Resistors Glossary Terminology
Fusible Resistor (Fuse Resistor, Circuit Protect Resistor)
A resistor designed to protect a circuit against overload; its resistance limits current flow and thereby
protects against surges when power is first applied to a circuit; its fuse characteristic opens the circuit
when current drain exceeds design limits.
Thermal Cutoff Resistor
The maximum nominal resistance value at which the rated power can be applied continuously without
exceeding the maximum working voltage is the critical resistance value. The rated voltage is equal to
the maximum working voltage in the critical resistance value. If the circuit designs permits, the choice
of a high ohmic value resistor or divider network will eliminate this consideration.
A thermal fuse is a cutoff which uses a one-time fusible link. Unlike the thermostat which automatical-
ly resets itself when the temperature drops, the thermal fuse is more like an electrical fuse: a single-use
device that cannot be reset and must be replaced when it fails or is triggered. A thermal fuse is most
useful when the overheating is a result of a rare occurrence, such as failure requiring repair (which
would also replace the fuse) or replacement at the end of service life.
Token offers “Thermal Cut-off Resistor”, a thermal Cut-offs is a fusible alloy and a resistor is a volt-
age divider, both are surrounded by a ceramic cement with special resin. Under normal operating tem-
peratures the fusible alloy joins the two lead wires within the body of the cutoff and the power resistor
acts as a normal function resistor. When the preset temperature of the cutoff is reached, the fusible
alloy melts and with the aid of the special resin, complete cutoff is ensured.
Thermal fuse resistors are usually found in heat-producing electrical appliances such as coffeemak-
ers and hair dryers. They function as safety devices to disconnect the current to the heating element in
case of a malfunction (such as a defective thermostat) that would otherwise allow the temperature to
rise to dangerous levels, possibly starting a fire.
Version 2010
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