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Description
2.8 Electronic trip unit
ETU protection against overtemperature
The ETUs are equipped with a temperature sensor for their own protection. This effectively
protects the electronic components of the ETU against irreparable damage.
This protection takes effect in two stages:
● The first stage is an alarm which is indicated by LEDs directly on the ETU. This alarm is
activated when the temperature reaches 90% of the maximum permissible temperature. It
is automatically reset when the temperature falls below the activation limit.
With 5-series and 8-series ETUs, this alarm can also be transmitted to a higher-level
control system via the communication system.
● The second stage immediately opens the 3VA2 molded case circuit breaker when the
maximum permissible temperature is exceeded in the ETU.
The molded case circuit breaker cannot be switched back on until the temperature falls
below approx. 95% of the maximum permissible temperature.
The temperature values of this temperature sensor do not allow any conclusions to be drawn
about the temperature changes of other components within the circuit breaker, e.g. the
circuits.
Note
The customer may perform insulation tests on the main circuits and the neutral conductor
with test voltages up to 4 kV DC and surge voltages up to 14.5 kV.
88
3VA molded case circuit breakers with IEC certificate
Manual, 03/2019, A5E03603177010-03
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