Overcurrent Devices (1)

List four potential overcurrent situtations.

1. Overloads

2. Ground faults

3. Lighting surges

4. Short circuits

How can an overload condition be defined?

The level of overcurrent is a moderate percentage above the normal current for that circuit

What are two current ratings for an overcurrent device?

1. Continuous

2. Interrupting

What are the two main types of circuit breakers?

1. Instantaneous (magnetic)

2. Time limit (thermal magnetic)

When can instantaneous circuit breakers be used?

Only for short circuit protection

What are instantaneous circuit breakers also known as?

Magnetic / Instantaneous magnetic trip circuit breakers

How long does it take for an instantaneous circuit breaker to open a circuit?

A few milliseconds

What are the advantages of an instantaneous circuit breaker?

1. High speed

2. Precision

3. Low overcurrent sensitivity

4. Lack of sensitivity due to temperature change