83003702.K Operating Instruction
Type KPC 108-L-U/S
page 37
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Single-Stage Hermetic Compliant SCROLL Motor-Compressor
Type ZR xx K3E-TWD-561
Electronic Motor Protection
The electronic motor protection system as used in all ZR 90 K3* ... ZR 380 KC* models is identified by a “W” as the
center letter in the motor code. This system utilizes the temperature dependent resistance of thermistors (also called
PTC resistances) to read the winding temperature. A chain of four thermistors connected in series is embedded in the
motor windings so that the temperature of the thermistors can follow the winding temperature with little inertia. An
electronic module is required to process the resistance values and trip a control relay depending on the thermistor
resistance. The resistance curve can be designed for different operating points, the nominal response
temperature (NAT), e.g. 80 °C, 130 °C, 140 °C and must comply with the tolerances laid out in the standard DIN 44081.
