Star-delta contactor assemblies

With a star-delta combination that is already assembled in the performance range from 5.5 kW to 90 kW or as individual parts for customer assembly up to a performance class of 500 kW, we offer an affordable, space-saving, and highly available option for reliably starting asynchronous motors.

Star-delta contactor assemblies portfolio


Performance range up to 90 kW

SIRIUS 3RA24 contactor assemblies for star-delta (wye-delta) starting, up to 90 kW

The 3RA24 contactor assemblies for star-delta (wye-delta) starting in sizes S00 to S3 can be ordered as follows:

  • Fully wired and tested, with electrical and mechanical interlock

Benefits of preassembled star-delta combinations

  • Space-saving
  • Different connection technologies: screw terminals, spring-type terminals
  • Only one order number

Customer assembly

Performance range 5,5 kW -  500 kW

Star-delta combinations for customer assembly

Naturally, we also offer you the option of ordering and assembling individual contactors in different performance classes from 5.5 kW to an output of 500 kW for star-delta combinations. As of a desired output of over 90 kW, the combinations of individual products must be assembled by the customer.


Flyer: Product selection for self-assembly of classic star-delta (wye-delta) starters up to 90 kW, normal starting Class 10

Highlights at a glance

Preferred circuitry 

A star-delta (wye-delta) circuit reduces the starting current to 1/3 of the current compared to the current values for direct-on-line starting. However, when switching over from the star connection to the delta connection, the motor may be subjected to compensation processes, reinforced by an unfavorable constellation of line frequency and rotor field, which could result in higher current peaks than would be the case if the stationary motor were connected directly in the delta circuit.


An unfavorable scenario could lead to the following problems:

• Tripping of short-circuit protection devices,
• Welding or substantial contact erosion of the delta contactor,

• High dynamic load on the motor.


When connecting the motor using the preferred circuitry, the switchover currents from the star to the delta connection can be reduced.
This can avoid the problems mentioned above. 

Downloads, Tools and Support for Star-delta contactor assemblies

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