Technical information

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1SDC210033D0202
Glossary
Releases and Protections
G3.1 Release
Device, mechanically connected to a mechanical operating device, which frees the latching
components and allows the operating device to be opened or closed.
G3.2 Thermomagnetic trip unit
Thermomagnetic trip units use a bimetal and an electromagnet to detect respectively over-
loads and short-circuits. They are suitable for protecting both alternating and direct current
networks.
G3.3 Magnetic only trip unit
Device for protection against short-circuits which provides a higher magnetic trip threshold
than the one available with a thermomagnetic circuit-breaker. The magnetic only release
is better able to deal with any problems concerning the particularly high current the motor
absorbs during the first instants of its starting phase.
G3.4 Electronic trip unit
Releases connected to current transformers (three or four, depending on the number of
conductors to be protected) which, installed inside the circuit-breaker, provide the double
function of supplying the power able to operate the release correctly (self-supply) and de-
tecting the value of the current that passes through the live conductors. They are therefore
only compatible with alternating current networks.
The signal from the transformers is processed by the electronic part (microprocessor), which
compares it with the threshold settings. When the signal exceeds the thresholds, circuit-
breaker release is controlled by means of an opening solenoid, which acts directly on the
circuit-breaker control unit.
If there is an auxiliary power supply in addition to self-supply, the voltage value must be
24V DC ±20%.
G3.5 Residual current release
Device able to detect the earth fault current by means of a toroidal transformer which in-
cludes all the live conductors, as well as the neutral if distributed.
Residual current releases can be used in conjunction with the circuit-breaker to obtain two
main functions in one single device:
Q
protection against overloads and short-circuits;
Q
protection against indirect contacts (voltage on conductive parts owing to loss of insula-
tion).
G3.6 Magnetic protection
Protection against short-circuits with instantaneous trip.
G3.7 Thermal protection
Protection against overloads with inverse long-time delayed trip.
G3.8 Protection against Overloads (L)
Protection against overloads with long inverse time delay trip even with the trip curve estab-
lished by the IEC 60255-3 Standard. Used in coordination with fuses and medium voltage
protections.
G3.9 Protection against instantaneous short-circuit (I)
Provides instantaneous protection against short-circuits.
G3.10 Protection against delayed short-circuit (S)
Provides protection against short-circuit currents with delayed intervention at fixed time or
inverse short time. Thanks to the delay setting, this device is particularly suitable when selec-
tive coordination must be achieved among the various different devices.
G3.11 Protection against earth faults (G)
Protection against earth faults with delayed fixed time of trip.
G3.12 Residual current protection (I6n)
This function is particularly suitable when residual current protection is required for protection
against indirect contacts.