Danfoss Drives · DKDD.PB.551.A1.02 | 25
Inside delta Connection:
What is “inside delta” connection?
With inside delta (six wire connection), the soft starter SCRs are in
series with each motor winding so that the soft starter carries only
phase current, not line current. The soft starter can thus control a
motor with greater full load current than normal.
Inside delta connection is only possible with motors that allow
each end of all three motor windings to be connected separately,
and not all soft starters can be connected using inside delta. A line
contactor or shunt trip MCCB must always be used to disconnect
the motor and soft starter from the supply in the event of a trip.
Inside delta connection simplies replacement of star/delta starters
because the existing wiring can be used. In new installations,
inside delta connection may reduce the size and cost of the soft
starter, but there are additional costs for the line contactor/shunt
trip MCCB and extra cabling.
MCD 200 soft starters cannot be installed using
inside delta connection.
MCD 500 soft starters have built-in support for
inside delta connection.
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