User Manual

Configuration

11.2 Startup class

SIRIUS 3RW30 / 3RW40

Manual, 10/2010, 535199502000 DS 03

11.2 Startup class

To achieve the optimum soft starter design, it is important to know and take into account the

ramp-up time (startup class) of the application. Long ramp-up times mean a higher thermal

load on the thyristors of the soft starter. An appropriately dimensioned SIRIUS 3RW40 or

3RW44 soft starter should be chosen for startup processes with a motor ramp-up time > 20

s. The maximum permissible ramp-up time for SIRIUS 3RW30 soft starters is 20 seconds.

SIRIUS soft starters are designed for continuous operation with normal starting (CLASS 10),

an ambient temperature of 40 °C, and a defined switching frequency (refer to chapter

Technical data (Page 127)). If other data applies, the starters m

ay need to be calculated with

a size allowanc

e. Using the SIEMENS Win-Soft Starter selection and simulation software,

you can enter your application data and requirements to obtain an optimally dimensioned

soft starter (refer to chapter Win-Soft Starter selection and simulation software (Page 169)).

CAUTION

Risk of property damage

When using the 3RW30: Make sure the selected ramp time is longer than the actual motor

ramp-up time. If not, the SIRIUS 3RW30 may be damaged because the internal bypass

contacts close when the set ramp time elapses. If the motor has not finished starting up, an

AC3 current that could damage the bypass contact system will flow.

When using the 3RW40: The 3RW40 has an integrated ramp-up detection function that

prevents this operating state from occurring.

Selection criteria

Note

You must select the size of your SIRIUS soft starters according to the rated motor current

(rated current

soft starter

>= rated motor current).