TABLE OF CONTENTS Fuses act as a weak link in a circuit. They reliably rupture and isolate the faulty circuit under overload and short circuit fault conditions so that equipment and personnel are protected. Following fault clearance they must be manually replaced before that circuit may be put back into operation. Striker pins are available on some designs such that remote alarms may be initiated on fuse operation.
Miniature circuit breakers (MCBs) or moulded case circuit breakers (MCCBs) are also overcurrent protection devices often with thermal and magnetic elements for overload and short circuit fault protection. Earth leakage protection, shunt trip coils and undervoltage releases may also be incorporated in the designs. As a switch they allow isolation of the supply from the load. Normally the MCB requires manual resetting after a trip situation but solenoid or motor driven closing is also possible for remote control.
This chapter describes the various types of fuse and MCB together with their different uses and methods of specification. Examples and calculations for correct selection of different applications are also given.
Table 11.1 gives a summary of different fuse types, their uses, advantages and disadvantages. Table 11.2 summarizes some current relevant standards covering fuses. There are various categories ranging from subminiature electronic and solid state device protection fuses, power types (expulsion and high rupturing capacity (HRC)) to 72 kV.
| Category | Types | Use | Advantages and disadvantages |
|---|---|---|---|
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