Siemens Module B3 ユーザーズマニュアル

 

 

 

 

 

 

 

   

 

 

 

 

T I A  Training Document 

Page 21 of 64 

  Module 

 

The discrete controllers just discussed have, as mentioned before, the advantage of being simple. 

The controller itself as well as the actuator and the final control element are of a simpler nature and 

thus less expensive than for continuous controllers.  However, discrete controllers have a number of 

disadvantages. If high loads, such as large electrical motors or cooling systems have to be operated, 

high peak loads can occur that can overload the power supply.  For these reasons, we often don’t 

switch between “Off“ and “On“, but between a full load and a base load -with a clearly lower use of 

the actuator or final control element.  But even with these improvements, a continuous controller is 

not suitable for many applications. Imagine a car engine whose speed is governed discretely.  There 

would be nothing between idle and full throttle. Aside from it probably being impossible to transfer 

the power during a sudden full throttle suitably over the tires onto the road, such a car would 

probably be quite unsuitable for street traffic. For such applications, continuous controllers are used 

for that reason. Here, the mathematical relationship that the controlling element establishes between 

system deviation and controller output variable is theoretically virtually limitless.  In practice, 

however, we differentiate among three classical basic types that are discussed in greater detail 

below.   

Preface     Fundamentals     Discontinuous Action Controller     Controller Block (S)FB41     Setting the System     Appendix 

B3 

Issued: 02/2008                                                                                                                                     Control Engineering with STEP 7