SIEMENS
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Siemens IC 10 · 2017
Power Contactors for Switching Motors
SIRIUS 3RT12 and 3TF6 vacuum contactors
3
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Overview
Vacuum contactors
Standards
IEC 60947-1, EN 60947-1,
IEC 60947-4-1, EN 60947-4-1,
IEC 60947-5-1, EN 60947-5-1 (auxiliary switches)
The SIRIUS 3RT12 and 3TF68/3TF69 vacuum contactors are
suitable for use in any climate. They are finger-safe according to
IEC 60529. Terminal covers may have to be fitted onto the con-
necting bars, depending on the configuration with other devices
(see pages 3/116 and 3/138)
.
Connection methods
The vacuum contactors are available with screw terminals
(box terminals).
Contact reliability
If voltages
110 V and currents
100 mA are to be switched,
the auxiliary contacts of the vacuum contactors or 3RH contac-
tor relays should be used as they guarantee a high level of
contact reliability.
These auxiliary contacts are particularly suitable for solid-state
circuits with currents
1 mA at a voltage
17 V.
Short-circuit protection
For short-circuit protection of vacuum contactors without
overload relays,
see "Technical specifications", page 3/129
.
For short-circuit protection of vacuum contactors with overload
relays,
see the Configuration Manual "Configuring SIRIUS –
Selection Data for Fuseless Load Feeders",
.
Electromagnetic compatibility (EMC)
The contactors with solid-state operating mechanism comply
with the international standards IEC/EN 60947-1 and
IEC/EN 60947-4-1.
These contactors have been developed for environment A.
Note:
Environment A refers to private low-voltage or industrial net-
works/locations/plants, including high-grade sources of interfer-
ence.
Environment A corresponds to devices of Class A with
CISPR 11, EN 55011.
Note:
In connection with converters, the control cables must be routed
separately from the load cables to the converter.
Motor protection
For protection against overload, 3RB2 electronic overload relays
(see page 7/109 onwards)
can be mounted on the vacuum con-
tactors. These must be ordered separately.
Ratings of three-phase motors
The quoted rating (in kW) refers to the output power on the motor
shaft (according to the nameplate).
The power rating specifications of the vacuum contactors in kW
are guide values for 4-pole standard motors at 50 Hz AC and
specified voltage (e.g. 400 V). The actual starting and rated data
of the motor to be switched must be considered when selecting
the units.
Surge suppression
The vacuum contactors can be retrofitted with varistors for
damping opening overvoltages in the coil.
Note:
The OFF-delay of the NO contact and the ON-delay of the
NC contact are increased if the contactor coils are attenuated
against voltage peaks (varistor +2 to 5 ms)
Vacuum contactors are basically unsuitable for switching
DC voltage.
SIRIUS 3RT12 vacuum contactors, 3-pole, 110 to 250 kW
AC/DC operation
The contactors can be operated with AC (50 to 60
Hz) as well as
with DC.
Two types of solenoid operation are available:
•
Conventional operating mechanism, version 3RT12. .-.A
•
Solid-state operating mechanism, version 3RT12. .-.N
Withdrawable coils
For simple coil replacement, e. g. if the application is replaced,
the solenoid coil can be pulled out upwards after the release
mechanism has been actuated and can be replaced by any
other coil of the same size.
Vacuum interrupters
In contrast to the 3RT10 contactors – the main contacts operate
in air under atmospheric conditions – the contact gaps of the
3RT12 vacuum contactors are contained in hermetically en-
closed vacuum interrupters. Neither arcs nor arcing gases are
produced. The particular benefit of 3RT12 vacuum contactors,
however, is that their electrical endurance is at least twice as
long as that of 3RT10 contactors. They are therefore particularly
well suited to frequent switching in inching/mixed operation, e.g.
in crane control systems.
Auxiliary contact complement
The 3RT12 vacuum contactors of sizes S10 to S12 are supplied
with laterally mounted auxiliary switch blocks. These can be fit-
ted with up to eight lateral auxiliary contacts (identical auxiliary
switch blocks for S10 and S12). Of these, no more than four are
permitted to be NC contacts.
3TF6 vacuum contactors, 3-pole, 335 to 450 kW
Main contacts
Contact erosion indication with 3TF68/3TF69 vacuum
contactors:
The contact erosion of the vacuum interrupters can be checked
during operation with the help of three white double slides on the
contactor base. If the distance indicated by one of the double
slides is < 0.5 mm while the contactor is in the closed position,
the vacuum interrupter must be replaced. To ensure maximum
reliability, it is recommended to replace all three vacuum inter-
rupters simultaneously.
Auxiliary contacts
Contact reliability:
These auxiliary contacts are particularly suitable for solid-state
circuits with currents
1 mA at a voltage
17 V.
Protection of the main current paths
An integrated RC varistor connection for the main current paths
dampens the switching overvoltage rises to safe values. This
prevents multiple restricting. It can therefore be assumed that
the motor winding cannot be damaged by switching overvolt-
ages with steep voltage rises.
During operation in installations in which the emitted interference
limits cannot be observed, e.
g. when used for output contactors
in converters, 3TF68/3TF69..-.
Q
vacuum contactors – without
connection of the main current path circuit – are recommended.
© Siemens AG 2016