A New Foundation for Critical Power Conversion

Building the Cornerstone of Tomorrow’s Grid

If “AI” continues to be the buzzword capturing today’s news headlines, then Solid State Transformers (SSTs) might be up next in the limelight – and for good reason. As AI scales, a greater lens is on the upstream power sources that are expected to keep up with rapidly expanding data center deployments. One could argue that the race to commercialization for medium voltage-capable, multi-megawatt solid-state transformers (SST) to solve this power problem is an achievement in and of itself. But given the relative reliability of traditional transformers and electrical equipment for AI loads, SSTs will need to demonstrate a high bar of reliability to achieve commercial success.

Enter Amperesand

Amperesand has been developing medium voltage (MV) to direct current (DC) SST technology for a decade in Singapore. In the past two years the company has dramatically accelerated development, bringing to market their 3^rd generation SST purpose built for AI factories, building across their rapidly growing design and manufacturing sites in Reno, NV, San Francisco, and Singapore. Amperesand’s deep SST development foundation has been strengthened by a diverse team with demonstrated experience developing and scaling energy products to mass deployment across Tesla, Google, Amazon, Microsoft, Eaton, ABB and others.

Amperesand is focused on critical power for AI factory loads, commercializing the first medium voltage SST-to-rack power solution capable of providing 5-10MW of modular power conversion for the emerging 800 VDC AI compute ecosystem. Their newest product is setting multiple industry benchmarks in reliability, power capacity, power density, efficiency, cost, and safety. Reliability is the fundamental requirement of critical power systems, and Amperesand is designing and testing to demonstrate 15+ year lifetime for the SST with components that enable this demanding reliability need.

Amperesand’s New Approach to An Age-Old Infrastructure Challenge

The Amperesand SST is a perfect fit for converged infrastructure powering AI Factories. Amperesand’s design provides best in class MV and DC power quality by eliminating bulky, long lead-time line frequency transformers and large, electrically noisy rectifiers otherwise required for a DC-native compute ecosystem. This approach simultaneously enables Amperesand’s customers to replace uninterruptible power supply (UPS) systems with lower cost, multi-sourced battery energy storage that smooths AI power fluctuations and provides rack power backup matched to site-level power architectures. The SST is much more intelligent than prior UPS systems, enabling grid ride through, ramp rate control, and demand response to ensure AI factories achieve excellent grid inter-operability performance, required for interconnect in today’s grids. The Amperesand SST is future proofed via hardware and software to efficiently support increased AI compute power, cybersecurity and emerging grid interconnect standards.

Amperesand’s ambition for uptime is to decisively compete with traditional AI power infrastructure technology. The company’s obsession with design and validation to achieve best-in class reliability was exactly the design philosophy that cemented a two-way engineering partnership with Wolfspeed.

This case study will examine three foundational performance promises of Amperesand’s silicon carbide (SiC) based medium voltage SST:

Two Companies. One Reliability Mission.

SiC is a key enabling technology for the modern SST. By leveraging 3.3 kV full-bridge Wolfspeed WolfPACK modules in the MV front-end, Amperesand was able to optimize power density, efficiency, and cost by dramatically reducing the number of power stages while still maintaining redundancy, serviceability, and margin to support medium voltage stresses. Wolfspeed’s modules provide additional voltage margin over typical medium-voltage SST operating voltages, which enables additional redundancy in voltage overshoot scenarios. Additionally, the modules include an ultra-durable die – integrated Wolfspeed Gen 4 MOSFET technology enables excellent cosmic ray performance, exceeding the expected FIT rates across the installation mission profile.

The early partnership began crystallizing when Amperesand approached the Wolfspeed reliability and applications team to understand the SiC lifetime against emerging AI power cycling profiles. Amperesand provided a variety of critical power mission profile scenarios, including AI training workload conditions as jointly released by NVIDIA, Open AI and Microsoft¹, and Wolfspeed got to work developing extensive mission profile lifetime analysis.

Wolfspeed’s new 3.3 kV module includes epoxy encapsulation for added mechanical stability. Based on the failure criteria Amperesand provided to Wolfspeed and as shown in the chart above, the SiC in the Amperesand SST achieves a near infinite lifetime due to low ΔT (<30°C), enabled by a highly innovative liquid-based cooling system that unlocks 50º C+ ambient operation to support AI factory critical power in any environment. Wolfspeed’s epoxy-filled package achieves a 5X improvement in power cycling performance over standard silicone gel encapsulated modules.

Early lifetime predictions based on the modeling work then pivoted to hands-on work in Wolfspeed’s Fayetteville, AR facility as thermal characterization began to more accurately predict the performance of Amperesand’s advanced cooling system. Wolfspeed leaned into a challenging test schedule by taking on the full design and fabrication of thermal characterization PCBs and hosting characterization in-house for maximum acceleration.

Simpler Serviceability

Wolfspeed’s 3.3 kV WolfPACK module enables reliability far beyond the substrate. Amperesand leverages the WolfPACK’s higher voltage performance to right-size the power stages in its modular architecture for serviceability – without sacrificing cost, connection count, or power density. Service and maintenance will inevitably be part of the story of long-term reliability for SSTs, as is the case for any power infrastructure equipment. The key is to keep maintenance predictable, seamless, and easy to schedule.

The use of Gen 4 SiC keeps Amperesand’s power stages small and light enough for simple two-person replacement in minutes, using readily available lifts, all while meeting the rigors of medium voltage operation during runtime. A simple, user-friendly power stage replacement process ensures customer downtime is kept to a minimum as SSTs strive to support “five nines” availability.

Through the partnership with Wolfspeed, Amperesand is also able to leverage the wide operating range of Gen 4 SiC in combination with advanced in-house medium voltage thermal systems design to support proprietary redundancy and failover architectures within the SST. This redundancy and failover architecture also gives customers room to support increasing AI compute power demands in future generations. This way, customer AI workloads experience rock-solid nonstop power delivery with predictable windows for scheduling coordinated SST maintenance. A complete software suite – from predictive maintenance to site-level asset visibility – rounds out Amperesand’s offering of a new standard for digitally native datacenter power infrastructure serviceability.

Designing for Worst-Case Scenarios

In many ways, it’s not just hardware design that differentiates the SST. The safety of 800 VDC AI factory operators and service technicians is a key focus of technology development in the Amperesand SST. The company’s advanced power electronics controls, firmware, and software are designed to provide optimized load fault coordination and settable ultra-fast shutdown of energy delivery to reduce arc flash incident energy compared to traditional approaches. This multi-layered safety feature set is enabled by SiC thanks to the high thermal overload capability and high switching rate supported in new module generations.

From lifetime, to serviceability, to safety, Wolfspeed and Amperesand are working together to position medium voltage SST products as the reliable, safe, and cost-effective cornerstone of tomorrow’s power infrastructure.

Amperesand is now accepting orders with industry-best lead times. Learn more about the product and how to get started.

For more information on the 3.3 kV WolfPACK modules powering Amperesand, view the datasheet here.

About Amperesand 

Since launching in 2023, Amperesand has translated a decade of proven R&D into commercial medium voltage SST critical power systems developed for customers with gigawatt-scale energy demands. They bring together a team of over 130 world class leaders and engineers united by a singular passion to revolutionize critical power conversion for AI factories and the grid at scale.

Sources:

1. Power Stabilization for AI Training Datacenters