Electrical hazards¶
The wind tunnel draws three-phase mains power to a VFD which drives a three-phase induction motor. Treat the VFD enclosure as a high-voltage cabinet at all times.
What is energized when¶
| Component | Energized when | Notes |
|---|---|---|
| Main switch upstream of the VFD | Always, until physically opened | The mains feed is live at the switch terminals even when the switch is open. Treat as live. |
| VFD enclosure busbars | Main switch closed | Three-phase 480 V to the input rectifier. |
| VFD DC link | Main switch closed; remains charged briefly after opening | Bus capacitors retain charge. Vendor minimum wait is 5 minutes after de-energizing before opening the cabinet. |
| Motor terminals | Main switch closed; only spinning when drive is commanded | The motor terminals can carry voltage while the drive is enabled even if the rotor is not turning. |
| RETA-01 fieldbus adapter, Ethernet 4 adapter | Lab PC powered (low voltage) | Communication-side only; safe to handle. |
Rules¶
- Never open the VFD enclosure with the main switch closed. No exceptions.
- After opening the main switch, wait at least 5 minutes before opening the VFD cabinet, to allow the DC-link capacitors to discharge.
- Lockout/tagout the main switch any time the cabinet must be opened: a physical lock through the switch handle plus a tag identifying who placed it. UCI EH&S policy reference: Hazardous Energies / LOTO program.
- Do not touch motor terminals while the drive is enabled, even at zero commanded speed. The motor sees PWM voltage whenever the drive is enabled.
- Inspect cabling before each run. Visible damage to any power cable means: stop, isolate, repair, then resume — never tape over and continue.
- No liquids near the VFD or the main switch. Smoke-generator fluid spills are an electrical hazard; clean immediately with the run paused.
Arc-flash and high-voltage references¶
- UCI EH&S Electrical Safety Program (PDF): https://ehs.uci.edu/programs/_pdf/safety/electrical-safety-program.pdf
- UCI EH&S High-Voltage Electrical Safety Program (PDF): https://www.ehs.uci.edu/programs/_pdf/safety/high-voltage.pdf
- UCI EH&S Energized Electrical Work Reference Guide (PDF): https://www.ehs.uci.edu/safety/_pdf/Energized-Electrical-Work-Guidance.pdf
What's inside the VFD¶
The drive is an ABB ACH550 configured for fieldbus control via a RETA-01 module in option slot 1. Critical parameter values that must be present for remote operation are documented in Reference → Parameter index. If any of them drift, Maintenance → Parameter recovery is the recovery path.
The drive is configured, not programmed, through its front keypad. Never modify parameters from the keypad without recording the change in a milestone log — the parameter map is the difference between "the tunnel works" and "the tunnel does not work" and there is no automated backup.