Soft starts go underground in Russia

Lonodn - A Russian coal mine is set to become one of the most technologically advanced in the world, as it prepares to install a UK-built explosion-proof soft start, for its massive conveyor system, which carries coal from the working face to the mine shaft. The unit rated at 6000V, 800kW makes the conveyor fully automatic and is designed to simultaneously start three separate 400kW motors that run the mine’s main gate conveyor.

The kit was designed and built by Sheffield-based Baldwin & Francis (B&F), from an OEM kit of parts supplied by Soft Start UK of Great Yarmouth. It comprises thyristor power modules, a fibre optic EPT for firing the thyristors and an electronic control module and user interface. The  custom-designed system had to be compact as space was limited; requiring that the thyristors be supplied with specially-made right angled couplings rather than conventional in-line ones. Use of fibre optics electrically isolates the high- and low-voltage parts of the soft start and removes the possibility of flashovers.

Cooling of the soft start was a major design consideration so that the electronic components could be used with confidence in such an aggressive environment. Several options were considered, with forced draught be chosen because it would be the most reliable over the expected long working life of the equipment.

"The worldwide mining industry is still fairly new to electronic solutions to do with starting motors underground and we are doing a lot of pioneering work in this respect." said Mark Ramsden of B&F. "Electronics tend not to like the heat and gases typically found underground, and the thought that they may cause a spark is an anathema to mining engineers the world over. It is our job to show that electriocs is robust enough and staht sparking isn’t a problem.”

Until four or five years ago all mine-based conveyor starting would have been via a fluid coupling, but the there is now a definite trend to more modern ideas, according to B&F. Likewise, Soft Start UK claims growing interest in its medium-voltage soft starts, particularly from the heavy and harsh environment industries such as quarrying, groundwater pumping, offshore, waste management and recycling.