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Characteristics of MCB

Created by: Import-User-1 at: 10/24/2011 1:13 PM (5 Replies)

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10/24/2011 1:13 PM	Rate (0)
Import-User-1 Posts: 3609 Rating: (29)	Saran Kumar Dear Friends, I need the answers for the following questions, 1. What are characteristics of MCB & Where it will applicable? 2. Difference b/w above characteristics? (i.e, Diff b/w B-Curve, C-Curve, K,L,M - Curve) Kindly Solve this issue. Regards, Saran
Import-User-1 Posts: 3609 Rating: (29)
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10/25/2011 5:50 AM	Rate (0)
Ayman Elotaify Platinum Member Joined: 5/28/2008 Last visit: 8/31/2025 Posts: 4522 Rating: (843)	Import-User-1 Saran Kumar Dear Friends, I need the answers for the following questions, 1. What are characteristics of MCB & Where it will applicable? 2. Difference b/w above characteristics? (i.e, Diff b/w B-Curve, C-Curve, K,L,M - Curve) Kindly Solve this issue. Regards, Saran Hello Saran, Based on the Tripping Characteristics, MCBs are available in ‘B’,‘C’, ‘D’, 'Z', 'K'and 'S'curve to suit different types of applications. ‘B’ Curve: for protection of electrical circuits with equipment thatdoes not cause surge current (lighting and distribution circuits). Short circuit release is set to (3-5) In ‘C’ Curve: for protection of electrical circuits with equipment thatcauses surge current (inductive loads and motor circuits). Short circuit release is set to (5 - 10) In ‘D’ Curve: for protection of electrical circuits which causes highinrush current, typically 12-15 times the thermal rated current(transformers, X-ray machines etc.). Short circuit release is set to(10 - 20) In ‘K’ Curve: Suitable for applications where high levels of inrush current areexpected. Instantaneous trip is (8 - 12)In. The high magnetic trip point is ideal for motors and transformers. The narrow range (compared with the type D curve) makes itideal for applications where nuisance tripping is not an issue. ‘Z’ Curve: Suitable for applications where semiconductors and other components that fail open are used. Instantaneous trip is (2 - 3)In. The short thermal delay and low magnetictrip point are ideal for applications where devices and componentshave low surge and short circuit tolerances. ‘S’ Curve: Suitable for applications with highly inductive loads, especially incontrol circuits with coils and light filaments. Instantaneous responsebetween (13 - 17) In. Note: If you use the B MCB in place of D curve MCB, chances are the B curve MCB contacts can weld together, or there will be nuisance trippings. On the other hand, if you use a D curve where a B curve MCB has to be used, the system will damage before the breaker can trip. Hope this helps.
	Last edited by: Ayman Elotaify at: 10/25/2011 5:52 AM Ayman Elotaify
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This contribution was helpful to 4 thankful Users AMAZINGAHMED DILIP_1111 Arun Kumar Yadav Chetan2490

10/27/2011 11:18 AM	Rate (0)
Saran Kumar Posts: 2 Rating: (0)	Dear Ayman, Thank you!.... Regards, Saran
Saran Kumar Posts: 2 Rating: (0)
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This contribution was helpful to 1 thankful Users Ayman Elotaify

11/25/2013 8:25 AM	Rate (0)
O_Moderator Diamond Member Joined: 4/24/2009 Last visit: 8/20/2024 Posts: 2682 Rating: (135)	New question splitted to MCBs with Z characteristics? Best regards O_Moderator
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9/2/2025 8:07 AM	Rate (0)
AutoGen_19c6a Joined: 9/2/2025 Last visit: 9/2/2025 Posts: 3 Rating: (0)	Here is the answer for your question: The concept of trip curves originated in the IEC world. The alphabetic code used to categorize miniature circuit breakers (B, C, D, K, and Z) was carried over from IEC standards. The standard defines the lower and upper thresholds for tripping, but manufacturers have the flexibility to decide the precise specifications within those thresholds that will cause a trip in their products. The trip curve graph shows the tolerance band within which manufacturers can set the individual tripping point of their breakers. Various tripping characteristics are therefore available for circuit-breakers, depending on the type of component or equipment to be protected: – B, C, and D for overcurrent protection of cables in accordance with IEC/EN 60898-1 – K for the protecting motors and transformers, and simultaneous overcurrent protection of cables with overload tripping based on IEC/EN 60947-2 – Z for control circuits with high impedances, voltage converter circuits, and semicable protection and simultaneous overcurrent protection of cables with overload tripping based on IEC/EN 60947-2. For more details, you can checkout this article: https://electgo.com/resources/mcb-trip-mcb-connection This articles includes the comparison for each type of mcb tripping curves

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9/2/2025 8:09 AM	Rate (0)
AutoGen_19c6a Joined: 9/2/2025 Last visit: 9/2/2025 Posts: 3 Rating: (0)	MCB - Z characteristics: Tripping range: 2-3 times Typical application: Sensitive electronics, semiconductors Key characteristics: Very sensitive; trips quickly even at small overloads to protect delicate devices I hope it helps. https://electgo.com/resources/mcb-trip-mcb-connection

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