SIEMENS
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Siemens IC 10 · 2017
Solid-State Switching Devices for Resistive/Inductive Loads
Solid-State Contactors
General data
6
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Overview
Solid-state contactors (with integrated heat sink)
The complete units consist of a solid-state relay plus optimized
heat sink, and are therefore ready to use. They offer defined
rated currents to make selection as easy as possible.
Depending on the version, current intensities of up to 70 A are
achieved. Like all of our solid-state switching devices, one of
their particular advantages is their compact and space-saving
design.
With their insulated mounting foot they can easily be snapped
onto a standard mounting rail, or they can be mounted on
support plates with fixing screws. This insulation enables them
to be used in circuits with protective extra-low voltage (PELV) or
safety extra-low voltage (SELV) in building management
systems. For other applications, such as for extended personal
safety, the heat sink can be grounded through a screw terminal.
The solid-state contactors are available in 2 different versions:
• 3RF23 single-phase solid-state contactors
• 3RF24 three-phase solid-state contactors
Single-phase versions
The 3RF23 solid-state contactors can be expanded with various
function modules to adapt them to individual applications.
Version for resistive loads "zero-point switching"
This standard version is often used for switching space heaters
on and off.
Version for inductive loads "instantaneous switching"
In this version the solid-state contactor is specifically matched to
inductive loads. Whether it is a matter of frequent actuation of the
valves in a filling plant or starting and stopping small operating
mechanisms in packet distribution systems, operation is carried
out safely and noiselessly.
Special "Low noise" version
Thanks to a special control circuit, this special version can be
used in public networks up to 16 A without any additional
measures such as interference suppressor filters. As a result, in
terms of emitted interference, it conforms to limit value curve
class B according to IEC 60947-4-3.
Special "Short-circuit proof" version
Skillful matching of the power semiconductor with the
performance capacity of the solid-state contactor means that
"short-circuit strength" can be achieved with a standard
miniature circuit breaker. In combination with a B-type MCB or a
conventional line protection fuse, the result is a short-circuit
proof feeder.
In order to achieve problem-free short-circuit protection by
means of miniature circuit breakers, however, certain boundary
conditions must be observed. As the magnitude and duration of
the short-circuit current are determined not only by the short-
circuit breaking response of the miniature circuit breaker but
also the properties of the wiring system, such as the internal
resistance of the input to the network and damping by controls
and cables, particular attention must also be paid to these
parameters. The necessary cable lengths are therefore shown
for the main factor, the line resistance, in the table below.
The following miniature circuit breakers with a B characteristic
and 10 kA or 6 kA breaking capacity protect the 3RF23..-.DA..
solid-state contactors in the event of short circuits on the load
and the specified conductor cross-sections and lengths:
1)
The miniature circuit breakers can be used up to a maximum rated voltage
of 480 V!
Solid-state contactor protection
The setup and installation above can also be used for the solid-
state relays with an
I
2
t
value of at least 6600 A
2
s.
3-phase versions
The three-phase solid-state contactors for resistive loads up to
50 A are available with
•Two-phase control (suitable in particular for circuits without
connection to the neutral conductor) and
•Three-phase control (suitable for star circuits with connection
to the neutral conductor or for applications in which the system
requires all phases to be switched)
The converter function module can be snapped onto both
versions for the simple power control of AC loads by means of
analog signals.
•Check the correct contactor size with the aid of the rated
current diagram, taking account of the installation conditions
Rated current of the
miniature circuit
breaker
Example of
type
1)
Max. conductor
cross section
Minimum cable
length from
contactor to
load
6 A
5SY4106-6
1 mm
2
5 m
10 A
5SY4110-6
1.5 mm
2
8 m
16 A
5SY4116-6
1.5 mm
2
12 m
2.5 mm
2
20 m
20 A
5SY4120-6
2.5 mm
2
20 m
25 A
5SY4125-6
2.5 mm
2
26 m
NSB0_01473b
K1
L2
L1
L
1
L3
N
2
T
F1
I,A
R1
F2
K1
L2
L1
L
1
L3
N
2
T
F1
I,A
R1
line
3/N/PE
50 Hz 230/400 V
3/N/PE
50 Hz 230/400 V
line
line
© Siemens AG 2016