Automation Direct Stellar SR55 Series - SR55 Soft Starter Selection Steps

Page D–2 Stellar
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SR55 Series Soft Starter User Manual – 1st Ed, Rev F – 09/18/2019
Appendix D: Sizing an SR55 Soft Starter
sR55 sofT sTARTeR selecTIoN sTeps
1) Determine the required trip class based on the motor load and required start time. See
O/L Trip Classes table below. (Also refer to the definitions of Class 10, 20, and 30 Trip
Curves in the “SR55 Soft Starter Overload Trip” section of this chapter.)
SR55 Soft Starters – O/L Trip Classes
Default 10 Crusher 30 Pump - Submersible Centrifugal 10
Heavy 20 Fan - Low Inertia <85A 10 Pump - Submersible Rotodynamic 10
Agitator 10 Fan - High Inertia >85A 30 Pump - Positive Displacement Reciprocating 20
Compressor - Centrifugal 20 Feeder - screw 10 Pump - Positive Displacement Rotary 20
Compressor - Reciprocating 20 Grinder 20 Pump Jack 20
Compressor - Rotary Screw 20 Hammer mill 20 Rolling mill 20
Compressor - Rotary Vane 10 Lathe machines 10 Roots Blower 20
Compressor - Scroll 10 Mills - Flour, etc. 20 Saw - Band 10
Ball mill 20 Mixer - Unloaded 10 Saw - Circular 20
Centrifuge* 30 Mixer - Loaded 20 Screen - Vibrating 20
Bow Thruster - Zero Pitch 10 Molding Machine 10 Shredder 30
Bow Thruster - Loaded 20 Pelletizers 20 Transformers, Voltage Regulators 10
Conveyor - Unloaded 10 Plastic and textile machines 10 Tumblers 20
Conveyor - Loaded 20 Press, flywheel 20 Wood chipper 30
* Size centrifuge starter at I(A) = (motor FLA x 2.3). Trip Class 30.
2) From the SR55 Soft Starters Selection Table below, select the row with the correct motor
full load amps. Then select the correct SR55 soft starter based on Trip Class (longer
start times require a larger starter). Notice that there are different Motor Amps columns
for starters wired In-Line (most common) and In-Delta. Select the applicable SR55 part
number based on the required Trip Class, motor HP, and connection type.
SR55 Soft Starters – Selection Table (per IEC 60947-4-1:2009 Table G.1)
Motor Size Soft Starter Size
In-Line Connection In-Delta Connection * Application Trip Class
I (A)
HP @
I (A)
HP @
Class 10 Class 20 Class 30
200V 208V 230V 460V 200V 208V 230V 460V
17 3 5 5 10 29 7.5 7.5 10 20 SR55-017 SR55-021 SR55-027
21 5 5 5 15 36 10 10 10 25 SR55-021 SR55-027 SR55-034
27 7.5 7.5 7.5 20 47 10 15 15 30 SR55-027 SR55-034 SR55-040
34 10 10 10 25 59 15 15 20 40 SR55-034 SR55-040 SR55-052
40 10 10 10 30 69 20 20 25 50 SR55-040 SR55-052 SR55-065
52 15 15 15 40 90 25 30 30 60 SR55-052 SR55-065 SR55-077
65 20 20 20 50 113 30 30 40 75 SR55-065 SR55-077 SR55-096
77 20 25 25 60 133 40 40 50 100 SR55-077 SR55-096 SR55-124
96 30 30 30 75 166 50 50 60 125 SR55-096 SR55-124 SR55-156
124 40 40 40 100 215 60 75 75 150 SR55-124 SR55-156 SR55-180
156 50 50 60 125 270 75 75 100 200 SR55-156 SR55-180 SR55-242
180 60 60 60 150 312 100 100 125 250 SR55-180 SR55-242 SR55-302
242 75 75 75 200 419 150 150 150 300 SR55-242 SR55-302 SR55-361
302 100 100 100 250 523 150 150 200 450 SR55-302 SR55-361 SR55-414
361 125 125 150 300 625 200 200 250 500 SR55-361 SR55-414 SR55-477
414 150 150 150 350 717 250 250 250 500 SR55-414 SR55-477 n/a
477 150 150 150 400 826 250 300 300 600 SR55-477 n/a n/a
* For In-Delta connections, all six motor wires must be available for connection, and it is critical to exactly follow
the In-Delta wiring diagram in the SR55 User Manual or Quick-start Guide. Nine-lead motors CANNOT be
connected in the delta. The Soft Starter will only sense the Phase Current, which is about 58% of the Line
Current.
* For In-Delta connections, a main contactor that is controlled by the Run relay of the SR55 must be used in the
incoming power circuit for isolation. Circuit breaker isolation alone is not sufficient.
* iERS energy optimizing feature is not available for In-Delta connections.