Electrical Protection 3

What statement best describes the construction of a fusible link

• A metal encased device that detects overcurrent in heating appliances

• a metal alloy element enclosed in a small metal canister with 2 leads

• a fuse in metal surrounded by quartz silica sand

• a porcelain type fuse used in heating appliances

Fusible links are designed to interupt current flow when the current gets too high

• True

• False

Answer explanation

Fusable links interupt the current when excess temperature or heat melts the link

"HRC" stand for ...

• High rupturing capacity

• High rupturing current

• High resistance capacity

• High resisitance current

The ceramic fuse barrel of a HRC fuse has good _______________ characteristics

• Insulation and strength

• looks and strength

• mechanical strength and thermal

• insulation and thermal

The filler in HRC fuses is made of graded silica which has good ....

• thermal characteristics

• arc extinguishing properties

• insulation properties

• thermal conductivity

HRC fuses are used in installations where higher prospective short circuit voltages are present

• True

• false

Answer explanation

Used in installations where higher short circuit currents are present

A MCB trips by what type of action during overcurrent

• Solenoid coil action

• thermal

• magnetic

• bi -metal

What element is NOT part of the construction of an MCB?

• Arc chamber

• Bi-metal

• Reset lever

• Test button

A short circuit will operate a MCB by magnetic action

• True

• False

A MCB operating at twice the rated current of the device will trip by _______ action

• Magnetic

• timer

• Thermal

• A combination of thermal and magnetic