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Electronic motor starters and drives
Basics of drives engineering |
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| Soft Starters (electronic motor start) |
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The characteristic curves for DOL and star-delta starting show current and torque step changes, which have a number of
negative effects, especially at medium and high motor ratings:
- High mechanical machine loads
- Rapid wear
- Increased servicing costs
- High supply costs from the power supply companies (peak current
calculation)
- High mains and generator load
- Voltage dips with a negative effect in other consumers
The ideal scenario of a smooth torque build-up and a controlled current reduction in the starting phase is made possible by the
electronic soft starter. Providing infinitely variable control of the three-phase motor’s supply voltage in the starting phase, it
matches the motor to the load behaviour of the driven machine and accelerates it smoothly. This avoids mechanical jolting and
suppresses current peaks. Soft starters present an electronic alternative to the conventional star-delta switch.
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Features of the soft starters
- For low- to high-power three-phase motors
- No current peaks
- Zero maintenance
- Reduced adjustable starting torque
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