Medium Voltage Application Guide

SOFT STARTERS
3.5 Selection Guidelines
Considerations
The following information is required to select the starter appropriately. This information is required regardless of
whether you are integrating an IP00 soft starter into a custom-built enclosure or choosing a complete soft starter
panel option.
Operating voltage (U)
Operating current (I)
Expected start current (I STR )
Expected start time (t STR )
Expected stop time (t STP )
Ambient temperature (T A )
Altitude (Alt)
Switchgear requirements
Incoming and motor supply configuration
Customer specific requirements
Operating Voltage, U (kV)
Information IP00 Soft Starter Soft Starter Panel
Operating voltage is the voltage (kV) of the network where the equipment is installed, and is the line voltage applied
across the soft starter's power terminals L1, L2, L3.
The operating voltage will dictate the rated voltage U r (kV) for the equipment to be used.
AuCom solutions are designed to conform to the insulation requirements of IEC 62271-1, where:
the power frequency withstand voltage U d (kV rms, 1 minute) simulates high level voltage surges on the
main supply line at standard frequency;
the rated impulse withstand voltage U p (kV peak) simulates a high level voltage transient induced on the
main supply from a lightning strike. This is a 1.2/50 s transient wave.
IP00
Panel
Rated Voltage
Rated Voltage
U r (kV)
U r (kV)
Operating
Voltage U (kV)
Power
Frequency
withstand U d
(kV rms, 1 min)
Impulse
withstand U p
(kV peak)
Power
Frequency
withstand U d
(kV rms, 1 min)
Impulse
withstand U p
(kV peak)
2.3 2.3 11.5 45
3.3 3.3 11.5 45 4.2 11.5 45
4.2 4.2 11.5 45
6~6.6 6.6 20 45 7.2 20 45
7.2 7.2 20 45
11 12 42 75 12 42 75
Operating Current, I (A)
The maximum operating current (I) of a soft starter installation is the full load current (FLC) of the motor.
The soft starter's rated current I r (A) must be equal to or greater than the motor FLC after considering the following
operating parameters:
I STR expected start current (percentage of motor FLC)
t STR expected start time (seconds)
t STP expected stop time (seconds)
SPH starts per hour
T A ambient temperature (degrees celsius)
Alt installation altitude (metres)
Expected start current and time can be based on typical requirements for a particular load, or can be calculated using
a fully engineered solution. AuCom uses a purpose-designed selection software to select appropriate soft starter
models.
710-12280-00A Medium Voltage Application Guide Page 43