Why Use a Soft Start?

A soft starter is an additional device that can be added to a typical AC electric motor that will allow the motor to use a different startup method. The purpose of this device is to reduce the strain put on the motor during the typical power-up phase of a motor. A soft starter is used to reduce the inrush currents and limit torque, useful if you want to protect your equipment, extend the life of your motor and reduce motor heating with frequent starts and stops. So, a soft starter provides a gentle acceleration up to full speed and they are used only at startup.

Are you experiencing mechanical or electrical problems?

The financial consequences are considerable; every technical problem and every breakdown costs money in terms of repairs as well as lost production.

Electrical problems due to voltage and current transient arising from Direct-On-Line or Star-Delta starts. Such transients may overload the local supply network and cause unacceptable voltage variations that interfere with other electrical equipment connected to the network.

Mechanical problems that address the entire drive chain, from motor to driven equipment, causing a big need for service and repair as well as unwanted down time.

ABB PSTX Soft Starter

Operational problems, such as damage to products on conveyor belts.

Water hammering and pressure surges in pipe systems when starting and stopping pumps.

The easy solution to all of these problems is to install an ABB Softstarter type PSR, PSS, PSE or PST(B). With ABB Softstarters, it is possible to start and stop smoothly while keeping mechanical and electrical stresses to a minimum.

Differences between different starting methods

Different Starting Methods

Graphs showing the basic differences between Direct-On-Line starting (DOL),
star-delta starting and soft starting in terms of the motor voltage (U), motor current (I) and motor torque (T).


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