Motor control systems
From Electrical Installation Guide
Different kinds of motor control solution are compared in the following tables.
| Type | Is/In | Ts/Tn | Speed control | Torque control | Pros | Cons |
|---|---|---|---|---|---|---|
| Direct on line | 5-10 | 5-10 | No | No | Reduced cost, high starting torque | High in-rush current |
| Star – Delta | 2-3 | 1-2 | No | No | Reduced in-rush current | Reduced starting torque |
| Auto-transformer | 2-3 | 1-2 | No | No | Reduced in-rush current | High weight |
| Soft starter | 3-5 | 1.5-2.5 | No | Yes | Reduced in-rush current, controlled start and stop | Reduced starting torque |
| Variable speed drive | 1.5 | 1.5-2 | Yes | Yes | Controlled speed, Energy saving at reduced speed | Higher cost |
Fig. N74 – Comparison of different motor control solutions
