Siemens Sinamics S120 Manual page 341

From the control point of view, the servo motor on 3-way valve has an I behavior.
The dashed feedback is recommended for a stable control with P behavior.
The 3-way valve is controlled so that the path B-AB is opened when the coolant is cold. The
coolant is led past the heat exchanger and the heat sink is heated by the switching losses of
the power semiconductors. When the coolant inlet temperature T
three-step controller opens the 3-way valve and the path A-AB.
Figure 9-19 Principle of a flow control with 3-way valve as protection against condensation
Liquid-cooled chassis power units
Manual, (GH7), 11/2016, 6SL3097-4AM00-0BP7
Cooling circuit, coolant properties and protection against condensation
9.5 Examples of coolant control
reaches the setpoint, the
act
341