Technical specifications

Application examples for normal starting (CLASS 10)

¹⁾ The mass inertia of the fan is <10 times the mass inertia of the motor.

Application examples for heavy starting (CLASS 20)

Application examples for very heavy starting (CLASS 30)

¹⁾ The mass inertia of the fan is ≥ 10 times the mass inertia of the motor.

Note:

These tables present sample set values and device dimensions. They are intended for information purposes only and are not binding. The set values depend on the application in question and must be optimized during commissioning.

For dimensioning soft starters under other boundary conditions, also for heavy starting up to CLASS 20, we recommend our Simulation Tool for Soft Starters (STS),
see https://support.industry.siemens.com/cs/ww/en/view/101494917
or contact our Technical Assistance:
Tel.: +49 (911) 895‑5900
Email: technical-assistance@siemens.com.

Circuit concept

The SIRIUS 3RW44 soft starters can be operated in two different types of circuit:

• Inline circuit
  The controls for isolating and protecting the motor are simply connected in series with the soft starter. The motor is connected to the soft starter with three leads.
• Inside-delta circuit
  The wiring is similar to that of wye-delta starters. The phases of the soft starter are connected in series with the individual motor windings. The soft starter then only has to carry the phase current, amounting to about 58% of the rated motor current (conductor current).

Comparison of the types of circuit:

Inline circuit: Rated current I_e corresponds to the rated motor current I_n, three cables to the motor

Inside-delta circuit: Rated current I_e corresponds to approx. 58% of the rated motor current I_n, six cables to the motor (as for wye-delta starters)

Which circuit?

Using the inline circuit involves the lowest wiring outlay. If the soft starter to motor connections are long, this contact sequence is preferable.

The wiring complexity is twice as high when using the inside‑delta circuit, but a smaller device can be used with the same rating. Thanks to the choice of operating mode between the inline circuit and inside‑delta circuit, it is always possible to select the most favorable solution.

The brake function can be used only in the inline circuit.

Configuration

The 3RW44 solid-state soft starters are designed for normal starting. In case of heavy starting or increased starting frequency, a larger unit must be selected.

3RW44 soft starters may be used in isolated supply networks (IT systems) up to 600 V AC.

For long starting times it is recommended to have a PTC sensor in the motor. This also applies for the torque control, pump stop and DC braking ramp-down modes, because during the ramp-down time in these modes, an additional current loading applies in contrast to free ramp-down.

No capacitive elements are permitted in the motor feeder between the SIRIUS 3RW soft starter and the motor (e.g. no reactive-power compensation equipment). In addition, neither static systems for reactive-power compensation nor dynamic PFC (Power Factor Correction) must be operated in parallel during starting and ramp-down of the soft starter. This is important to prevent faults arising on the compensation equipment and/or the soft starter.

All elements of the main circuit (such as fuses and controls) should be dimensioned for direct starting, following the load short-circuit conditions. Fuses and switching devices must be ordered separately.

A bypass contact system and solid-state overload relay are already integrated in the 3RW44 soft starter and therefore do not have to be ordered separately.

The harmonic component load for starting currents must be taken into consideration for the selection of circuit breakers (selection of release).

Note:

When three-phase motors are switched on, voltage drops occur as a rule on starters of all types (direct-on-line starters, wye-delta starters, soft starters). The infeed transformer must always be dimensioned such that the voltage dip when starting the motor remains within the permissible tolerance. If the infeed transformer is dimensioned with only a small margin, it is best for the control voltage to be supplied from a separate circuit (independently of the main voltage) in order to avoid the potential switching off of the soft starter.

For dimensioning soft starters, we recommend our Simulation Tool for Soft Starters (STS),
see https://support.industry.siemens.com/cs/ww/en/view/101494917
or contact our Technical Assistance:
Tel.: +49 (911) 895‑5900
Email: technical-assistance@siemens.com.

Simulation Tool for Soft Starters

The Simulation Tool for Soft Starters (STS) provides a convenient means of designing soft starters using a simple, quick and easy-to-use interface, see "Parameterization, Configuration and Visualization with SIRIUS". Entering the motor and load data will simulate the application and prompt suggestions for suitable soft starters.

Device interface, PROFIBUS DP/PROFINET communication module, SIRIUS Soft Starter ES and SIRIUS Soft Starter ES (TIA Portal) parameterizing and operating software

The solid-state 3RW44 soft starters have a device interface for communicating with the SIRIUS Soft Starter ES and SIRIUS Soft Starter ES (TIA Portal) software or for connecting the external display and operator module. If the optional PROFIBUS/PROFINET communication module is used, the 3RW44 soft starter can be integrated in the PROFIBUS/PROFINET network and can communicate using the GSD file or Soft Starter ES Premium software, see "Parameterization, Configuration and Visualization with SIRIUS".

SIRIUS 3RW44 soft starter Function Block Library for SIMATIC PCS 7

The SIRIUS 3RW44 soft starter PCS 7 block library can be used for simple and easy integration of SIRIUS 3RW44 soft starters into the SIMATIC PCS 7 process control system, see "Parameterization, Configuration and Visualization for SIRIUS". The SIRIUS 3RW44 soft starter PCS 7 block library contains the diagnostics and driver blocks corresponding with the SIMATIC PCS 7 diagnostics and driver concept as well as the elements (symbols and faceplates) required for operator control and process monitoring.