Product description
3.3 Applications
SIRIUS Innovations - SIRIUS 3RU2 thermal overload relays / SIRIUS 3RB3 solid-state overload relays
22
Manual, 09/2014, A5E03656507420A/RS-AA/002
3.3
Applications
Table 3- 4
Overview of applications
Applications
3RU21
3RB30/3RB31
System protection
✓
1)
✓
1)
Motor protection
✓
✓
Alternating current, 3-phase
✓
✓
Alternating current, 1-phase
✓
-
DC 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. On single-pole
loads, the 3RU21 thermal overload relay or the 3RB22, 3RB23 and 3RB24 solid-state
overload relays for higher applications (no protection for DC loads) must be used for IO-Link.
Reference
More information ...
Can be found in the chapter titled ...
About overload relay applications
Configuration (Page 49)