C vs D Curve Circuit Breakers, What's the Difference?

Q: What's the difference between B, C, and D curve circuit breakers?


A: All Circuit Breakers carry a current rating (In) which is the amount of current the breaker can carry continuously. The curve type (B, C, D, etc...) designates the instantaneous trip current range, or the amount of current at which the breaker will trip  without causing a time delay. Generally, the higher the current spike, the faster the  breaker will trip. Below you'll find a list of the the most common curve types and their  instantaneous trip ratings.

B Curve: Trips above 3 times In up to 5 times In
C Curve: Trips above 5 times In up to 10 times In
D Curve: Trips above 10 times In up to 20 times In

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Circuit Protection

• CP - Overview
• CP - MCCBs
• CP - Supplementary Protectors
• CP - Fusible Switches

• CP - Disconnects
• CP - Non-fused Load Switches
• CP - Fuses

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Technical Info for Circuit Protection / Fuses / Disconnects

• FAZ Series Supplementary Protectors 
• FAZ-NA Series Miniature Circuit Breakers 
• WMZT Miniature Circuit Breakers Technical Specs 
• MCCB, Fuji BW Series 15A-125A Tech Specs 
• MCCB, Fuji BW Series 125A-250A Tech Specs 
• MCCB, Fuji BW Series 250A-400A Tech Specs 
• MCCB, Fuji BW Series 500A-600A Tech Specs 
• MCCB, Fuji BW Series 700A-800A Tech Specs 
• MCCB, Eaton 3P Series 15A-100A G-frame Tech Specs 
• MCCB, Eaton 3P Series 60A-225A F-frame Tech Specs 
• MCCB, Eaton 3P Series 250A-400A K-frame Tech Specs 
• MCCB, Eaton 3P Series 400A-600A L-frame Tech Specs 
• MCCB Eaton 3P Series Cross Reference
• Eaton Supplementary Protectors Technical Specs 
• DINnectors Supplementary Protector / Disconnect Tech Specs 
• Edison Fuse Selection Guide Edison Fuse Cross Reference 
• Class CC HCLR Current Limiting Fuses Technical Specs 
• Class CC EDCC Current Limiting Fuses Technical Specs 
• Class CC HCTR Current Limiting Fuses Technical Specs 
• Edison Fuse Holders, EH, EB, EE Series Technical Specs 
• Edison Fuse Holders Comb-Bus Bar Technical Specs 
• Class J Dual Element Time-Delay Fuses Technical Specs 
• Class J High-Speed Drive Fuses Technical Specs 
• Fuse Blocks & Holders, Class J Fuses Technical Specs 
• Class RK5 Dual Element Time-Delay Fuses Technical Specs 
• Class RK1 Dual Element Time-Delay Fuses Technical Specs 
• Class T Extrmely Fast-Acting Fuses Technical Specs 
• Fuse Blocks & Holders, Class T Fuses Technical Specs 
• Midget Class MCL General Purpose Fuses Technical Specs 
• Midget Class MOL General Purpose Fuses Technical Specs 
• Midget Class MEQ General Purpose Fuses Technical Specs 
• Midget Class MEN General Purpose Fuses Technical Specs 
• Edison Fuse Blocks, BC and BM Class Technical Specs 
• Small Dimension Fast-Acting AGC Fuses Technical Specs 
• Small Dimension Fast-Acting ABC Fuses Technical Specs 
• Small Dimension Time-Delay MDL Fuses Technical Specs 
• 5X20mm Glass Fast-Acting GMA Fuses Technical Specs 
• 5X20mm Glass Medium Time-Delay GMC Fuses Technical Specs 
• 5X20mm Fast Fast-Acting S500 Fuses Technical Specs 
• 5X20mm Time-Delay S506 Fuses Technical Specs 
• Small Dimension Time-Delay MDA Fuses Technical Specs 
• GS/DURApulse Fuse Kits Technical Specs 
• DINnector Fused Terminal Block Technical Specs 
• Toggle Switch AC Motor Controllers / Disconnects Specs 
• Enclosed Toggle Switch AC Motor Controllers / Disconnects Specs 
• NEMA 4X Enclosed Rotary Switch AC Motor Controllers Specs 
• CFS Series Compact Fusible Switches Technical Specs 
• UL98 Rated FB Series Fusible Disconnects Selection 
• UL98 Rated FB Series Fusible Disconnects Tech Specs 
• UL98 Rated SC Series Non-Fusible Disconnects Selection 
• UL98 Rated SC Series Non-Fusible Disconnects Tech Specs 
• SD Series Non-Fused Disconnects Technical Specs 
• SD1 & SD2 Disconnects Assembly Instructions 
• SD1 & SD2 Disconnects 6-8 Pole Mounting Instructions 
• SD Series Disconnect Door Interlock Handle Assembly Instructions 

Manuals for Circuit Protection / Fuses / Disconnects

• Fuji MCCB Manual Fuji Electric Molded Case Circuit Breaker Manual
• Eaton MCCB Manual Eaton Corporation Molded Case Circuit Breaker Manual
• FAZ Protector Insert FAZ Series Supplementary Protector Installation Instructions
• Do-more User Manual Do-more T1H PLC User Manual
• Non-Fused Disconnects SD Series Non Fused Disconnects Instruction Sheets
  

Product Inserts for Circuit Protection / Fuses / Disconnects

• WMZS Protector Insert WMZS Series Supplementary Protector Installation Instructions
• Ferraz Disconnect Insert Fuserbloc, Sirco, Gladiator Disconnect Installation Sheet
• Non-Fused Disconnects SD Series Non Fused Disconnects Instruction Sheets
• FAZ Protector Insert FAZ Series Supplementary Protector Installation Instructions
• Motor Controller Insert Manual Motor Controller Toggle Switch Installation Instructions
• WMZT Mini Breaker Insert WMZT Series Mini Circuit Breaker Installation Instructions 
• Crimping Tools Insert Pressmaster Wire Stripping, Cutting and Crimping Tool Instructions
• CFS Disconnects Gladiator CFS Disconnect Switch Installation Instructions
  

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