Inside-Delta Circuit - Siemens SIRIUS 3RW55 Equipment Manual

Feeder assembly
You must provide protection for all power semiconductors against short circuits by means of
special semiconductor fuses (e.g. SITOR fuses from Siemens) to achieve coordination type 2. A
short circuit can occur, for instance, as a result of a defect in the motor windings or in the motor's
power supply cable.
Q1
F3
F3*
Q11
M1
PE
A.1.4

Inside-delta circuit

If the 3RW55 or 3RW55 Failsafe soft starter is operated in an inside-delta circuit, the motor power
output of the individual devices is increased by a factor of root 3.
SIRIUS 3RW55 and 3RW55 Failsafe Soft Starters
Equipment Manual, 02/2022, A5E35630887002A/RS-AF/006
Motor starter protector
aR partial-range fuse for protection of semiconductors (e.g. SITOR 3NE3/4 or 3NC3)
gR full-range fuse for protection of semiconductors (e.g. SITOR 3NE1)
3RW55 or 3RW55 Failsafe soft starter
Motor
Protective conductor
Example circuits
A.1 Main circuit connection
295