Softstart UK launches new 6.6kV digital softstarter
04 September 2009
Responding to rising demand from the market, Softstart UK has designed a completely new, digitally controlled medium voltage soft-starter, the first of its kind to be designed and built in the UK. An initial unit, rated at 3.3kV and 110A has been delivered to site and will shortly be commissioned.
The currents drawn by high power motors usually demand they are installed on a medium voltage supply, usually 3.3 or 6.6kV. However, the starting surges of these motors can cause a great deal of damage and only one method of starting control offers well considered programming and sensitive protection along with smooth current and torque control. Soft-stopping can be as vital as soft-starting and the MV DS soft-starter provides soft stopping as a standard feature.
In soft-stopping mode, the output voltage is gradually reduced over time until the motor stops. This avoids abrupt and potentially damaging stops, an advantage in many pumping and conveyor applications. Although full VSD control offers excellent starting and stopping control, where speed control is unnecessary, a 3.3kV soft-starter is one fifth of the cost of a full variable speed drive.
The new medium voltage range of soft-starters is currently available for supplies up to 6.6kV and 720 Amps, with a 400% overload for 30 seconds, satisfying the starting needs of motors up to 6.7MW and the designs to extend the range to 11kV and 700A well underway. The design features full user-friendly digital control and monitoring via an 8.1ins front-mounted industrial PC with Ethernet and Modbus control capabilities and the touch screen offers multi-lingual programming as standard. Bi-directional motor control is optional, as is power factor correction and slip-ring motor control with rotor resistance shorting. The design also accommodates generator set operation with wide 45-65Hz auto frequency tracking.
Important optional features such as withdrawable line and bypass contactors, switch fuse disconnects and grounding switches have all been catered for, full motor protection is incorporated and IP54 protection is a standard feature, with top, bottom and rear cable entry and side entry can be specified as an option. Despite the comprehensive design, lead time has been cut to a mere 6 weeks as opposed to the several months experienced for such high power drives in the past.
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