Case: From Pre-Compliance to First-Time Pass — Industrial PSU in a US Control Panel
Customer: Automation OEM integrating a 24 V rail with I/O, sensors, and drives inside a compact cabinet.
Goal: Select a compliant PSU, avoid first-time-fail, and release to production before a fixed installation window.
0
Lab re-runs
Lab re-runs
2×
Faster selection
Faster selection
>6 dB
Conducted margin (worst channel)
Conducted margin (worst channel)
Challenge
Early bench tests looked fine, but the cabinet with long cable bundles and mixed loads triggered conducted peaks and cold-start trips at low line. The schedule allowed only one formal test slot.
Approach
- Model pick & headroom — Sized continuous ×1.4 with motor/valve peaks; selected alarm/relay and redundancy options.
- LISN sweep (cabinet-level) — Representative loads and full wiring; logged worst channel and margin.
- ICL + EMI filter — Coordinated ICL with breaker curves; added CM choke + X/Y + damping. Verified start-up at low temp/low line.
- Cable & shield policy — Separated noisy vs. sensitive runs; consistent shield termination at entry panel.
- Thermal check — Validated temps with stacking and enclosure airflow; derated per ambient.
- Docs pack — One-pager (levels, pass/fail, photos), label snapshot, and wiring diagram for buyer/inspector.
Results
- First-time pass for conducted emission & immunity; no re-spins.
- Predictable start-up across cold/low-line; ICL & breaker coordination documented.
- Buyer-ready docs (one-pager + label + wiring) cut PO approval time.
What We Used
- UL-listed DIN-rail PSU for cabinet integration.
- Programmable supply for bench validation & profiling.
- Bidirectional module for source/sink and regen scenarios.