Conventional (monolithic) vs Modular UPS System

Modularity refers to

  • An engineering technique that builds large systems by combining smaller systems
  • A systems components maybe separated and recombined
  • Use of exchangeable parts or options in the fabrication of an equipment

Conventional UPS system is built mostly based on monolithic concept i.e. a UPS system will have a rectifier and inverter bridge of its rated capacity to support the loads.

The conventional UPS can also be based on modular construction concept i.e. a UPS system will have 2 or 3 subassemblies of rectifier and inverter bridge which works together to form the full capacity of the UPS

  • MTBF – Mean Time between Failures
  • MTTR – Mean Time to Repair

Monolithic vs Modular UPS

The conventional UPS systems can work in standalone configuration or can be paralleled to improve the capacity or to improve the redundancy levels.

The Monolithic UPS will have

  • Low Component Count  High MTBF*
  • Fixed Components High MTTR*

Modular construction concept will have the same characteristic like monolithic UPS but will have higher availability.

  • Low Component Count High MTBF
  • Serviceable Components Medium MTTR

The key advantages of Modular construction when compared with monolithic construction are

  • Power Modules
    • Based on standard pre-engineered modules
    • Inter – operatability of modules
  • Internal Redundancy
    • N+1 Redundant Fans
    • Failure of modules will lead only to reduced UPS capacity
  • MTTR
    • Shorter mean time to repair
  • Accessibility
    • Front Access Design with slide out Modules for easy serviceability

Modular UPS System

The Modular UPS will be built up with multiple smaller UPS modules and number of UPS modules is paralleled to achieve the desired level of redundancy

The Modular UPS will exhibit a

  • High Component CountLow MTBF
  • Hot swappable UPS module Low MTTR

Why modular UPS

  • Flexibility
  • Right Size of Infrastructure
  • Scale up or Scale down based on the load agility
  • Quick to deploy
  • Availability Use of exchangeable parts or option in the fabrication of an equipment
  • Reduced MTTR
  • Total Cost of Ownership
  • Optimized Capex & Opex
  • Improved RO


Figure 1 Fixed vs adapted infrastructure

Availability Comparison of Monolithic vs Modular UPS



Comparison Of Foot Print Monolithic vs Modular UPS


Comparison Of Conventional UPS Vs Modular UPS



In conclusion, Modular UPS approach isn’t always the best solution to all scalable UPS needs, but it should be thought over as a part of a general UPS strategy. In addition, in order to see the entire picture, selection of a modular approach requires thorough knowledge of the particular UPS design including detailed information about common items like controller and battery.