Rockwell Automation Low-Voltage Switchgear and Controlgear - Manual (Page 89)

Mixed star-delta starting
In this case the motor windings are usually divided into two equal halves. On starting, one half
of the part-windings is delta-connected, the other is star-connected (
Fig. 3.3-16 ). The starting
current in star-connection is approx. (2 ... 4) · I
e
. This generates a correspondingly larger
starting torque.
Fig. 3.3-16
Mixed star-delta starting
Circuit diagram and connections of motor coils during starting (Y) and in operation (
∆)
3.3.6 Part-winding star-delta starting
In this case, too, the motor windings are subdivided. In the star connection, only the main
winding – one part of the entire winding – is used (
Fig. 3.3-17 ). The starting current in star
connection is (2 ... 4) · I
e
, depending on tapping, from which a larger breakaway torque results.
LVSAM-WP001A-EN-P - April 2009 3-13