Soft starters prevent torque damage

WEG's new Micro soft starters provide controlled starting and stopping of AC electric motors, overcoming sudden current inrush and high torque problems.

WEG's new Micro soft starters are designed to provide controlled starting and stopping of AC electric motors, overcoming the sudden current inrush and high torque problems which can result in wear and damage to mechanical power transmission equipment, and even to pipe work in pumping applications.

The Micro soft starters are an ideal complement to WEG's market leading range of high efficiency motors.

They provide an extremely simple, low cost and compact solution to the problem of starting AC motors smoothly and efficiently without "snatch".

Designed with fully digital architectures, the soft starters employ the latest digital signal processors (DSPs) to accurately control the ramp voltage supplied to a motor over an optimum time period as set by the user.

This reduces stress on transmission devices, such as gearboxes, shafts and couplings, during motor startup and helps to increase the life of both motor and mechanical parts as mechanical shocks are avoided.

The Micro soft starters also provide high levels of system safeguarding in controlled stopping applications (ramp down), especially where heavy dynamic loads are encountered.

In pumping applications, for example, an extended ramp down time can prevent damage to pipework systems, resulting from the adverse effects of water hammer.

Although extremely compact (the smallest is just 130 x 55 x 145mm) the Micro soft starters offer the user a fully featured package including soft starting/stopping controls, motor protection, metering diagnostics, integrated operator interface pump control and even RS232 serial communications.

This combination of high functionality at low cost means that the units are ideal for OEM applications - especially when employed as part of integrated control systems enclosed in panels.

In these applications, the compact footprint of the soft starters reduces panel space; while simplified wiring and the facility for either direct or DIN rail mounting reduces the time required for installation.

Taken together these factors cut overall installation costs, ensuring improved competitiveness for the OEM panel or machine builder.

Another aid to competitiveness - and general usability - is a simplified operator interface that allows straightforward parameter setting for fast and trouble free start-ups.

No specialist knowledge is required with this interface, programming being accomplished quickly and easily with just four trim potentiometers (for pedestal voltage, acceleration, deceleration times and motor current).

These controls, in common with the five DIP-switches for motor protection, are enclosed behind a hinged door on the fascia of the soft starter, providing a degree of isolation once the switches are set.

A range comprising 24 different models means that the Micro soft starters can cater for the majority of motor starting requirements, in the power range from 0.55 to 55kW.

Conveniently for OEMs, all the models in the range are rated for both 50 and 60Hz operation, with the choice of 13 supply voltages from 220 to 575V (3-85A).

The soft starters meet all the requirements of UL508, for industrial control equipment, IEC60947-4-2 and the European EMC directive 89/336/EEC - industrial environment.

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