Grounding of AC row cabinet

AC row cabinets must be grounded to a main earth system using low-resistance connections to ensure safety, EMC compliance, and protection against electrical faults.

Purpose of Grounding

Grounding an AC cabinet serves multiple purposes: it protects personnel from electric shock, prevents damage to equipment, and reduces electromagnetic interference (EMI). Any stray voltage or fault current is safely conducted to the earth through the cabinet's metal frame, avoiding the risk of current passing through a human body, which has much higher resistance than copper conductors ( ).

Grounding Methods

Protective Earth (PE) Connection The cabinet frame should be connected to the main ground bar or earth reference plane using a dedicated grounding conductor. This ensures that all metal parts of the cabinet are at the same potential and integrated into the facility's higher-level earthing system ( ). Earth Reference Plane or Rail Install an unpainted copper plane or rail on the cabinet floor.

All metal components, including mounting rails, backplanes, and filters, should be bolted directly to this plane to maintain a low-resistance path for fault currents ( ). Cable Shield Grounding Control and power cables with shields should be grounded at the cabinet entry point. The shield should have 360° contact with the cabinet frame to minimize high-frequency EMI and maintain EMC compliance.

The grounding distance and impedance should be as short and low as possible ( ).

Inter-

Cabinet Bonding In multi-row installations, adjacent cabinets should be bonded together to maintain a common reference potential. This can be achieved using copper busbars or braided grounding straps connecting the frames of each cabinet ( ).

Installation Considerations

Direct Bolting: Use locknuts or bolts to ensure all connections are mechanically secure and electrically continuous. Plastic Cable Ducts: Allowed if mounted systematically on DIN rails or cage structures that are themselves grounded.

EM

C Compliance: Follow standards such as EN 61800-3 for industrial environments and ensure grounding reduces reactance for high-frequency currents ( ). Safety Codes: Installations must comply with NEC (NFPA 70) or local electrical codes to ensure personnel safety and equipment reliability ( ).

Summary

Proper grounding of an AC row cabinet involves connecting the cabinet frame and all internal metal components to a main earth system using low-resistance conductors, grounding cable shields at entry points, and bonding multiple cabinets together. This ensures personnel safety, equipment protection, and EMC compliance, while providing a reliable path for fault currents and high-frequency disturbances ( ).