Extreme Operating Conditions: How do I select the right soft starter for extreme conditions?

The published ratings for soft starters assume a particular operating environment. If the soft starter needs to operate outside the assumed conditions, the rating must be revised.

Typical factors include:
- Start current
- Start time
- Start frequency (number of starts per hour)
- Duty cycle
- Ambient temperature
- Altitude

Harmonics: are they an issue for soft start applications?

Harmonics are voltages and currents that create unwanted heating in motors, cables and other equipment. Harmonics can also disrupt operation of electronic equipment.

Harmonic generation by soft starters is insignificant and only occurs during starting or soft stopping. IEC 60947-4-2 (8.3.2.1.1) states “harmonic emissions are of short duration during starting, and there are no significant emissions in the FULL-ON state.

No special actions or filtering are required.

All AuCom soft starters comply with the EMC directive on radiofrequency emissions and immunity.

Non Ventilated Enclosures: What do I need to consider when I install a soft starter in a sealed enclosure?

Soft starters can be installed in sealed enclosures provided the ambient temperature within the enclosure will not exceed the soft starter's rated temperature.

Heat generated within the enclosure must be dissipated, either through the enclosure's walls or by ventilation. When calculating the heat generated in the enclosure, all heat sources must be considered (eg soft starter, fuses, cabling, switchgear etc). The enclosure should be protected form direct sunlight to prevent external heating.
To minimise heating, most soft starters are installed in bypassed configuration.

AuCom’s WinSTART program includes a function to help design enclosure ventilation.