Literature
Technical Tips & FAQs
PTC Thermistor protection using CEP7-EPT Side Mount Module
Question: What are the differences between the CEP7-EPT and the old RT3/RT7 for thermistor protection?
Answer: The RT3 and RT7 were stand-alone devices. The CEP7-EPT must be used in tandem with a CEP7-EE__ Overload Relay. Other than that, the same features can be found on both, but installation is the question.
| Model Features | CEP7(S)-EE + CEP7-EPT |
RT7-E1 | RT7-E2 |
|---|---|---|---|
| Thermal overload protection | • | • | • |
| Short-circuit/open-circuit protection in the sensor measuring circuit | • | • | • |
| Trip indication (Red LED) | • | • | • |
| Automatic reset | • | • | • |
| Manual reset | • | ||
| Remote reset (external button) | • | • | |
| Storage of switching status in memory | • | ||
| Test button | • | • | |
| Power-on indication (Green LED) | • | • | • |
Often installed in the motor stator windings, Positive Temperature Coefficient (PTC) resistors –known as thermistors - increase their resistance with an increase in temperature. This increase in resistance alerts equipment of a rise in motor temperature.
The characteristic comparison between the two products (RT3/RT7 vs. CEP7-EPT) shows application similarity in the technical information and rated values. CEP7-EPT is a suitable application replacement item for the RT3/RT7 since this side module runs independently from the overload portion – and you can just have PTC protection without having any current flowing through the CEP7.
Categories: Motor Protection
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