SIRIUS 3RU2/3RB3 overload relays
5.2 Product description
SIRIUS Innovations
488 System Manual, 01/2011, A8E56203870002-03
5.2.3 Applications
Table 5- 3 Overview of applications
Applications 3RU21 3RB30/3RB31
System protection ✓
1)
✓
1)
Motor protection ✓ ✓
Alternating current, 3-phase ✓ ✓
Alternating current, 1-phase ✓ -
Direct current ✓ -
1)
In the main circuit, the devices provide overload protection for the assigned electrical loads (e.g.
motors), feeder cable, and other switching and protection devices in the respective load feeder.
The 3 phases have to be under symmetrical load.
3RU21 thermal overload relays
3RU21 thermal overload relays have been designed to protect three-phase loads, DC loads,
and single-phase AC loads.
Note
Protection of DC loads/single-phase AC loads
If a 3RU21 thermal overload relay is to be used to protect DC loads or single-phase AC
loads, all the bimetal strips have to be heated. Therefore, all of the relay's main current paths
have to be connected in series.
3RB30/3RB31 solid-state overload relays
3RB30/3RB31 solid-state overload relays are designed to protect three-phase loads in
sinusoidal 50/60 Hz voltage supplies.
Note
DC loads/Single-phase AC loads
The relay is not suitable for protecting DC loads or single-phase AC loads. In the case of
loads with single-pole load, the 3RU21 thermal overload relay or the 3RB22/3RB23 solid-
state overload relay (only suitable for the protection of single-phase AC loads) should be
used.
Reference
More information ... Can be found in the chapter titled ...
About overload relay applications Configuration (Page 503)
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