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Circuit Breakers
Miniature Circuit Breakers from 1 to 63 AMP in B, C and D trip curves
When deciding which miniature circuit breaker is best for any application, it is important to determine what type of protection is necessary. For these MCB's, there are two important factors to consider when choosing which breaker is appropriate:
- Supplementary or Branch Circuit Protection
- Supplementary protectors are the most common type, but since branch circuit protection is not required, a separate device such as a fuse or molded case circuit breaker must be used upstream
- Branch Circuit protectors are listed as a primary protection device and can be used alone without the need for an additional protection device
Determining the trip curve needed for your miniature circuit breaker
Miniature circuit breakers can come in 7 different trip curve ratings, with B, C and D being the most common. It is imperative that the correct trip curve is chosen the effectively protect the equipment that is downstream from this device. Listed below are the three most common trip curves along with a brief description of suitable applications:
- B-curve : Suitable for applications where protection against low level short circuit faults in control wiring is desired. Instantaneous trip is 3 to 5 x continuous rating of device (In). Applications include PLC wiring, business equipment,
lighting, appliances and some motors. Low magnetic trip point. - C-Curve : Suitable for applications where medium levels of inrush current are expected. Instantaneous trip is 5 to 10 x rating of device (In). Applications include small transformers, lighting, pilot devices, control circuits, and coils. Medium magnetic trip point.
- D-curve : Suitable for applications where high levels of inrush current are expected. Instantaneous trip is 10 to 20 x rating of device (In). The high magnetic trip point prevents nuisance tripping in high inductive applications such as motors, transformers, and power supplies.