TECHNICAL CATALOGUE 2012 - AsEG Antriebstechnik GmbH

ElECTRiCal DESigN
connection diaGramS
Windings of standard three-phase single speed motors can be connected either in star
or delta connection.
StAR COnnECtIOn
A star connection is obtained by connecting W2, U2, V2 terminals to eachother and the
U1, V1, W1 terminals to the mains. The phase current and voltage are:
I ph = I n ; U ph = U n / √3
where I n is the line current and U n the line voltage referred to the star connection.
DEltA COnnECtIOn
A delta connection is obtained by connecting the end of a phase to the beginning of
the next phase.
The phase current I ph and the phase voltage U ph are:
I ph = I n / √3 ; U ph = U n
where I n and U n are referred to the delta connection.
U1
U1
W1
V1
W1
V1
W2
U2
V2
W2
U2
V2
U1
V1
W1
U1
V1
W1
L1
L2
L3
L1
L2
L3
Star connection
Delta connection
StAR-DEltA StARtIng
Star-delta starting allows a peak current reduction. It can be used only when the reduced
starting torque obtained is higher than the resistant torque. Actually, it should be noted
that the torque of an induction squirrel-cage motor is directly proportional to the square
of the voltage. Motors whose rated voltage with delta connection corresponds to the
mains voltage, can be started with the star-delta method.
All motors can be supplied with windings designed for star-delta starting (for example:
400 V ∆ / 690 V Y).
36 tHree-PHaSe motorS - TEChNiCal CaTalOguE 1039/12