Siemens bt300 Operator's Manual page 94

Chapter 4 - Parameters and Menu Structure
Parameters (M3)
Actual value
Frequency
Sleep limit
(P3.12.2.7)
Feedforward function (P3.12.4.1)
Feedforward usually needs accurate process models, but in some cases, a gain + offset type of feedforward is
enough. The feedforward part does not use any feedback measurements of the actual controlled process value
(water level in the following Example). Siemens feedforward control uses other measurements which are
indirectly affecting the controlled process value.
Example:
You are controlling the water level of a tank by means of flow control. The desired water level has been defined
as a setpoint and the actual level as feedback. The control signal acts on the incoming flow.
Think of the outflow as a disturbance that can be measured. Based on the measurements of the disturbance, you
can try to compensate for this disturbance with a simple feedforward control (gain and offset) which is added to
the PID output.
This way, the controller will react much faster to changes in the outflow than if you had just measured the level.
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Building Technologies
Wake-up level
(P3.12.2.9)
Sleep delay
(P3.12.2.8)
Regulating mode
Figure 26: Sleep limit, Sleep delay, Wake-up level.
Siemens BT300 HVAC Drive
Sleep Regulating mode
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DPD01809
2016-06-07