# 48V DC and OCP Bus Bar Traditional servers each have their own power supply unit (PSU) that converts AC to 12V DC internally. The OCP (Open Compute Project) bus bar architecture eliminates individual PSUs by converting power at the rack level. **How it works:** 1. AC power enters the rack 2. A rack-level [[rectifier]] converts AC → 48V DC 3. The 48V DC bus bar distributes power down the rack 4. Each server has a simple 48V → 12V converter (much cheaper and more efficient than a full PSU) **What gets eliminated:** - Individual server power supplies (CRPs — Common Redundant Power supplies) - Per-server AC-DC conversion losses - Dozens of failure points per rack **Why this matters:** Fewer components means fewer things that break. A traditional 42U rack might have 20+ individual PSUs, each one a potential failure point. The bus bar architecture replaces all of them with one or two rack-level converters plus simple step-down boards per server. Efficiency improves because you're doing one high-quality AC-DC conversion instead of twenty mediocre ones. The 48V distribution also means lower current (and thinner cables) for the same power delivery compared to 12V distribution. **Where Delta applies this:** Their MDC product line uses 48V DC distribution with OCP bus bars as the standard power architecture. This is not experimental — it's the production design. --- See also: [[Power Usage Effectiveness - PUE]] | [[Modular Data Centers MoC]]