Prefabricated power modules have become a de facto standard in modern data center construction. Factory integration. Rapid deployment. Reduced land utilization. These attributes make modular power systems especially attractive in an era defined by speed-to-market and capacity elasticity.
Yet behind this apparent uniformity lies a striking divergence in design philosophy, particularly between domestic configurations and those commonly adopted in North America. The reasons are not aesthetic. They are structural, thermal, and regulatory.
Integrated Power Modules: Compact by Design
In many domestic projects, the power module is conceived as a highly compact, linear assembly. Dual utility incomers. SVG or reactive power compensation. Bypass switches. UPS outputs and UPS units. All arranged in a single lineup.
Outgoing feeders from the switchgear connect directly to the UPS through rigid copper busbars. The layout is dense. Spatial efficiency is maximized. Installation is fast. The entire system is typically housed inside a standard shipping container, forming a complete, transportable power block.
From a construction standpoint, this approach is elegant. From a system-integration standpoint, it is aggressive.
Why the Same Structure Fails in the U.S. Market
In the United States, such an all-in-one lineup is generally unacceptable. The reason lies in the fragmentation of standards.
Low-voltage switchboards must comply with UL 891.
UPS systems are subject to UL 9540A, UL 1973, and related safety certifications.
Each standard imposes its own structural, thermal, and spacing requirements. Combining these devices into a single lineup violates certification boundaries and complicates compliance.
Heat is another decisive factor. UPS systems dissipate substantial thermal energy. Placing them adjacent to low-voltage switchgear increases ambient temperature around breakers and busbars, directly affecting current-carrying capacity and long-term reliability.
As a result, U.S. data centers typically adopt a split architecture:
One lineup dedicated to power distribution panels
A separate lineup dedicated to UPS systems
Interconnection achieved via power cables rather than rigid busbars
Segregation is deliberate. And it is non-negotiable.
High-Density Switchboards Under UL 891
UL 891 switchboards are inherently compact. For data center applications, this compactness is pushed to the limit.
Common configurations include:
Two 3000–4000 A frame circuit breakers housed within a single 1 m-wide switchboard
Or four 2000 A frame breakers integrated into a cabinet only 550 mm wide
Front-access maintenance alone is often insufficient. Side cabinets are added to accommodate incoming and outgoing copper busbars, as well as high-capacity cable terminations. Space efficiency is achieved, but only through meticulous mechanical design.
Medium-Voltage Integration: Compact by Necessity
Where medium-voltage utility supply is introduced, compactness becomes even more critical.
Two solutions dominate:
IEEE C37.20.9 compliant gas-insulated switchgear (GIS)
IEEE C37.20.3 metal-enclosed air-insulated switchgear
Both are designed to minimize footprint while maintaining arc containment, insulation integrity, and serviceability. In modular data centers, medium-voltage equipment is rarely oversized. Every millimeter matters.
Container Constraints: Geometry Dictates Design
For prefabricated containerized power modules, physical dimensions impose absolute limits.
A standard container offers:
Internal width: approximately 2.35 m
Internal height: approximately 2.39 m
Operational requirements quickly consume this space. A maintenance aisle alone typically demands at least 1 m. Switchgear rear clearance adds another 0.2 m. That leaves a maximum allowable equipment depth of roughly 1.15 m.
This constraint drives aggressive miniaturization, especially for large-current switchgear. Designs that work comfortably in substations often become infeasible inside containers.
Thermal Reality Inside Containers
Thermal behavior inside a container bears little resemblance to that of a conventional indoor substation.
In substations:
Large room volumes dilute heat
Natural convection is effective
External ventilation often suffices
Air conditioning may be unnecessary
Inside a container:
Air volume is minimal
Heat accumulation is rapid
External heat dissipation through container walls is limited
Temperature differentials between cabinet interior and ambient air shrink
As temperature differentials collapse, so does cooling efficiency. Switchgear temperature rise increases. Ratings erode. Reliability suffers.
In practice, containerized power modules almost always require active cooling systems. Air conditioning is no longer optional. It is structural.
North American Alternative: Purpose-Built Outdoor Enclosures
In North America, prefabricated data center power systems frequently abandon the standard container altogether.
Instead, they employ custom outdoor enclosures, drawing on decades of experience with outdoor switchgear. Two dominant forms exist:
Outdoor Switchgear Without Maintenance Corridors
These cabinets are serviced directly from the exterior. Doors open outward. The enclosure itself provides protection against rain, snow, solar radiation, and UV exposure.
Thermally, this approach excels. Heat dissipates directly into the outdoor environment. Current-carrying capacity improves. Temperature rise becomes far less restrictive.
Outdoor Switchgear With Integrated Corridors
When internal access is required, enclosures incorporate maintenance corridors. Dimensions are defined by equipment, safety clearances, and transport constraints. Structures may be shipped as complete units or assembled on-site.
These enclosures integrate:
Ventilation and cooling systems
Fire detection and suppression
Internal arc pressure relief
Environmental sealing
Form follows function. Transport convenience never overrides system integrity.
System Integration as a Design Philosophy
A power module is not a packing exercise. It is a systems-engineering problem.
Effective integration considers:
Functional coordination
Thermal independence
Certification boundaries
Maintainability
Fault containment
Long-term reliability
Custom outdoor enclosures allow switchgear, UPS systems, and auxiliary equipment to be arranged rationally, not forcibly. Standard containers, while convenient for logistics, often impose compromises that surface later as operational risks.
Closing Perspective
Modularity should never mean rigidity. The objective of a data center power module is not merely to fit equipment into a box, but to ensure safe, stable, and predictable operation under real-world conditions.
Transport efficiency matters.
But reliability matters more.
True system optimization begins not with container dimensions, but with electrical behavior, thermal physics, and standards compliance.