Examples Of Coolant Control - Siemens SINAMICS S120 Equipment Manual

9.5

Examples of coolant control

For water-cooled devices, warm ambient air can condense on the cold surfaces of heat sink.
The resulting condensate can cause electrical damage such as leakage current bridges and
flashovers. Condensation must be avoided by means of an appropriate temperature of the
coolant by always maintaining the temperature of the heat sink above the dew point of the
ambient air. This can be achieved either by a permanently set and correspondingly high
coolant temperature, or by controlling the temperature of the coolant in accordance with the
ambient air and the relative humidity.
A temperature control of the coolant adds a temperature difference T
3 K ... 5 K above the condensation temperature to the ambient temperature T
setpoint T
temperature setpoint with the actual value at the coolant inlet T
via parameter r0037[19]. The coolant temperature control is performed by the three-step
controller with the aid of the servo motor connected to the 3-way valve.
The three-step controller has three switch positions for control of the servo motor:
● +Y1 for forward motion
● 0 for standstill
● –Y1 for backward motion
When the control deviation x exceeds the upper switching hysteresis x
switched on, when the deviation falls below the lower switching hysteresis x
is switched off. When the control deviation falls below the switching hysteresis in the
negative direction, the servo motor runs in the opposite direction until the control deviation
has been cleared and the servo motor is switched off.
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.
Water-cooled chassis power units for common cooling circuits
Manual, 08/2017, 6SL3097-4AM10-0BP0
Cooling circuit, coolant properties and protection against condensation
for the coolant temperature, see following figure. The control compares the
set
9.5 Examples of coolant control
of approximately
L
and forms the
U
, which can be accessed
act
, the servo motor is
u
, the servo motor
l
reaches the setpoint, the
act
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