Siemens SIRIUS 3RT Series System Manual page 763

Contactor assembly for star-delta (wye-delta) start
Contactor assembly which switches the motor to the star circuit during startup (1/3 of the
starting current compared to delta startup) and back to the delta circuit after a certain period
of time. Contactor assemblies for star-delta (wye-delta) start are used in situations where a
high starting current has to be avoided in order to reduce the effects on the mechanical
components or the line.
Control kit
Tool for closing the main contacts manually by means of the handle.
Coupling module
Function modules consist of at least one basic module, which can be expanded by adding
coupling modules as required. The coupling module includes one NO contact and one 10-
pole connecting cable with a plug connector for insertion into the coupling module and basic
module; it is used for the mutual interlocking of star and delta operation. The communication-
capable version transfers signals to the other contactors and implements the electrical
interlock (reversing/star-delta (wye-delta) start) - in this case, there is no integrated
connecting cable.
Current limiting for soft starters
The SIRIUS 3RW40 soft starter measures the phase current (motor current) continuously
with the help of integrated current transformers. The motor current that flows during the
startup process can be actively limited by means of the soft starter. The current limiting
function takes priority over the voltage ramp function. As soon as a parameterizable current
limit is reached, in other words, the voltage ramp is interrupted and the motor is started with
the current limiting value until it has started up successfully.
The current limiting function is always active with SIRIUS 3RW40 soft starters. If the current
limiting potentiometer is set to the right endstop (maximum), the starting current is limited to
five times the set rated motor current.
The current limiting value is set to the current required during startup as a factor of the rated
motor current. Since the starting current is asymmetrical, the set current corresponds to the
arithmetic mean value for the three phases.
Current monitoring relay
Current monitoring relays are used to monitor motors or other loads for underload and
overload. The level of current permits extensive conclusions to be drawn about the powered
process or plant, e.g. a torn belt, pump no-load operation, tool wear, hoist overload or
blockage. With multi-phase monitoring, the phase sequence, phase failure, or fault current
can be monitored too. If the current measured values are outside the defined range, an alert
will be issued or a disconnection initiated either immediately or with a time delay.
Current setting range (of an overcurrent release)
The range between the lowest and highest current value to which the release can be set.
SIRIUS Innovations
System Manual, 01/2011, A8E56203870002-03
Glossary
763