Soft starters: The modern solution for every girth gear drive

Soft starters replace old mechanical solutions such as star-delta or autotransformers and are gaining market share in the electrical drive field, previously dominated by variable frequency drives. The latest developments in this area was presented at the Middle East Electricity show.

By Andreas Fornwald May 4, 2015

Today’s soft starters have very little in common with the oversized units from the 1980s. A modern medium-voltage soft starter fits into a conventional control panel. This means capacities of up to 4 MW fit into the smallest of spaces or even directly on the application, depending on the requirements. The capacity range is between 200 W and 30 MW. The voltage range is from 220 V up to 15,000 V. With this power range, the soft starter technology covers 99% of the drive assemblies needed on the market. But the development of modern drive assemblies now is subjected to far more stringent demands than the mere capacity range. A holistic view of the installed components and their effects on each other as well as on other system components needs to be taken, particularly in relation to industry norms and standards. The fact that the soft starter has no negative impact on other plant components and thus requires no additional filters and shielded cables facilitates development immensely. 

Start function for pumps

The most recent models have features that provide additional benefits in certain applications. The most common feature is the integrated current limiter, which allows starting the motor with a defined maximum current. This limited power requirement allows a more precise definition of the network load, whereby upstream components such as transformers or generators can be calculated more accurately. Equally widespread is the start function for pump applications, which is due to the fact that it eliminates crucial problems in pumping solutions. Due to the complexity of the respective pipe system, effective solutions cannot be achieved by predetermined ramps but only by an intelligent control system. As a result, the service life of swing check valves is extended and additional components such as automatic valves are saved.

Many users are under the dangerous illusion that every soft starter can reduce the load of a diesel generator. This usually works only up to a certain load. This quickly leads to unstable processes in the generator, which become noticeable through fluctuating voltages and frequencies and can cause the drive assembly to fail. Top soft starters have automatic frequency adjustment that responds to the changed situation of the generator.

The latest developments in soft starter technology were demonstrated at the Middle East Electricity event. The first soft starter was shown with a power level that is completely galvanically isolated from the control level, with inductive transmission technology, increased immunity, and cost-effective design. Because of such technological advancements, modern soft starters have long since fought for and won their place in electrical drive technology.

– Andreas Fornwald is the chief executive officer at IGEL Electric GmbH. Edited by Eric R. Eissler, editor-in-chief, Oil & Gas Engineering,  

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Original content can be found at Oil and Gas Engineering.