By Dovydas Kersys · Chapter 23 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.
Motor direction must be proven in a controlled way before full-speed or mechanically loaded operation. With line-start motors, phase sequence determines direction; with VFDs, phase sequence at the drive input usually does not determine motor direction, but motor output wiring and drive direction logic do.
A short controlled jog is safer than discovering direction during the first automatic cycle.
Why this matters during commissioning
Wrong direction can damage pumps, conveyors, fans and process equipment before a technician has time to react.
Commissioning procedure
- Identify the required direction at the machine, not only on the motor shaft.
- Use a short low-speed jog with the load in a safe condition.
- Observe direction and stop immediately if incorrect.
- Correct using the approved method: phase swap, output lead swap or drive direction setting as appropriate.
- Retest limit switches, feedback and process flow after correction.
Common failure patterns
- Arrow on motor fan mistaken for machine direction.
- Pump briefly operated dry or backwards.
- Encoder feedback direction not corrected after motor direction change.
- HMI forward/reverse labels opposite to actual motion.
Evidence to record
- Measured value and test point
- Expected value / expected state
- Observed value / observed state
- Pass/fail result and any deviation
- Name/date or responsible person where required
FIELD RULE: Verify the direction of the machine function, not merely the direction of the motor.
Continue the series
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Adapted from Machine Commissioning for Maintenance and Automation Technicians, by Dovydas Kersys. © 2026 Dovydas Kersys. Featured cover image is an AI-generated editorial illustration.