Overview

Overview

Boundary conditions

The motor ratings listed in the Selection and ordering data are rough guide values. The soft starter should always be designed on the basis of the required rated operational current of the motor. 3RW soft starters are designed for easy starting conditions.

For selection of soft starters in the Selection and ordering data, a current load of 300% was defined for all 3RW soft starters as the boundary condition for normal starting (CLASS 10). For 3RW30, a maximum number of 20 starts per hour for a maximum of 3 s starting time was defined as the boundary condition; for 3RW40 and 3RW44, a maximum number of five starts per hour for a maximum starting time of 10 s was defined.

In case of additional requirements, it may be necessary to choose a larger device. In some cases, however, the safety margins taken into account in the selection also permit the listed units to be used in boundary conditions which are slightly more demanding.

We generally recommend the Simulation Tool for Soft Starters (STS) for selection of 3RW soft starters. See https://support.industry.siemens.com/cs/ww/en/view/101494917.

Motor rating data in kW and hp is based on IEC 60947‑4‑1.

Article No. scheme

Note:

The Article No. scheme shows an overview of product versions for better understanding of the logic behind the article numbers.

For your orders please use the article numbers quoted in the selection and ordering data.