Power Supply and Phase Checks: Commissioning Guide

By Dovydas Kersys · Chapter 10 of 58 in Machine Commissioning.

Before you begin: Follow the machine documentation, risk assessment, site procedures and lockout/tagout requirements. Commissioning can expose personnel to electrical energy, stored pressure and unexpected motion. Never defeat a safety function merely to make a test easier. Examples and diagrams are generic and must be checked against the actual machine.

Incoming power should be verified before sensitive loads are connected or enabled. Check voltage magnitude, phase-to-phase balance, phase sequence, neutral where used, and expected grounding arrangement.

Simplified commissioning training diagram for Power Supply and Phase Checks

Verify phase sequence before running mechanically coupled three-phase loads.

Why this matters during commissioning

Wrong supply voltage, lost phase or incorrect phase sequence can immediately damage equipment or make pumps and fans run backwards.

Commissioning procedure

Verify supply matches design nameplate values.
Measure phase-to-phase and phase-to-neutral voltages where applicable.
Check phase rotation using an appropriate tester.
Confirm control transformers and power supplies are connected to the intended taps.
Energize distribution progressively, watching for abnormal current, noise, odor, heat or trips.

Common failure patterns

Incorrect transformer tap.
Phase loss due to fuse or terminal problem.
Neutral missing on a circuit that requires it.
Unexpected backfeed from another panel.

Evidence to record

Measured voltages
Phase rotation
Transformer tap / supply configuration
Breaker/fuse state
Abnormal observations

FIELD RULE: When possible, energize from upstream to downstream instead of bringing the whole machine live at once.

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