SELF-HOLD THERMAL CONTROLS

Resettable Bimetallic Thermal Controls reliably limit operating temperatures within a pre-set range. But what happens when failure could be catastrophic? Often product designers want an extra level of safety to make sure that a circuit doesn’t overheat.

There are a number of ways to achieve an additional layer of safety into consumer products. First, you could use a secondary thermal control that would serve as a backup to the primary control in the application. This is certainly not the most cost effective method but you would have double reliability in your application as both controls could be tested for functionality. A second more economical way to add extra safety is to include a thermal fuse to totally shut down a circuit in a overheat condition. These devices are truly fuses so once they function, they must be replaced before the circuit is again operational.

The third, and usually more functional way, is to use a Self-Hold Thermal Control. These innovative devices contain is small internal heat source. Once a circuit opens due to temperature rise, the internal heat source is activated and keeps the thermal control in an open condition even as the actual application cools. The circuit will stay open until power is removed, shutting off the internal heat source and resetting the device. 

So, where a Thermal Fuse must be rewired into the circuit (hard), a circuit using a Self-Hold Thermal Control need only be unplugged for a period of time (easy), allowing the device to reset.