Useful terms -Switchgear Nameplate- IEC 60947

While commissioning Assembly, Switchgear Nameplate gives important information, characteristics, Energy, Short Circuit, Accordingly Safety can be ensured.

For ACB / MCCBs :

ParameterSymbolDescription
VoltageUeRated operational voltage
UiRated insulation voltage
UimpRated impulse withstand voltage
CurrentInRated Current
IthConventional free air thermal current
ItheConventional enclosed thermal current
Short CircuitIcmRated short-circuit making capacity
IcuRated ultimate short-circuit breaking capacity
IcsRated service short-circuit breaking capacity
IcwRated short-time withstand current
UtilizationCategory ACircuit Breaker wihout short Time withstand Icw capacity are Calassified as Category A.
Utilization Category A breakers are Current Limiting.
Category BCircuit Breaker with Short Time withstand Icw capacity are Calassified as Category B.
Utilization Category B breakers are Selective (non current limiting)
Trip UnitInRated Current of Breaker
IrANSI 49 – Long time
Adjustable overload setting current
1.05 x IrConventional non-tripping current
1.30 x IrConventional tripping current
trLong time delay setting
IsdANSI 51
Short time delay tripping setting current
tsdShort time delay setting
IiANSI 50
Instantaneous tripping setting current
IgANSI 51N
Earth fault tripping setting current
tgEarth fault time delay setting
IglANSI 51G
Earth Leakage tripping setting current

For MCB :

ParameterSymbolDescription
VoltageUeRated operational voltage
UiRated insulation voltage
UimpRated impulse withstand voltage
CurrentInRated Current
Magnetic trippingB curve4 x In
C curve8 x In
D curve12 x In
UtilizationCategory ACircuit Breaker wihout short Time withstand Icw capacity are Calassified as Category A.
Utilization Category A breakers are Current Limiting.
Limitation class3
B Curve		I2t – A2S, 70000 upto 16Amps
I2t – A2S, 90000 upto 16 to 32Amps
3
C Curve		I2t – A2S, 84000 upto 16Amps
I2t – A2S, 110000 upto 16 to 32Amps
Pollution degree3Conductive and
non-conductive pollution present.
Condensation frequent.
Over Voltage CategoryIVUimp=6KV,
Ue Line to Neultal = 300V
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Factors affecting short circuit fault

Short-Circuit fault allows the current to flow through unintended path with very low impedance, which results into excessive current flow through the path.