3.7.2 Operating principle of the re-cooling unit
The re-cooling unit dissipates the heat loss from the drive. The deionized water in the internal
water circuit absorbs the heat of the drive power unit which is to be dissipated. A maintenance-
free circulating pump pumps the hot water into the heat exchanger. The external raw water
circuit cools the hot deionized water. The cooled deionized water is pumped back to the drive.
For additional information, refer to the operating instructions of the re-cooling unit.
3.7.3 The internal deionized water circuit
The internal water circuit is filled with deionized water (deionized, fully-desalinated water). The
conductivity of the cooling water must be ≤ 1 µS/cm in operation.
NOTICE
Material damage due to inadmissible additives in the deionized water
Inadmissible additives in the deionized water can cause the cooling system to fail. This could
damage the drive.
● Use only deionized water that corresponds to the specifications. The specification of the
deionized water can be found in the documentation for the re-cooling unit.
● The level in the deionized water expansion tank and the pump motor circuit breakers are
monitored. Any water leak is also detected.
● The pressure of the deionized water is displayed on a manometer. If the flow is excessively
low, then the re-cooling unit automatically switches over the pumps.
● The deionized water temperature is measured. The value is used for controlling the three-
way valve
● If one of the monitoring devices responds, a signal is output or the re-cooling unit and drive
are switched off.
Deionized water requirements
Table 3-1 Deionized water requirements
Value
Conductivity during filling < 10 μS/cm
Evaporation residue < 20 mg/l
pH value 5 to 9
Description
3.7 Re-cooling unit
SINAMICS PERFECT HARMONY GH150 6SL3825
Operating Instructions 05/2020 33
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