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Compact® NSF and NSJ 150 to 600 A Circuit Breakers
Section 13—Supplementary Technical Information
© 1995–2003 Schneider Electric All Rights Reserved
70
IEC 947-2 TEST PROCEDURE
Standard Tests Consisting of seven parts, the IEC 947 Standard applies to all low-voltage equipment designed for
industrial application.
Three documents are to be consulted for circuit breakers and switches:
• IEC 947-1: general regulations
• IEC 947-2: circuit breakers
• IEC 947-3: switches
Two Categories of
Devices
The IEC 947-1 standard defines two categories of devices:
• Category A—devices not specifically designed to carry out chronometric selectivity
• Category B—devices specifically designed to carry out chronometric selectivity; these circuit
breakers possess a compulsory additional characteristic: short-time withstand (Icw)
Breaking Capacity
Ultimate Breaking
Capacity: Icu
Icu is the value to be taken into account when calculating an installation. The rule remains: Icu > Icc
(maximum fault current of the installation).
Breaking
Performance During
Operation: Ics
This characteristic indicates the ability of the device to eliminate short-circuit currents less than Icc and
with a greater likelihood of occurring, generally near the application. Ics is expressed in % of Icu (values
retained by the standard IEC 25-50-75-100% of Icu). This test sequence designed to check the Ics
performance, groups together on the same device, following the breaking test (O-CO-CO, see page
72), certain checks such as:
• Temperature rise under In
• Calibration at 1.45 In
• Leakage current (for devices suitable for disconnection)
The leakage current should not exceed 2 mA under the application voltage (0.5 mA when new). These
checks ensure that the device is able to carry out all its functions after elimination of a fault of Ics value
and to be put back in operation; hence the notion of breaking power performance during operation Ics.