Siemens SIRIUS 3RU - Features of Overload Relays

Technical data
11.3 Performance features
SIRIUS 3RU thermal overload relays / SIRIUS 3RB electronic overload relays
Manual, 09/2016, A5E03656507420A/RS-AB/003
151
11.3.4
Features of overload relays
Table 11- 4 Additional characteristics of 3RU21 thermal overload relays and 3RB20 / 3RB21 and 3RB30 / 3RB31
electronic overload relays
Feature
Description
3RU21
3RB20 / 3RB21
3RB30 / 3RB31
Temperature compensation
• Allows the use of the relays without derating even
at high temperatures
• Prevents premature tripping
• Allows compact control cabinet installation without
clearance between the devices/load feeders
• Simplifies configuration
• Enables space to be saved in the control cabinet
✓ ✓
High long-term stability
• Provides reliable protection of loads even after
years under severe operating conditions
✓ ✓
Wide setting ranges
• Reduce the number of variants
• Minimize the engineering outlay and costs
• Enable savings to be made where storage
overheads, storage costs, and tied-up capital are
concerned
-- ✓
(1:4)
Variable setting of tripping
classes
(The required tripping class can
be set dependent upon the
prevailing starting conditions
using a rotary switch.)
• Reduces the number of versions
• Minimizes the configuring outlay and costs
• Minimizes storage overhead, storage costs, and
tied-up capital
-- ✓
(3RB21 / 3RB3
1 only)
Tripping class CLASS 5E
• Enables solutions for motors which start up very
quickly and require special protection measures
-- ✓
(3RB21 / 3RB3
1 only)
Tripping class > CLASS 10E
• Enable solutions for heavy-duty starting
-- ✓
Low power loss
• Reduces power consumption (power consumption
is up to 98% less than with thermal overload relays)
and thus energy costs
• Minimizes the temperature rise of the contactor and
the control cabinet - in some cases this may
eliminate the need for control cabinet cooling
• Enables space to be saved through direct mounting
on the contactor even at high motor currents (i.e.
no heat decoupling is required)
-- ✓
Intrinsic supply
• Eliminates the need for configuration and
connecting an additional control circuit
--
1)
✓
1)
As SIRIUS 3RU21 thermal overload relays work on the basis of the bimetal principle, they
do not require a control supply voltage.