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PLC-free system is an alternative to replacing MCCs

27 February, 2015

US-headquartered Schweitzer Engineering Laboratories (SEL) has announced a centralised control system that monitors, controls and protects low-voltage motor installations. The motorMax system offers a low-cost alternative to replacing existing motor control centres (MCCs), while allowing users to keep up with modern safety requirements. It also eliminates the need for PLCs, thus simplifying motor management.

The system provides motor protection functions based on voltage, current and power. It includes a patented thermal model that allows simultaneous tracking of the effects of positive, negative and zero-sequence currents in both the stator and rotor of a motor.

“We have leveraged SEL’s time-proven power system protection technology to bring smart motor controls to a whole new level,” explains Scott Manson, SEL’s engineering services technology director.

The system includes a high-speed arc-flash detection technology that reacts in as little as 16ms to spot arc-flash events and trip upstream breakers to protect personnel. “Arc-flash detection and mitigation are effective methods for reducing incident energies in old MCC gear,” says Manson.

A remote HMI allows operators to control motors from a safe distance. The HMI displays warnings, alarms and status signals. To help troubleshoot and diagnose faults, the system records time-synchronised sequences of events automatically.

A typical installation using SEL's motorMax motor management system

Time synchronisation between the system’s relays is accomplished using the Simple Network Time Protocol (SNTP). A standard Modbus interface allows control systems to monitor and control MCCs remotely. A typical round-trip time for controlling a motor contactor is 100ms or less.

The turnkey system can be scaled to any size of MCC, and ships configured, tested and ready for assembly into MCCs. It includes feeder protection relays, managed Ethernet switches, real-time automation controllers, precision time sources, and interfaces for local or remote visualisation and control.

Users “don’t need to enter any relay or controller settings because all devices come pre-configured and tested,” Manson explains, adding that this can save hundreds of hours of engineering work for a typical MCC.

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