Electric mobility platforms are proliferating fast. Electric automobiles, Urban Air Mobility (UAM) eVTOL aircraft, high-performance racing platforms, rail traction, and maritime electric propulsion all now demand more power than low-voltage, fuse-protected architectures can deliver. The industry has shifted to high-voltage systems operating in the 400V to 800V range, chosen for high power density and reduced cable mass. At the heart of these architectures sits the High-Voltage Power Distribution Unit, or HVPDU: a safety-critical assembly. It is responsible for reliably switching, protecting, sequencing, and monitoring the flow of electrical energy from traction batteries to propulsion loads.

Industry recalls show what happens when design deficiencies go unnoticed: contactor failures, inadequate pre-charge control, poor fuse ratings, and undetected welded contacts. Each can cause sudden loss of torque, unsafe maintenance conditions, and costly field actions. Designing a High-Voltage Power Distribution Unit (HVPDU) therefore demands far more than electrical interconnections. It requires a disciplined systems engineering approach that brings together electrical, mechanical, software, manufacturing, and verification disciplines into a dependable high-voltage subsystem.

Engineering the HVPDU as a System

Modern electric propulsion systems operate at hundreds of volts while delivering hundreds of amperes under widely varying operating conditions. At these power levels, the HVPDU becomes the critical interface between the battery and the propulsive loads. It is responsible not only for distributing power, but also for enabling safe energization, continuous protection, fault isolation, and controlled shutdown of the motors.

Systems engineering plays an important role in the design of the HVPDU. It starts by translating customer requirements, such as bus voltage, continuous and peak current ratings, fault response times, and HVIL interlock behaviour, into a structured, traceable set of system-level specifications. These specifications govern the detailed hardware and firmware design decisions, so nothing is designed in isolation and every function can be traced back to a verified requirement.

Thus, systems engineering concepts are widely used in the design of the system, the subsystems, and even individual components. High-voltage architecture, embedded software, thermal behaviour, mechanical packaging, diagnostics, continuous insulation monitoring, manufacturing processes, and vehicle integration must be engineered as a single system. Decisions made in one domain directly influence safety, reliability, serviceability, and performance in another.

Our experience in automotive embedded systems is built on disciplined requirements engineering, software architecture, verification, validation, and system integration. Combined with expertise in high-power electronic systems, we approach HVPDU development as a complete engineering program, from concept to verification.

Acsia brings demonstrated expertise in ISO 26262, Automotive SPICE, and MISRA C. Our engineering processes align with AS9100, AIS-004, DO-178C, DO-254, and IEC 60664, positioning us to support high-voltage system development for automotive, industrial, energy storage, defence, and aerospace applications.

Engineering Decisions That Define Reliability

The performance specification of an HVPDU is determined long before the first prototype is assembled. It is shaped by engineering decisions made during system architecture, detailed design, and verification. Every decision involves balancing electrical performance, functional safety, thermal behaviour, manufacturability, and long-term reliability.

Some of the most critical design considerations include:

Controlled System Energization

Traction inverters introduce DC-link capacitance large enough to generate damaging inrush currents if connected directly to the battery. A reliable HVPDU requires carefully engineered pre-charge strategies, controlled contactor sequencing, capacitor voltage verification, and diagnostic supervision to ensure safe and repeatable system energization.

High-Voltage Switching and Protection

Selecting a contactor involves much more than matching voltage and current ratings. Switch-on and switch-off timing and delay, thermal performance, fault-current behaviour, coil-drive strategy, and mechanical endurance all influence long-term reliability. Continuous monitoring of contactor state, weld detection, and controlled shutdown strategies ensure that the system responds predictably during both normal operation and fault conditions.

Continuous Health Monitoring

Reliable operation depends on continuous visibility into the health of the high-voltage system. Monitoring voltage, current, temperature, High-Voltage Interlock Loop (HVIL), Isolation Monitoring Device (IMD), fuse status, and contactor feedback enables early fault detection, effective diagnostics, and timely protective action before abnormal conditions develop into system failures.

Electrical Architecture

Electrical reliability depends on careful engineering of the complete current path. Busbar geometry, arcing, creepage and clearance, insulation coordination, current density, short-circuit withstand capability, and electromagnetic compatibility must be considered together to achieve safe operation throughout the product lifecycle.

Thermal and Mechanical Integrity

Electrical performance can only be sustained through sound thermal and mechanical design. Component placement, heat dissipation, enclosure construction, structural rigidity, vibration resistance, sealing, and manufacturing tolerances all contribute directly to long-term reliability in demanding operating environments.

Each of these engineering decisions influences the others. The result is an HVPDU that performs not as a collection of individual components, but as a fully integrated high-voltage subsystem.

Engineering for Production

Engineering excellence alone does not guarantee a successful product. A production-ready HVPDU depends equally on the strength of the manufacturing ecosystem that supports it.

Qualified component suppliers, busbar fabricators, PCB assembly partners, enclosure manufacturers, cable assembly specialists, environmental testing laboratories, and production test capabilities all contribute to the quality and consistency of the final product. Engineering decisions must therefore account for manufacturability, assembly processes, supply-chain maturity, repeatability, and production verification from the earliest stages of development.

Designing for production is not a final step in the development process. It is an engineering consideration from the outset.

How We Can Support Your Program

Whether you are developing a new high-voltage distribution unit or enhancing an existing platform, Acsia Technologies provides engineering expertise across the full spectrum of high-voltage system design and safety monitoring.

We support applications across electric vehicles (EVs), Battery Energy Storage Systems (BESS), charging infrastructure, marine platforms, rail, transportation, industrial automation, low-voltage/high-voltage test benches, and High-Voltage Power Distribution Units (HVPDUs).

Our services include:

• Concept & System Engineering
• Product Development
• Verification & Validation
• Prototype Development
• Engineering Consulting
• Technology Partner Ecosystem

Our products include:

• Safety monitoring products: HVIL monitoring, contactor health and weld detection solution, and isolation monitoring and fault management system. All are designed to be retrofitted on high-voltage systems for remote monitoring.
• Real-time safety monitoring solution: For use with the safety monitoring products above. Physically taps into the high-voltage equipment to enable monitoring of the HV circuits.

300 kW High-Voltage Power Distribution Unit (HVPDU)

The 300 kW High-Voltage Power Distribution Unit (HVPDU), developed at Acsia, supports reliable battery-to-load power distribution for passenger EVs, commercial vehicles, agricultural and construction equipment, and mining and off-highway platforms. It also serves marine systems, unmanned aerial vehicles, drones, electric and hybrid VTOL air taxis, and other mission-critical electric mobility applications.

SPECIFICATION

• Nominal output voltage: 400V DC, scalable up to 1000V
• Multi-motor connectivity: 2 to 8, with fuses and busbar for efficiency
• HV isolation of Main Positive, Main Negative contactors
• Die-cast Aluminium enclosure
• Operating temperature: -40 to +85°C, 125°C storage
• CAN 2.0 communication at 1 Mbps
• Air-cooled
• IP67 / IP6K9K enclosure
• Industry-standard connectors

SOFTWARE INTELLIGENCE

• Power-on sequence control, fault management, event logging, diagnostics
• Secure boot and hardware root of trust
• CAN FD, 10BASE-T1/1000BASE-T1 based diagnostics

SAFETY & FEATURES

• DC contactors, fuses, circuit breakers, manual service disconnect
• Charging and active discharge control
• Overload and short-circuit protection
• Insulation monitoring devices, current sensors, voltage sensing, temperature sensing
• Fuse monitoring
• DC fast-charge path
• Contactor weld detection
• High-Voltage Interlock Loop (HVIL) monitoring
• Ground fault/isolation monitoring support
• Load distribution control
• Emergency shutdown/crash response

High-Voltage Safety Monitoring Features

These features can be provided as independent products: HVIL, weld detection, IVTS, and IMD.

Figure: Remote multi-node current, voltage, and temperature monitoring solution

Real-Time Safety Monitoring Solution

Provides a real-time view into the state of the safety-monitoring devices and sensors, with alerts on faults.

For HVPDU Development Support

We welcome opportunities to collaborate with OEMs, Tier-1 suppliers, and technology innovators in developing reliable, production-ready HVPDU solutions for the future of electrification.