SiC modules for UPS can lower conversion losses in continuously operating power stages. The resulting savings include both electricity that the UPS no longer wastes and cooling energy that the facility no longer needs. In high-power online UPS systems, these recurring savings can offset the higher acquisition cost of SiC modules and reduce total cost of ownership.

As UPS systems continue to operate around the clock, improving power conversion efficiency is an effective way to reduce operating costs and enhance overall system performance.

What is an online double-conversion UPS, and where is SiC used?

An online double-conversion UPS continuously processes power through an AC-DC rectifier and a DC-AC inverter, delivering a stable and clean AC output to critical loads regardless of input power disturbances. Many systems also include a bidirectional DC-DC converter that manages energy flow between the battery storage system and the DC link.

SiC power modules can be implemented in all major power-conversion stages, including the active front end (AFE), inverter, and bidirectional battery converter. By enabling higher efficiency and power density, SiC helps optimize UPS performance while reducing energy losses and thermal management requirements.

Block diagram of a power conversion system showing AC input, rectifier, inverter, static bypass, DC-DC converter, and battery storage connected to supply a load

Block diagram of online double-conversion UPS

Why are power losses a key consideration in UPS systems?

Power losses in a UPS are converted into heat instead of useful output power. As a result, operators pay not only for the electricity lost during power conversion but also for the additional energy required to remove that heat through cooling systems. For continuously operating online UPS systems, efficiency directly affects both energy consumption and cooling requirements, making it a key contributor to total cost of ownership.

The financial impact increases with power level, operating hours, utilization, and electricity costs. In online double-conversion UPS systems, where power is processed continuously, even small efficiency improvements can generate significant savings over the system lifetime. Reducing semiconductor losses can also lower thermal stress on cooling and power system components. For this reason, UPS efficiency is an important factor when evaluating total cost of ownership.

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How do SiC modules help optimize UPS systems?

Optimization level 1: Reduce conversion losses

SiC power modules help improve UPS efficiency by reducing switching and conduction losses in the active power-conversion stages. In an online double-conversion UPS, these stages typically include:

  • AC-DC rectifier or active front end (AFE): Converts incoming AC into a controlled DC-link voltage and provides power-factor correction
  • DC-AC inverter: Produces stable AC for the protected load
  • Bidirectional DC-DC converter connected to the energy storage system: Controls charging and discharging between the energy-storage system and the DC link

Optimization level 2: Reduce cooling energy and thermal stress

Because less power is dissipated as heat, SiC-based UPS designs can reduce cooling requirements and thermal stress on system components. Lower operating temperatures can help simplify thermal management, improve reliability, and contribute to lower operating costs over the system lifetime.

Optimization level 3: Improve power density

The higher switching capability of SiC modules enables the use of smaller passive components and more compact converter designs. This can increase UPS power density, helping designers reduce system size and better utilize installation space without compromising performance.

Optimization level 4: Simplify topology where feasible

Beyond efficiency improvements, SiC can change the economic balance between topology complexity and performance.

Based on Infineon's UPS topology and loss analysis, a two-level CoolSiC™ solution can achieve lower losses than comparable two-level and three-level silicon implementations.

As a result, engineers can evaluate whether a simpler two-level power stage can meet efficiency targets without the additional switches, gate drivers, and control complexity associated with multilevel silicon designs for a given load.

How to calculate operating-cost savings?

SiC modules reduce operating costs by lowering converter losses, which in turn decreases both electricity consumption and cooling demand.

A practical way to compare UPS designs is to evaluate the cost of energy losses over the system lifetime rather than considering efficiency figures or module prices in isolation.

Use the following relationship for each candidate design:

Annual loss cost = UPS output power × operating load factor × loss percentage × annual operating hours × electricity price × cooling factor

In Infineon's 1 MW UPS analysis, a system operating at 50% load over five years processes approximately 22 million kWh of energy. It then applies a cooling factor of 1.2 and an electricity price of €0.10 per kWh. The resulting comparison is shown below.

Under these stated assumptions, the SiC case reduces the calculated five-year loss-related cost by €39,000 compared with two-level silicon and by €31,000 compared with three-level silicon. These are differences within Infineon’s example, not universal savings values. Changes in load, tariff, cooling performance, topology, and operating profile will change the result.

The three-level silicon implementation also demonstrates that topology optimization alone can reduce losses and operating costs compared with a conventional two-level silicon design.

When SiC pays back?

The higher upfront cost of SiC modules should be evaluated against the operating savings they can enable throughout the UPS lifetime.

In conventional silicon IGBT-based designs, switching losses increase significantly as switching frequency rises. Designers often face a trade-off between improving efficiency, increasing power density, and managing thermal performance.

SiC power modules help overcome this limitation by significantly reducing switching losses while maintaining low conduction losses. This allows UPS designers to operate at higher switching frequencies, improve efficiency, reduce heat generation, and potentially decrease cooling requirements. As a result, the total cost of ownership may be lower despite the higher initial investment.

The potential savings can include:

  • Reduced converter energy losses
  • Lower cooling energy consumption
  • Smaller or simplified cooling systems
  • Improved power density and optimized system design
  • Reduced operating costs over the system lifetime

A practical payback calculation is:

Payback period = additional SiC system investment ÷ annual energy and cooling savings

The exact payback depends on factors such as UPS load profile, electricity costs, operating hours, cooling requirements, and the selected power-conversion topology.

Design checks before moving to SiC

The primary system-level benefit is lower recurring energy cost. Lower heat generation can then create additional design options like reduced cooling demand, fewer or smaller heatsinks, more compact filters, increased output from an existing enclosure, or greater thermal margin. Infineon’s CoolSiC™ can cut energy losses by half in 24/7 online UPS operation and can reduce the number of heatsinks and filters required.

The designer should not count all these benefits simultaneously without verifying the final architecture. Thermal headroom may be used to raise output power rather than reduce cooling, for example. Likewise, higher switching frequency may reduce filter size but introduce additional EMI and layout work.

To achieve the full benefits of SiC technology, the power stage, gate drive, layout, thermal design, and EMI strategy should be optimized as a complete system rather than treating SiC as a direct replacement for a silicon-based solution.

Why Infineon’s CoolSiC™ modules for UPS optimization?

Infineon’s CoolSiC™ modules combine SiC MOSFET technology with established module platforms and complementary gate-driver and control solutions.

For a UPS designer, the relevant value is the ability to evaluate modules together with topology, gate drive, protection, sensing, control, and thermal requirements rather than treating the power switch as an isolated component.

CoolSiC™ modules are most compelling where the UPS operates continuously and the financial value of lower loss is measurable. Selection should begin with DC-link voltage, power rating, current, switching frequency, topology, load profile, cooling method, and target loss. The designer can then compare the SiC investment against modeled lifetime energy and cooling costs.

CoolSiC™ modules can provide the greatest value in UPS systems where higher efficiency, lower cooling requirements, increased power density, or reduced system complexity contribute to lower total cost of ownership. Designers should evaluate these benefits against the specific performance, cost, and operating requirements of their application.

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CoolSiC™ MOSFET power module in Easy 2B package for UPS

CoolSiC™ MOSFET power module in Easy 2B package

FAQs

1. Do SiC modules improve efficiency at partial UPS load?

Yes. SiC modules can reduce switching and conduction losses at partial load, helping improve UPS efficiency across a wide operating range. Actual gains depend on the system topology, switching frequency, and operating conditions.

SiC modules can be used in the rectifier (AFE), inverter, and bidirectional DC-DC battery converter stages. They deliver the greatest benefit in continuously operating power stages, where lower losses can reduce both energy consumption and cooling requirements.

Yes. In continuously operating UPS systems, lower energy and cooling losses can offset the higher upfront cost of SiC modules. The actual payback depends on the application's load profile, operating hours, electricity costs, and system efficiency improvements.

No. IGBT modules can remain a cost-effective choice for lower-frequency and cost-sensitive UPS designs. Full SiC is most beneficial in continuously operating systems that require higher efficiency, higher switching frequencies, reduced cooling effort, and lower total cost of ownership.

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