在硬件与软件两个方面PLC厂家都采取了很多措施，对一些特殊可靠要求的PLC，还有相应的特殊的措施，如热备、冗余等等。这在介绍PLC的特点时已作了叙述。可靠措施的目的是增加PLC平均故障间隔时间、MTBF（MeanTimeBetweenFailure）及减少PLC的平均修复时间、MTTR（MeanTimeToRepair），以提高PLC的有效度A（Availability）。

A=MTBF/(MTBF+MTTR)

式中A--有效率

MTBF--平均故障间隔时间

MTTR--平均修复时间

当然，A值越大越好，它可使PLC系统得到充分的利用，是为什么要使用PLC的重要指标。而从上式可知，MTBF越大，MTTR越小，则A越大。所以，PLC的可靠措施都是围绕提高MTBF及MTTR值进行的。

鉴于可靠工作是PLC的重要特点，至关重要，故有关提高MTBF及降低MTTR的措施如何，以及PLC的MTBF与MTTR值也成为PLC性能的重要指标。

MVME188A 控制器 备件卡件模块

In order to make PLC work reliably, PLC manufacturers have taken a lot of measures in both hardware and software, and for some PLC with special reliability requirements, there are corresponding special measures, such as hot backup, redundancy and so on. This has been described in the introduction of PLC characteristics. The purpose of reliable measures is to increase the mean time between PLC failures, MeanTimeBetweenFailure (MTBF), and reduce the mean time between PLC repairs, MTTR (MeanTimeToRepair), so as to improve the Availability of PLC.

A=MTBF/(MTBF+MTTR)

Where A is efficient

MTBF- Mean time between failures

MTTR- Average repair time

Of course, the larger the A value, the better, it can make full use of the PLC system, is an important indicator of why to use PLC. As can be seen from the above formula, the larger the MTBF, the smaller the MTTR, the larger the A. Therefore, the reliable measures of PLC are around improving MTBF and MTTR values.

In view of the fact that reliable work is an important feature of PLC, it is crucial to improve MTBF and reduce MTTR measures, as well as the MTBF and MTTR values of PLC have also become important indicators of PLC performance.