PPTC circuit protection for line-voltage devices

April 12, 2007
Polymeric positive-temperature-coefficient (PPTC) devices have long been used on low-voltage devices and systems to protect circuits from overcurrent (short circuits) and overtemperatures.

Carbon matrix embedded in polymer provides a low-resistance electrical path.

Excess current heats device and polymer expands. Expansion breaks conductive carbon chains to increase resistance.

Now Raychem Circuit Protection, a subsidiary of Tyco Electronics, Menlo Park, Calif. (raychem.com), has developed versions that work with line voltages up to 240 V.

The solid-state components are made of a cross-linked polymer with a conductive matrix of carbon embedded in it. When heated, which can be due to overcurrent or overtemperature, the polymer expands quickly. This, in turn, breaks the vast majority of conductive carbon paths, so resistance becomes very high and current flow extremely low. Operations can reset the device by turning off the power. This lets the polymer cool, compress, and rebuild the carbon matrix. The devices can be tripped and reset at least 6,000 times with little loss of electrical properties. The devices make it possible to incorporate primary-side transformer protection and can be used to help protect motor windings from damage from fault conditions or application overloading.


Sponsored Recommendations

How BASF turns data into savings

May 7, 2024
BASF continuously monitors the health of 63 substation assets — with Schneider’s Service Bureau and EcoStruxure™ Asset Advisor. ►Learn More: https://www.schn...

Agile design thinking: A key to operation-level digital transformation acceleration

May 7, 2024
Digital transformation, aided by agile design thinking, can reduce obstacles to change. Learn about 3 steps that can guide success.

Can new digital medium voltage circuit breakers help facilities reduce their carbon footprint?

May 7, 2024
Find out how facility managers can easily monitor energy usage to create a sustainable, decarbonized environment using digital MV circuit breakers.

The Digital Thread: End-to-End Data-Driven Manufacturing

May 1, 2024
Creating a Digital Thread by harnessing end-to-end manufacturing data is providing unprecedented opportunities to create efficiencies in the world of manufacturing.

Voice your opinion!

To join the conversation, and become an exclusive member of Machine Design, create an account today!