Fagor DDS Series Hardware Manual page 230

   Power line connection
6.4 Isolating transformer or auto-transformer
6.
238
DDS
HARDWARE
Ref.1912
· 230 ·
When the mains voltage must be isolated or adapted to the levels required
by the DDS system, it may be connected through an isolating transformer or
an auto-transformer. This element will also help reduce the amount of
harmonics on the line although it will not guarantee the compliance with the
CE regulation.
MANDATORY. When installing an isolating transformer, the secondary
must a have a star (Y) configuration with access to the mid point which must
be connected to grond.
The following figure shows the position where the transformer or auto-
transformer must be installed within the whole power line connection
system.
F. H6/2
Position of the auto-transformer or isolating transformer.
MANDATORY. When using transformers or auto-transformers, the main
contactor - KM1 must be connected between them and the DDS system,
never on the input line of the transformer or auto-transformer.
MANDATORY. On machines where the DDS system includes XPS power
supplies, it is essential to properly size the transformer or auto-transformer.
The rated (nominal) power of the auto-transformer is the result from the
Pn=1.4·Pmax
formula , where Pmax is the maximum braking power of the
system. This power may be, in general, close to the power in the S6 duty
cycle of the asynchronous spindle motor. See chapter
CRITERIA .
Hence it is possible to apply simultaneity factors and decrease the power
required by the transformer or auto-transformer.
5. SELECTING