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Beschreibung:
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Differences amoung overcurrents, overloads and short circuits
Overcurrents
NEC defines and overcurrent as any current in excess of the rated current of equipment of the ampacity of a conductor. An over current is the result of an overload, short circuit, arc or ground fault. Effects of overcurrent include fires, conductor insulation damage and equipment damage.
Overloads
According to NEC, an overload is the operation of equipment in excess of normal, full-load rating, or of a conductor in excess of rated ampacity that, when it persists for a sufficient length of time would cause damage or dangerous overheating. An overload is NOT a short circuit, ground or arc fault.
Short Circuits
A short circuit is an overcurrent which greatly exceeds the normal full load current of the circuit. Also, as the name infers, a short circuit leaves the normal current carrying path of the circuit and takes a short-cut around the load and back to the power source. A short circuit is an overcurrent but not an overload.
Circuit breaker components
Although low and medium voltage circuit breakers have unique designs that are specific to amperage, voltage and application, there are five main components that are universal across the different types of circuit breakers. The five universal circuit breaker components are:
Frame – Protects internal parts of the circuit breaker from outside materials
Operating mechanism – Provides a means of opening and closing the circuit breaker
Contacts – Allows the current to flow through the circuit breaker when closed.
Arc extinguisher – Extinguishes an arc when the circuit breaker interrupts a fault.
Trip unit – Opens the operating mechanism in the event of a prolonged overload or short circuit.
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