ABB UMC100-FBP - Thermistor (PTC) Motor Protection Acc. to en 60947-8 (Type a Sensors)

- 49 - UMC100-FBP
Universal Motor Controller
UMC100-FBP
Technical Description
FieldBusPlug / Issue: 03.2012
Thermistor (PTC) Motor Protection acc. to EN 60947-8 (type A sensors)
PTC thermistors are semiconductor elements with a very high positive temperature coefficient. They are
embedded directly in the phase windings of the stator. In contrast to the thermal overload protection that
responds to the load current, the thermistor protection responds to the change in thermistor resistance
due to temperature change in the motor windings.
The thermistors are selected to have a rated operating temperature that corresponds to the insulation
class, type and construction of the motor. At the rated temperature the thermistor resistance increases
sharply up to the hot temperature resistance value.
The UMC senses this abrupt change in the resistance. When thermistor protection is activated there is
also an internal supervision which detects open or short-circuit faults from the thermistor circuit.
T1 T2 Ca Cb
u 
Motor with intergated
PTC sensors
2CDC 342 021 F0209
 Connect the PTC to the T1/T2 terminals of the UMC.
Relevant Parameters:
•PTC