Operating Instructions

Chapter 4 - Parameters and Menu Structure
Parameters (M3)
101 | 187
Siemens Industry, Inc.
Siemens BT300 HVAC Drive
DPD01809
Smart Infrastructure
2019-05-29
Figure 26: Sleep limit, Sleep delay, Wake-up level.
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.
11106.emf
Actual value
Wake-up level
(P3.12.2.9)
Frequency
Sleep limit
(P3.12.2.7)
Sleep delay
(P3.12.2.8)
SleepRegulating mode Regulating mode