Soft Starters in Standard Circuits

The SIRIUS 3RW44 soft starter is connected in the motor branch between the disconnector or circuit breaker and the motor.
The 3RW44 soft starter automatically detects the connection type of the soft starter so this does not have to be explicitly set on the device. The detected connection type can be read on the starter under the menu item "Status display/ Connection type". In this case, the display reads "Star/delta". If the circuitry is faulty or the motor is not connected, the display shows "Unknown"



Soft Starters in Inside Delta Circuits


Prerequisite

A motor whose windings can be connected in a delta circuit where a supply voltage prevails.

Example
Supply voltage: 400 V
Rated motor current: 40.5 A
Current via soft starter in an inside delta circuit approx. 24 A
Selected soft starter in an inside delta circuit 3RW44 22



Figure 3-4:Name plate of a 22 kW motor

The SIRIUS 3RW44 soft starter can be dimensioned to match the current flowing
in the motor section (58 % of the conductor current) by connecting it in the delta winding of the motor. This requires at least 6 motor lines.

The 3RW44 soft starter automatically detects how it is connected so the connection type does not have to be explicitly set on the device. The detected connection type can be read on the starter under the menu item "Status display/ Connection type". In this case the display reads "Inside delta circuit". If the circuitry is faulty or the motor is not connected, the display shows "Unknown".





Protection of the Soft Starter against Short Circuits

The soft starter has integrated thyristor protection against overloading. In the event of a short circuit, e.g. due to a defect in the windings of the motor or auto short-circuit via the motor supply cables, this internal thyristor protection function is not sufficient. Special semiconductor fuses, e.g. SITOR fuses from SIEMENS, must be used for this purpose.