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In the meantime, heat dissipation is only generated during the short period of starting and stopping phases. This is how the soft starter altogether reduces mechanical stress. In comparison to the frequency converter, the soft starter is not only of a much smaller build, but also can boast efficiency above 99 percent. The settings of starting and stopping parameters are easy to handle. By this feature, voltage control and voltage ramp can be individually defined. Due to these characteristics, soft starters nowadays are used in almost all industrial applications, especially for drives that require a soft torque process or reduction of starting currents as well as weak networks. In comparison to the frequency converter, the soft starter can claim a much lower failure rate, so that its failure rates are considerably below those of the converter. The reason behind this is the built-in Thyristors, which are more reliable and soft starters are not equipped with IGBTs.
Typical starting procedure of a motor with a soft starter
The ISA-SL Appliance Range represented a product highlight for the Company in 2014 and impressively emphasises market leadership in softstarters
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Analogue and digital
For simple applications with small to medium power below 250 kW, the manufacturer offers analogue soft starter units with two-phase control, which are generally without integrated bypass-contactor. Those units are easier to handle and are promoted as an alternative to the star-delta starter. An added advantage is that only in-line connection is required, eliminating the need for six-wire connection dictated by star-delta configuration. In low voltage and medium voltage installations, digital soft starter units with three-phase control, are used for demanding industrial applications. The units offer adjustable current-limits and complete motor protection, such as