Electricity and Control July 2021

DRIVES, MOTORS + SWITCHGEAR : PRODUCTS + SERVICES

Soft starter upgrades mill operation

between the control section and the high voltage operational side. In particular, the functionality test in the soft starter’s software is able to test each individual fibre optic cable using a control voltage of 230 V, before the system is opened to the full 6 600 V used for operations.

Providing an improved starting method for the rod mill of a process plant in Mpumalanga, Zest WEG has supplied a WEG SSW7000 medium voltage soft starter. This installation formed part of an upgrade which also saw a 450 kW, 8 pole, 6 600 V WEG W50 motor with a direct online starter. Fritz Hoogenboezem, Branch Manager at Zest WEG Middelburg, says the new soft starter was imported into South Africa from WEG’s Brazil factory in time for the plant’s scheduled shutdown, and was installed by local systems integrator Umagezana Engineering. “By avoiding the sudden in-rush of current when the motor is switched on, the soft starter reduces the mechanical stress on equipment and the peak load drawn from the national power grid,” says Hoogenboezem. Reducing peak consumption to a lower peak demand delivers a direct financial benefit to the customer. This is because exceeding the maximum demand – as can occur when a large motor starts up – leads to costly penalties being applied by the power utility. The in-rush current to start a heavy-duty load can, in those first few milliseconds, be seven to ten times higher than the level at which the motor is specified. “By exceeding the maximum demand, the plant could pay much more than necessary for its power consumption, not just for that month but on an ongoing basis,” he says. Umagezana Engineering Director Ernest Bean, says the installation of the soft starter was a complex task. Once the direct online starter had been removed, it was clear that the cable lengths would not fit directly onto the new soft starter. “This required changes to be made in the motor control centre (MCC) on the high voltage side,” says Bean. “The different cable lengths meant that cables had to be re-terminated to ensure safe and compliant operation; nine cores or phases were terminated.” Another challenge was that the door to move the equipment in and out was not wide enough. This required specialised rigging to be carefully planned and set up, as the WEG SSW7000 soft starter weighs almost a tonne. Once the new equipment was installed and connected, Zest WEG’s qualified drives and automation technician Reiner Gundlach assistedwith the cold and hot commissioning. Extensive tests were run in accordance with WEG’s detailed OEM specifications, laying the technical foundation for the optimal performance and lifespan of the equipment. “With a sophisticated medium voltage item, there are numerous aspects that need checking and testing,” says Hoogenboezem. “The results are then communicated with WEG as part of our rigorous quality management procedures.” Bean highlights that, as a technician in the field, he was impressed by the smart use of fibre optics

“Another benefit of the soft starter is its monitoring functionality, which allows the plant management to track the interaction between the motor, the soft starter and the plant PLC, closely,” he says. “Management can at any time log into the PLC and use that interface – together with the soft starter – to view important information such as tonnages processed and the number and duration of stoppages.” Umagezana Engineering was appointed by Zest WEG as a distributor for the WEG low voltage switchgear range in January 2021. Its whole team has also recently completed the required MV training for high voltage terminations and cable joints, which was done through a specialist firm accredited by the Energy and Water Sector Education and Training Authority (EWSETA).

Inner body of the MV soft starter with the fibre optic cables.

For more information contact Zest WEG. Visit: www.zestweg.com

An Umagezana Engineering technician terminating a 6.6 kV cable.

Electricity + Control JULY 2021

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