3005 LO4 21 MCB Curve Types

This is an MCB (Miniature Circuit Breaker).

What current can run through it continuously forever?

• 4A

• 6A

• 12A

• 24A

• 48A

This is an MCB (Miniature Circuit Breaker).

What curve type rating is it?

• A

• B

• C

• D

• E

This is an MCB (Miniature Circuit Breaker).

If I put 24 Amps through it, what would happen?

• It will trip at anything over 6 amps

• It will trip at exactly 6 amps

• It will allow 24 amps for a short period of time, maybe a few seconds, and then trip

• It will allow about 24 amps for about 4 minutes and then trip

• It will allow 24 amps for up to 4 1/2 hours

This is the trip curve graph of a C curve MCB (Miniature circuit breaker).

If the MCB is marked at 6 amps, and 24 amps runs through it for half a second, would it trip?

• Yes, it is rated at 6A

• No, it is rated at 6A, and must trip at 6A, not more

• Yes, there is enough current at the rating of the C Curve MCB

• No, there is not enough current at the rating of the C Curve MCB

This is the trip curve graph of a C curve MCB (Miniature circuit breaker).

If the MCB is marked at 6 amps, and 35 amps runs through it for half a second, would it trip?

• Yes, it is rated at 6A

• No, it is rated at 6A, and must trip at 6A, not more

• Yes, there is enough current at the rating of the C Curve MCB

• No, there is not enough current at the rating of the C Curve MCB

This is the trip curve graph of a C curve MCB (Miniature circuit breaker).

If the MCB is marked at 6 amps, and 24 amps runs through it for 5 seconds, would it trip?

• Yes, it is rated at 6A

• No, it is rated at 6A, and must trip at 6A, not more

• Yes, there is enough current at the rating of the C Curve MCB

• No, there is not enough current at the rating of the C Curve MCB

This is the trip curve graph of a C curve MCB (Miniature circuit breaker).

If the MCB is marked at 6 amps, and 12 amps runs through it for 1 minute, would it trip?

• Yes, it is rated at 6A

• No, it is rated at 6A, and must trip at 6A, not more

• Yes, there is enough current at the rating of the C Curve MCB

• No, there is not enough current at the rating of the C Curve MCB

This is the trip curve graph of a C curve MCB (Miniature circuit breaker).

What would a C Curve MCB normally be used for?

• Normal domestic operations

• Motors and coils

• Hospitals and medical centres

• Lighting systems

This is the trip curve graph of a C curve MCB (Miniature circuit breaker).

Based on the C Curve characteristics, would we consider this MCB to generally trip at 7.5 times it's current value?

• No, it must be exactly 10 minus 5 equals 5 x Current value

• Yes, it is 7.5 x Current for under 1 second

• Yes, 7.5 is centre of 5 and 10 for any current no matter how long

• No, It will only trip at exactly 5 x Current rating, and not go higjher

If this MCB is marked C 20, then what is the 6 KA marking for?

• That is manufacture model number

• It can handle 6KA for a very short time, so it will not accidentally switch off if there is an electrical spike

• This figure represents its breaking capacity, also known as interrupting rating.

• This is an indicator of the wire size that must be used