Drives & MCC Control Systems. A motor controller is a device that controls the performance of an electric motor. It might include a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and faults. A motor control center (MCC) groups these motor controllers and related devices in one compact structure. A motor control center consists of one or more enclosed vertical sections mounted on the floor. It contains incoming line facilities, a common horizontal bus, wireway trough, and conduit facilities for incoming and outgoing wires. Each vertical section typically contains a vertical bus connected to the power bus, a vertical wireway, one or more combination motor control units, and various related devices, including push buttons, selector switches, etc.
Things to Consider: Ampacity (horizontal bus), Vertical bus ampacity, Fault current rating, Current interrupting device rating, Short-circuit rating, Meets section 110.10 of the 2005 NEC, Bussing material (copper preferred in general but aluminum is best in corrosive atmospheres), Feeder cable entry method (overhead or underground), Control wiring type for automatic controls, Enclosure type: indoor (NEMA 1) or outdoor (NEMA 3R), Ground-fault detection, Metering, Wire-marking, Indication lights, Hands-off auto switches, Voltage rating.
Electrical Controller. A device that governs in some predetermined manner the electric power delivered to an apparatus or system.
Things to Consider: Operating voltage, Power rating, Current draw, Operating temperature range, Relative humidity range, Mounting dimensions, Minimum mounting clearances, Duty cycle, Use and User of system, Warranty.
MMI & OIT Control Systems. Man Machine Interface (MMI) and Operator Interface Terminals (OIT) are operator interfaces with which users interact in order to control other devices. Some include knobs, levers, and controls. Others provide programmable function keys or a full key pad. Devices that include a processor or interface to personal computers are also available. Many include alphanumeric or graphic displays. Some are web-enabled. Others include software drivers, a stylus, and support for a keyboard, mouse, and printer. Devices that are designed for harsh environments include enclosures that meet standards from the National Electronics Manufacturers’ Association (NEMA).
Things to Consider: Adequate lighting, Wheelchair accessible, Ease of use for normal ranges of manual dexterity, Legible labels, Numbered instructions, Controls reachable from wheelchair, Display screen, keypad, and/or controls shielded from sunlight, Parallax minimized or eliminated, Multi-lingual or Bilingual capabilities, Simple vocabulary, Inductive loop facility, Audio jack socket, Audible feedback of keyboard input, Speech output, Video link, Telephone layout for numeric keys, Raised dot on number 5, Clear visual markings on keys, Raised or recessed keys, Well spaced keys, Internally illuminated keys, Tactile feedback on keys, Generous time allowed for key input, Option to increase character size on display screens, Large key fields on touchscreens, Text accompanying graphical symbols, Speech output option, Security provisions, Instructions at least 16 point type size, Good contrast text, No background patterns, Easy to read typefaces, Short line lengths, Instruction manual, Instructions on audio tape or by video, Training provisions.
Purge Panel. Purge panels are designed to automatically flush explosive gases out of the control enclosure by sending a protective gas such as instrument air or an inert gas through the system until enclosure volumes have been exchanged. After the purging cycle is completed, power can be applied to protective enclosure. These panels usually contain controls similar to the following: shatter-proof windows, pressurization valves, regulated and differential pressure gauges, low-pressure alarms, and purge valves.
Things to Consider: National Fire Protection Association (NFPA) 496 standard, UL/CSA certification, Flameproof, Automatic and manual purge, Panel fabrication to be cold rolled – close annealed (CRCA) pressure tight construction, Dimensions, Weight, Shape, Volume available for electrical equipment, Two compartments (purged electrical and non-purged non-electrical) Cable entry point, Accessories such as illumination and service plug sockets, Paint type and color, Control wiring type, Power wiring, Electrical input, Control supply (VAC), UPS power supply availability, Front controls, Control circuit, Front instruments, Inside instruments, PLC, Main logic, Warranty.
