Vehicle HV network overview
A modern EV high-voltage network connects the traction battery to propulsion and auxiliary loads through controlled, protected distribution. Typical nodes include the battery pack, main HV distribution (PDU or integrated module), traction inverter, onboard charger path, DC/DC converter, and thermal or cabin HV loads.
Architecture choices affect harness complexity, packaging volume, fault isolation, and service strategy across passenger EV, commercial EV, bus, and specialty platforms.
Where the PDU sits in the architecture
In a discrete-PDU architecture, the EV PDU is the central HV distribution and protection node between the battery connectors and the load branches. It implements contactor sequencing, pre-charge, fusing, and status feedback so the VCU/BMS can energize and isolate the bus safely.
Cable length, voltage drop, connector count, and underbody versus pack-adjacent packaging all influence where the PDU is physically placed.
PDU role vs CDU / integrated power modules
A discrete EV PDU focuses on distribution and protection. An integrated CDU (combined power distribution unit) may package OBC, DC/DC, and PDU functions into one mechanical assembly to reduce harness joints and packaging volume.
Neither approach is universally better. Discrete PDUs offer clearer module boundaries and easier swap for some platforms; integrated CDUs can simplify vehicle packaging when OBC and DC/DC share cooling and connectors. Choose based on platform roadmap, supplier strategy, and service model.
- Discrete PDU: clear HV distribution ownership, flexible branch changes
- Integrated CDU: fewer harness interfaces, shared thermal/packaging envelope
- Hybrid: discrete PDU plus separate OBC/DC/DC when supplier or timing differs
Branch loads and distribution strategy
Map every HV branch early: traction inverter, fast-charge or OBC path, DC/DC, heaters, compressors, and any specialty loads. Current class, fuse strategy, and connector selection follow from that map.
- Main propulsion path continuous and peak current
- Charge path isolation and mutual exclusion with drive enable where required
- Auxiliary HV branches and their protection hierarchy
- Sense and control lines for each contactor or protection device
Control, HVIL, and safety interfaces
Architecture is incomplete without control ownership. Define how HVIL, crash signals, BMS enable, and contactor feedback interact with PDU logic — hardwired, CAN-based, or mixed.
Incorrect sequencing between pre-charge, main contactor, and vehicle interlocks is a frequent prototype failure mode. Freeze interface timing before locking the mechanical design.
Passenger vs commercial and specialty platforms
Passenger EV programs often prioritize packaging density and NVH. Commercial EV and bus platforms typically demand higher continuous current, tougher vibration profiles, and service-friendly access. Specialty vehicles may add unique HV loads that force branch customization.
TRHT supports both discrete EV PDU and integrated CDU program paths so OEMs can align architecture choice with volume plan and supplier strategy.
Frequently asked questions
When should an OEM choose a CDU instead of a discrete PDU?+
Consider an integrated CDU when OBC, DC/DC, and distribution share packaging and cooling goals, and when reducing harness joints outweighs the flexibility of separate modules. If charge and conversion suppliers differ or timelines diverge, a discrete PDU is often simpler.
Does architecture change the PDU electrical ratings?+
Yes. Branch count, charge topology, and voltage class (for example 400V vs 800V) change continuous/peak current, protection devices, and connector sets. Architecture drawings should accompany the RFQ electrical map.