IS 12640 Part 1 : 1988Miniature circuit-breakers for overcurrent protection for household and similar installations - Part 1: Circuit-breakers for ac operation
Link points to Internet Archive / others. Not hosted by InfraLens. Details
IS 12640:1988 Part 1 is the Indian Standard (BIS) for miniature circuit-breakers for overcurrent protection for household and similar installations - part 1: circuit-breakers for ac operation. This standard specifies requirements for AC miniature circuit-breakers (MCBs) for overcurrent protection in household and similar electrical installations. It covers rated voltages up to 415V AC, rated currents up to 63A, and defines characteristics, construction, performance, and testing methods for Type B, C, and D MCBs.
Specifies requirements for Miniature Circuit Breakers (MCBs) for household and similar installations (still commonly referenced in older specifications).
Overview
Status
Superseded — superseded by IS/IEC 60898 (Part 1):2002
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! This standard has been superseded by IS/IEC 60898-1. All new designs, specifications, and procurement should refer to the latest version of the superseding standard.
! The selection between Type B, C, and D MCBs is critical: 'B' for resistive loads (lighting), 'C' for general purpose/inductive loads (fans, motors), and 'D' for high inrush current loads (transformers).
! The MCB's short-circuit breaking capacity (Icn, e.g., 6kA, 10kA) must be selected to be higher than the prospective fault current at its point of installation.
Electrical accessories - Circuit-breakers for overcurrent protection for household and similar installations - Part 1: Circuit-breakers for a.c. operation
Defines requirements for AC miniature circuit-breakers for non-expert use.
EN 60898-1:2019CENELEC (European)
HighCurrent
Electrical accessories - Circuit-breakers for overcurrent protection for household and similar installations - Part 1: Circuit-breakers for a.c. operation
European adoption of IEC 60898-1, nearly identical in technical requirements.
AS/NZS 60898.1:2022Standards Australia / Standards New Zealand (Australia/New Zealand)
HighCurrent
Electrical accessories - Circuit-breakers for overcurrent protection for household and similar installations, Part 1: Circuit-breakers for a.c. operation (IEC 60898-1:2019, MOD)
Modified adoption of IEC 60898-1 with specific regional deviations.
UL 489UL (US)
LowCurrent
Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures
Covers a broader range of circuit breakers; MCBs fall under 'supplementary protectors' (UL 1077) or branch circuit protection, with different test criteria.
Key Differences
≠IS 12640:1988 is a withdrawn standard, superseded by IS/IEC 60898-1:2015, which is a direct adoption of the IEC standard. The international standard (IEC 60898-1) is current and regularly updated.
≠IS 12640:1988 specified tripping characteristics as Type 'L' series and Type 'G' series. The modern IEC 60898-1 standard specifies tripping curves as Type B, C, and D, which have different instantaneous tripping ranges and are the global norm now.
≠The reference ambient temperature for testing in IS 12640:1988 was 40 °C, reflecting the climatic conditions in India. The standard reference temperature in IEC 60898-1 is 30 °C.
≠The concept of 'Energy Limiting Class' (1, 2, or 3), which specifies the maximum let-through energy during a short circuit, is a mandatory classification and marking in IEC 60898-1. This was not a defined requirement in IS 12640:1988.
Key Similarities
≈Both standards define circuit-breakers intended for the protection of wiring installations in buildings and similar applications against overloads and short-circuits.
≈Both standards cover devices designed to be operated by uninstructed persons and not intended to require maintenance (i.e., 'fit and forget').
≈The fundamental operating principle, combining a thermal element (bimetal) for overload protection and a magnetic element (solenoid) for short-circuit protection, is the basis for devices under both standards.
≈Both standards specify a similar range of preferred rated currents (e.g., 6A, 10A, 16A, 20A, 25A, 32A, 40A, 63A) corresponding to typical final circuit loads.
Parameter Comparison
Parameter
IS Value
International
Source
Standard Status
Withdrawn — superseded by IS/IEC 60898-1:2015
Current (2019 edition)
IEC 60898-1:2019
Tripping Characteristics
Type L (3 to 5 In); Type G (5 to 10 In)
Type B (3 to 5 In); Type C (5 to 10 In); Type D (10 to 20 In)
IEC 60898-1:2019
Reference Ambient Temperature
40 °C
30 °C
IEC 60898-1:2019
Rated Short-Circuit Capacity (Icn)
Preferred values included 3000 A, 6000 A, 9000 A
Standard values include 3000, 4500, 6000, 10000 A
IEC 60898-1:2019
Energy Limiting Class
Not defined
Mandatory classification (Class 1, 2, or 3)
IEC 60898-1:2019
Rated Impulse Withstand Voltage (Uimp)
Not a primary specified parameter
Mandatory requirement, typically 4 kV for distribution boards
IEC 60898-1:2019
Rated Service Short-Circuit Capacity (Ics)
Not explicitly distinguished from Icn
Defined as a percentage of Icn (e.g., 100%, 75%, 50%) to indicate reusability after a fault
IEC 60898-1:2019
⚠ Verify details from original standards before use
Key Values7
Quick Reference Values
Standard rated voltage240/415 V AC
Standard rated currents0.5 A to 63 A
Instantaneous tripping current (Type B)3 to 5 times rated current (In)
Instantaneous tripping current (Type C)5 to 10 times rated current (In)
Instantaneous tripping current (Type D)10 to 20 times rated current (In)
Minimum rated short-circuit capacity (Icn)3000 A (3 kA)
Standard operating temperature-5 °C to +40 °C
Tables & Referenced Sections
Key Tables
Table 1 - Standard values of rated current (In)
Table 2 - Time-current characteristics for type B circuit-breakers
Table 3 - Time-current characteristics for type C circuit-breakers
Table 11 - Test sequence
Key Clauses
Clause 4 - Characteristics of Circuit-Breakers
Clause 6 - Marking
Clause 8 - Constructional and Performance Requirements
No, it has been superseded by IS/IEC 60898-1. This standard is for reference only for older installations.
What is the difference between a Type B and Type C MCB?+
A Type B MCB trips at 3 to 5 times its rated current (In) and is for resistive loads. A Type C MCB trips at 5 to 10 times its rated current (In) and is for general purpose and inductive loads. (Ref: Tables 2 & 3)
What are the standard MCB current ratings as per this code?+
What does the breaking capacity of an MCB signify?+
It is the maximum prospective fault current the MCB can safely interrupt without being damaged. It must be higher than the fault level at the point of installation. (Ref: Clause 4.5)