with long-term stability (see Setting the current (rated operational current) and trip class
(Page 81)).
The status "Tripped" is signaled by an "OVERLOAD" LED showing a permanently red light and a
"DEVICE / IO-Link" LED showing a permanently red light. The "OVERLOAD" LED flickers to indicate
an imminent relay trip following violation of a limit current resulting from overload, phase
asymmetry or phase failure. This overload warning is reported as a general warning via the
IO‑Link to the higher-level controller.
If, after a tripping operation, the voltage supply of the overload relay is interrupted within the
recovery time of 3 minutes, the time starts again when the supply is restored, and a period of
3 minutes must elapse before the device is ready for service again.
Thermistor protection
The 3RB24 solid-state overload relays for IO‑Link offer the option of direct temperature
monitoring of the motor windings. Full motor protection is implemented by connection of a cold
conductor (PTC) sensor circuit monitored for short-circuit and wire break.
With this temperature-dependent protection, the loads can be protected against
overtemperature resulting indirectly from restricted coolant flow, for example, and
undetectable by current measurement. In the case of overtemperature, the devices shut down
the contactor and thus the loads via the auxiliary contact.
The status "Tripped" is signaled by a "THERMISTOR" LED showing a permanently red light and a
"DEVICE / IO-Link" LED showing a permanently red light.
Note
To guarantee sure functioning of the short-circuit detection in the thermistor circuit, the line
resistance must not exceed 10 Ω in the case of a short-circuited thermistor.
Ground fault protection
To also protect the loads against high-resistance short circuits due to damage to the insulation,
humidity or condensation the solid-state overload relays for IO‑Link offer the possibility of
internal ground fault detection.
Note
Internal ground fault detection is not possible in conjunction with contactor assemblies for star-
delta (wye-delta) start.
In the event of a ground fault, the relays trip instantaneously.
The "Tripped" status is signaled by means of a "GND FAULT" LED showing a permanently red light
and a "DEVICE / IO-Link" LED showing a permanently red light, and it can also be signaled via IO-
Link.
Ground fault detection can be enabled or parameterized in the solid-state overload relay when
using with motors with 3‑conductor connection (without N connection). Ground fault detection
is disabled in the delivery state.
Product description
3.3 Functions
SIRIUS 3RB24 electronic overload relay for IO-Link
Equipment Manual, 07/2022, NEB969165602000/RS-AA/003
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