hi temp snap disc thermostats

hgmjr

Joined Jan 28, 2005
9,029
I think these work on the principle of a bi-metal strip. By bonding two thin pieces of metal together each with a different coefficient of thermal expansion, one of the two strips will expand to a greater length than the other and so the metal strip will deform and make or break a contact between the two terminals.

hgmjr
 

thingmaker3

Joined May 16, 2005
5,073
...and in the form of a slightly cupped disk, the difference in expansions makes a quick snap. This type of switch is often used as a thermal overload protection in motors.
 

KL7AJ

Joined Nov 4, 2008
2,208
...and in the form of a slightly cupped disk, the difference in expansions makes a quick snap. This type of switch is often used as a thermal overload protection in motors.

Yeah...most of the ones I've worked with had to be manually reset. My old HP 524 frequency counter had one of those, in case it overheated from all 347 vacuum tubes....yeah, like THAT was ever going to happen! :rolleyes:

Eric
 

thingmaker3

Joined May 16, 2005
5,073
Manual reset offers the opportunity to fix the root problem without undue torture to the system. Automatic reset allows the system to keep cycling into an overheat condition. I suspect the filaments in vacuum tubes last longer when they are cycled less. Locked rotor motors certainly do! :cool:
 
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