What are Motor Control Centers and How Do They Work?
Motor Control Centers (MCCs) are specialized electrical assemblies designed to centralize the control, protection, and distribution of power to multiple electric motors within industrial facilities. These integrated, modular units organize motor starters, variable frequency drives (VFDs), programmable controllers, and associated components into efficiently packaged structures that provide significant space savings and operational benefits.
MCCs work by housing multiple motor control units within a common structure, typically featuring a main power bus that distributes electrical power to individual motor control units. Each unit, often called a "bucket" or "cell," contains all the necessary components to control and protect a specific motor. The modular design allows for standardization, easy maintenance, and future expansion while providing a systematic approach to motor management across a facility.
Key components of a Motor Control Center include:
- Vertical Sections: Free-standing metal enclosures containing multiple motor control units
- Horizontal and Vertical Bus Bars: Conduct electricity from the main power source to individual units
- Motor Control Units: Removable modules containing starters, protection devices, and control components
- Motor Starters: Contactors and overload relays that control motor operation and provide protection
- Circuit Breakers or Fuses: Provide short-circuit protection for each motor circuit
- Control Devices: Pushbuttons, selector switches, pilot lights, and other operator interface components
- Variable Frequency Drives: In modern MCCs, for speed control and energy efficiency
- Power Monitoring Equipment: Meters and instruments to monitor electrical parameters
- Communication Systems: Network interfaces for integration with facility automation systems
Uses and Applications
Motor Control Centers serve crucial functions across various industries:
Manufacturing Facilities
- Production line motor control
- Conveyor systems
- Material handling equipment
- Machine tools and processing equipment
- Packaging machinery
Process Industries
- Pump stations for water, chemicals, and petroleum products
- Mixers and agitators
- Fans and blowers for ventilation and process air
- Compressors for air and refrigeration systems
- Refineries and chemical processing equipment
Infrastructure Applications
- Water and wastewater treatment plants
- HVAC systems for large commercial buildings
- Data center cooling and air handling systems
- Mining operations
- Power generation facilities
- Oil and gas installations
Important Considerations Before Buying Used Motor Control Centers
Usage and Maintenance History
Understanding the operational history helps evaluate condition and reliability:
- Verify age and service environment (clean/dirty, wet/dry, temperature extremes)
- Request maintenance records and history of preventive maintenance
- Check for evidence of overheating, arcing, or damage to bus bars
- Confirm contactor and breaker operation count if available
- Inspect for signs of water damage or excessive dust/dirt accumulation
- Verify condition of stab connections between units and main bus
- Check for modifications, retrofits, or replaced components
- Confirm that all original units are present and operational
Specifications and Compatibility
Ensure the MCC meets your system requirements:
- Voltage rating must match your power system (typically 208V, 240V, 480V, 600V)
- Current rating of main bus adequate for all connected loads
- Short-circuit current rating (SCCR) appropriate for your facility
- Starter sizes appropriate for your motor horsepower ratings
- Controller types suitable for applications (FVNR, FVR, VFDs, soft starters)
- Enclosure type suitable for environment (NEMA/IP rating)
- Physical dimensions compatible with installation space
- Cable entry locations (top/bottom) compatible with your conduit layout
- Type of bus bar material (tin-plated copper, aluminum) and condition
Purpose and Application
Select MCCs appropriate for your specific needs:
- Environmental conditions at installation location
- Required level of motor control and protection
- Need for advanced features (VFDs, soft starters, PLCs)
- Communication and automation integration requirements
- Accessibility for maintenance (front-only or front/rear access)
- Future expansion needs and availability of matching sections
- Serviceability and spare parts availability for older equipment
- Energy efficiency considerations
- Arc flash safety features for personnel protection
How Much Should I Budget for Motor Control Centers?
Pricing varies based on size, features, and condition:
New Motor Control Centers
- Basic MCC sections: $8,000-$15,000 per vertical section
- Standard NEMA starters: $1,500-$5,000 per unit depending on size
- VFD units: $3,000-$10,000+ depending on horsepower rating
- Smart MCCs with networking: 30-50% premium over standard versions
- Arc-resistant designs: 40-70% premium over standard designs
- Complete MCC lineup (5-8 sections): $50,000-$150,000+
Used/Reconditioned Motor Control Centers
- Typically 30-60% of new pricing depending on age and condition
- Refurbished with warranty: 50-70% of new pricing
- As-is condition: 25-45% of new pricing
- Testing and certification costs: $2,000-$8,000 depending on size
- Transportation and rigging: $2,000-$10,000 depending on size and distance
- Installation costs: $5,000-$20,000 depending on complexity
- Retrofitting costs for obsolete starters: $1,000-$3,000 per unit
Cost Factors to Consider
- Age: MCCs under 15 years generally command higher prices
- Technology: Newer control technologies add value
- Manufacturer: Premium brands maintain higher resale value
- Condition: Evidence of good maintenance increases value
- Documentation: Complete schematics and manuals add value
- Modernization costs: Updating to current standards
- Spare parts availability: Critical for older equipment
- Energy efficiency: Older equipment may have higher operating costs
- Compliance: Updating to meet current electrical codes
When purchasing used MCCs, thorough inspection by qualified electrical professionals is essential. The complex nature of these assemblies means that internal components may have varying degrees of wear. Particular attention should be paid to the main bus condition, insulation integrity, and operation of critical components like contactors and circuit breakers. While used MCCs can offer substantial savings, the critical role they play in facility operations makes proper evaluation and testing particularly important. Factor in potential refurbishment costs, code compliance updates, and long-term serviceability when assessing the total cost of ownership.