Soft Start Trip Class Guidance
This guide provides general recommendations for selecting the correct trip class for a soft starter. Careful selection is essential to ensure the starter can meet the demands of the application, as different loads have different starting characteristics.
Useful Information:
- All soft starters on inverterdrive.com are listed using Trip Class 10 ratings to allow easy comparison. Alternative ratings and trip classes are shown within each product listing.
- We display in-line ratings as standard to avoid confusion. Where available, inside-delta ratings can be found in the product filters.
What is Trip Class?
Trip class defines how long a motor can sustain a starting current before the soft starter trips on overload. Higher trip classes allow longer start times, which are typically required for high inertia or heavily loaded applications.
Trip Class Guide
Common applications are shown below as a general guide to selecting an appropriate trip class when choosing a soft starter.
Soft Starter Trip Class Selection Guide
| Application |
Typical Trip Class |
Start Time (secs) |
Notes |
| Default |
10 |
10 |
|
| Fan (Low Inertia) |
10 |
15 |
Generally 37kW and less |
| Fan (High Inertia) |
30 |
10 |
Generally 45kW and above |
| Conveyor (Unloaded) |
10 |
7 |
Starts with no load |
| Conveyor (Loaded) |
20 |
7 |
Starts with load |
| Compressor (Vane) |
10 |
7 |
Also suitable for scroll compressors |
| Compressor (Reciprocating) |
20 |
15 |
Also suitable for centrifugal compressors |
| Pump (Centrifugal) |
10 |
10 |
Submersible type |
| Pump (Positive Displacement) |
20 |
10 |
Reciprocating and rotary |
| Crusher |
30 |
10 |
Can be difficult to start loaded |
| Shredder |
30 |
10 |
Can be difficult to start loaded |
| Feeder (Screw) |
10 |
10 |
Also suitable for band saws |
Table from Motortronics Ltd reproduced March 2025 by The Inverter Drive Supermarket.