Thermal Protections

It is more and more necessary to protect
equipments against over temperature effects.

This is particularly true for electrical
engines, transformers, power circuits.

Thermal protections are realised either
with a system of detection and measurement
of temperature with NTC or PTC thermistors
(see these chapters), or with a thermal
switch which opens the circuit to protect,
or for high powers a relay, or closes a
contact on a fan to refresh the equipment.

Thermal switch (frequently named, per mistake,
thermostat) is a bi metallic element which
operates with the metals dilatation : two
different dilatation coefficients (e.g. copper
and steel) are put together either by bonding
or electrolytic deposit, then cutted out in blades
or in discs stamped as a bowl.

When the temperature increases, copper which
expands more than steel, make a deformation of
the blade which bends or the discs which reverses,
this allows to open or close a circuit.

These switches are protected with a housing.
Several shapes are available and they can switched
off intensities from 1 to 25 Amp.

When the temperature decreases, the blade or disc
will recover its initial shape and re-establish
the contact.

An important differential is necessary to avoid a
too fast re-contacting and allows the equipment to
cool down before a re-starting.

The temperature imiting switch is a thermal switch
which needs a manual operation to re-start.

For any further information, don't hesitate to contact us.
By clicking Here