35 kV ARC FURNACE VOLTAGE CONTROL UPGRADE
THE MANUFACTURER’S CHALLENGE
This arc furnace project was initiated by ongoing maintenance demands and reliability limitations associated with circuit breaker-based switching in a critical arc furnace voltage control system. Frequent servicing requirements, limited equipment lifespan, and the potential for unplanned downtime contributed to increased operational costs and reduced system availability. In addition, inconsistent switching performance impacted process stability, while maintaining aging equipment in an outdoor high-voltage environment added further complexity. A more durable, low-maintenance solution was required to enhance reliability, extend service life, and ensure consistent performance in a demanding steel production setting.
COALMONT’S TURN-KEY SOLUTION
Coalmont designed and built a complete replacement of high-maintenance circuit breakers in SSAB's 35 kV inductor voltage control system with advanced Siemens vacuum contactor technology for their arc furnace operations. The comprehensive design-build project included twelve Siemens 24 kV vacuum contactors rated 800A (36 total vacuum bottles) configured to switch two three-phase inductors, two custom NEMA 3R outdoor enclosures powder-coated ANSI grey with reinforced forklift slides and crane lifting eyes, nine outdoor Hubbell power bushings rated 3000A and 34.5 kV with 200 kV BIL, internal surge arrestors for both input and output protection, shielded 38 kV cables with 3M stress cone kits, Allen-Bradley ControlLogix PLC interface for contactor pilot relays, integral air conditioning and lighting systems powered by 480 VAC, comprehensive factory acceptance testing including full voltage HiPot tests and high current tests at low voltage, complete engineering drawings and documentation in three sets with USB drives, and onsite commissioning with first-day operational standby support.
This reliability upgrade project reflects a custom-engineered medium voltage switching solution designed to dramatically reduce maintenance requirements while improving overall performance. SSAB gained vacuum contactors rated for 1,000,000 operations (5-10 times longer life than circuit breakers), dual outdoor enclosures designed for both forklift and crane installation matching existing concrete pad locations, same bushing configuration as existing system enabling straightforward retrofit, comprehensive shop testing validating performance before shipment to minimize installation risk, complete system designed for serviceability with options for spare components and modular replacement, reduced maintenance costs through elimination of high-maintenance circuit breakers, and improved reliability for critical arc furnace voltage control. This project demonstrates specialized experience in medium voltage system design, vacuum switching technology, outdoor industrial enclosure fabrication, factory acceptance testing protocols, and arc furnace electrical systems within the steel industry.
CAPABILITIES: Medium Voltage Design | Vacuum Contactor Systems | Shop FAT | Custom Enclosure Fabrication