--- title: "MCB, MCCB and HRC fuse comparison" subject: "Industrial Power Distribution and Illumination" chapter: 3 key: "semester_6/industrial_power_distribution_and_illumination:mcb-mccb-hrc-comparison" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/mcb-mccb-hrc-comparison site: BCT Engineering --- # MCB, MCCB and HRC fuse comparison Industrial Power Distribution and Illumination · Chapter 3: Power Carrying Devices - Asked in: 2072 Asoj, 8 marks - Video: [Difference between MCB, MCCB, ELCB, RCCB, RCBO, RCD And MPCB || why we use this device](https://www.youtube.com/watch?v=8VhgQ9Q9ixA) — The Electrical Guy - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/mcb-mccb-hrc-comparison - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-3 ## Question Explain the operating principle of MCB. What are the difference between MCB and MCCB? Compare HRC fuse with MCCB. What is rupturing capacity of MCB, MCCB and HRC fuse? ## Short answer MCB trips via thermal bimetal for overload and magnetic solenoid for short circuit. MCB rated ≤125A, breaking capacity 6-25kA, fixed; MCCB rated up to 2500A, breaking 16-200kA, adjustable. HRC fuse melts, very fast, breaking 80-200kA, must replace; MCCB is reusable, adjustable, can switch. Rupturing capacity: MCB 6-25kA, MCCB 16-200kA, HRC 80-200kA. ## Answer #### Operating principle of MCB An MCB has a **thermal** and a **magnetic** trip acting on a common latch: - **Thermal (overload):** load current heats a bimetal strip; on sustained overload it bends and trips the latch after an inverse-time delay. - **Magnetic (short circuit):** a solenoid in series pulls its plunger instantly when current exceeds a set multiple of rated current (B: 3–5 × In, C: 5–10 × In, D: 10–20 × In), tripping the latch and helping to open the contacts. - The arc is drawn into an **arc chute** of metal plates, split and cooled until it goes out. The MCB is then reset by its lever. #### MCB vs MCCB | Point | MCB | MCCB | |---|---|---| | Current rating | Up to about 100–125 A | About 16 A to 2500 A | | Breaking capacity | 6–10 kA (max about 25 kA) | 16–200 kA | | Trip setting | Fixed | Adjustable (thermal and magnetic) | | Trip unit | Thermal-magnetic | Thermal-magnetic or electronic | | Poles | 1, 2, 3, 4 (DIN rail) | 3 or 4, bolted | | Extras | Few | Shunt trip, under-voltage, aux contacts, motor operator | | Use | Final circuits in buildings | Feeders, motors, main incomers | #### HRC fuse vs MCCB | Point | HRC fuse | MCCB | |---|---|---| | Principle | Melting of silver element in quartz sand | Thermal-magnetic/electronic trip with contacts | | After fault | Must be replaced | Reset and reused | | Speed | Very fast; current limiting | Slower (unless current-limiting type) | | Breaking capacity | 80–120 kA (up to 200 kA) | 16–200 kA | | Adjustability | None | Adjustable settings | | Switching duty | Cannot switch load | Can switch load on/off | | Single phasing | One fuse may blow, motor single-phases | All poles open together | | Cost | Low | High | | Remote operation | Not possible | Possible (shunt trip) | #### Rupturing (breaking) capacity The rupturing capacity is the maximum prospective short-circuit current a device can interrupt safely at rated voltage. Typical values: - **MCB:** 6 kA or 10 kA (IEC 60898), up to about 25 kA. - **MCCB:** 16 kA to about 100 kA, some up to 200 kA (IEC 60947-2). - **HRC fuse:** 80 kA to 120 kA, some up to 200 kA. The device's breaking capacity must be higher than the fault level at the point where it is installed. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which MCB curve trips instantaneously at 10-20 times rated current? A. B curve B. C curve C. D curve D. A curve Answer: C. B is 3-5 In, C is 5-10 In and D is 10-20 In; D suits high inrush loads. (Key point: MCB magnetic curves) 2. Which is true of an MCCB compared with an MCB? A. It has a fixed trip setting and is DIN-rail only B. It is limited to about 125 A C. It has lower breaking capacity but more extras D. It has higher ratings (up to 2500 A), higher breaking capacity and often adjustable trip settings Answer: D. MCCBs are for feeders and motors with adjustable thermal-magnetic or electronic trips. (Key point: MCB vs MCCB) 3. Which is an advantage of an MCCB over an HRC fuse? A. It can be reset and reused, switch load, and open all poles together avoiding single phasing B. It is cheaper and faster, limiting current more C. It has a higher breaking capacity always D. It never needs adjustment or maintenance Answer: A. Fuses must be replaced and may blow in only one phase; MCCBs open all poles and can be remotely tripped. (Key point: HRC vs MCCB) 4. What is rupturing capacity and the rule for selection? A. The maximum continuous load current; it must equal the load B. The maximum prospective short-circuit current a device can interrupt at rated voltage; it must exceed the fault level at the installation point C. The voltage at which it trips; it must equal supply voltage D. The time to clear a fault; it must be below 1 s Answer: B. Breaking capacity must exceed the prospective fault level where the device is installed. (Key point: Rupturing capacity) ## Close variants set in other exams - [Fuse vs MCB and HRC rupturing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Afuse-mcb-hrc-rupturing) — Industrial Power Distribution and Illumination, chapter 3, asked 3× ## Related in Industrial Power Distribution and Illumination - [MCB principle, MCB/MCCB/RCCB, HRC cut-off](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Amcb-mccb-rccb-hrc-cutoff) — Industrial Power Distribution and Illumination, chapter 3 - [Selecting MCCB and MCB for MDB and SDB](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Amccb-mcb-selection-mdb-sdb) — Industrial Power Distribution and Illumination, chapter 5 ## Related in other subjects - [Fuse vs MCB; HRC fuse time terms](https://www.bctengineer.com/question.md?key=semester_6%2Fswitchgear_and_protection%3Afuse-vs-mcb-hrc-terms) — Switchgear and Protection, chapter 3 - [HRC fuse construction; fuse vs MCB](https://www.bctengineer.com/question.md?key=semester_6%2Fswitchgear_and_protection%3Ahrc-fuse-construction-vs-mcb) — Switchgear and Protection, chapter 3 - [HRC fuse operating characteristics and applications](https://www.bctengineer.com/question.md?key=semester_6%2Fswitchgear_and_protection%3Ahrc-fuse-operating-characteristics) — Switchgear and Protection, chapter 3 - [Operating principle of MCB](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_and_electronics_engineering%3Amcb-operating-principle) — Basic Electrical and Electronics Engineering, chapter 4