Ahead of the October issue article on conveyors comes important news from ABB. The start-up of drive systems using slip-ring motors, e.g. belt conveyors or crushers places heavy loads on gears and couplings. Recently ABB introduced an electronic soft start system – ECOSS – for slip-ring drives. Conveyor belts often require a starting torque very close to or even above the nominal torque of the motor. Generally, a constant load torque applies which depends on the belt load and lift required. The electronic starter ECOSS enables a controlled start-up which puts less stress on the components.

The starter works according to the principle of rectification and subsequent modulation of the rotor current. At the core of the system is a power electronics module consisting of the following assemblies: rectifier, IGBT switch (insulated gate bipolar transistor), snubber module, and actuators including some internal control functions. The power electronics module receives the pulse-width modulated switching cycle from the control module. The control module carries out both open and closed loop controls of the start process as well as monitoring and control functions for the blower and short-circuit contactor.

Simple control scenarios such as start-up through constant resistance reduction with adjustable start-up time and adjustable maximum torque are possible. However, constant torque control (stator current) or speed-controlled start-up are also possible. The present state of the art of power semiconductors – especially with regard to high current carrying capacity and pulse frequency – enables the use of this control principle for higher performance applications as well. The ECOSS system is able to handle a rotor starting current of 800 A with a maximum standstill voltage of 1,700 V and is therefore suitable for motors up to a power rating of about 1,500 kW.

Special features:

■ Continuously variable controlled start-up

■ Less wear and tear, reduced mechanical stress

■ Reduced maintenance costs

■ Longer durability of drives and motors

■ No graduation of starting resistor, therefore configuration from identical components

■ Smooth resistance changes even for DC braking possible

■ Integration of the starter in modern control networks via PROFIBUS

■ Integration of the starter into ABB’s diagnostic and parameterisation system Drive Window®.