Features Of Overload Relays - Siemens SIRIUS 3RT Series System Manual

SIRIUS 3RU2/3RB3 overload relays
5.10 Technical data
5.10.1.5

Features of overload relays

Table 5- 37 Other characteristics of 3RU21 and 3RB30/3RB31 overload relays
Feature
Temperature compensation
High long-term stability
Wide setting ranges
Tripping class CLASS 5
Tripping class > CLASS 10
Low power loss
Intrinsic supply
Variable setting of tripping classes
(The required tripping class can be
set dependent upon the prevailing
starting conditions using a rotary
switch.)
As SIRIUS 3RU21 thermal overload relays work on the basis of the bimetal principle, they
1)
do not require a control supply voltage.
538
Description
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

Provides reliable protection of loads even after

years under severe operating conditions
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
Enables solutions for motors which start up very

quickly and require special protection measures
Enable solutions for heavy-duty starting

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)
Eliminates the need for configuration and

connecting an additional control circuit
Reduces the number of variants

Minimizes the engineering outlay and costs

Enables savings to be made where storage

overheads, storage costs, and tied-up capital are
concerned
3RU21
✓
✓
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--
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--
1)
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SIRIUS Innovations
System Manual, 01/2011, A8E56203870002-03
3RB30/3RB
31
✓
✓
✓
(1:4)
✓
(3RB31
only)
✓
✓
✓
✓
(3RB31
only)