Specifications

58
COMPACT
®
NS circuit breaker
COMPACT
®
NS circuit breaker: supplementary technical information
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.
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).
Two categories of devices
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 59), 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.
Function
Recognition and definition of the disconnection
capacity for industrial low-voltage equipment
Until recently, circuit breaker standards have
established no regulations concerning the isolation
function.
Only the installation standards provided some rather
vague information.
The IEC 947 standard takes this function into account.
In the "general regulations" section, it clearly states:
❑ The manufacturing regulation,
❑ The tests to be performed.
The circuit breaker standard should define the manner
in which the tests are to be performed (under study).
The manufacturing regulations state, for example:
❑ Both the isolation and the inner contact distances
(open > 8 mm),
❑ A device indicating the true position of the contacts
(operating handle if representative of the state of all
the contacts),
❑ When a "locked" position is provided, this should
only be possible with "open" contacts.
Isolation
E29235
The tests to be performed are as follow:
■ Shock wave voltage strength (Uimp)
1.2/50 µs - 12.3 kV plus 25% between open contacts in comparison with devices not
fitted with the applied isolation function according to the figure below.
The test is validated if no triggering occurs between the contacts.
■ Measurement of the leakage current
Under 110% of the device application voltage
❑ Maximum leakage currents proposed per pole:
– 0.5 mA new device,
– 2 mA device after Ics,
– 6 mA device after Icu or after endurance tests, representative of the "end of
service life."
0 t1 t2
0.1
0.5
0.9
U
1.2 50
V
tµs
12.3 kV
Uimp