Synchronous Motor Reliability Check: Offline PDMA Testing + Dry Ice Cleaning
Continental technicians completed offline PDMA testing and dry ice cleaning on a hydrogen compressor motor, capturing before-and-after test data and documenting key condition indicators across the main motor and excitation system. The work produced trendable results, verified auxiliary protection components, and improved external contamination while noting access limitations for deep internal winding cleaning with the rotor installed.
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Overview
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Western Canadian Plant in the Energy Sector
Western Canadian Plant in the Energy Sector
Work Required:
offline testing + CO₂ cleaning with documented results for trending on a Hydrogen compressor motor
The Challenge:
This was a preventive reliability scope: confirm electrical condition, reduce contamination, and create traceable baseline data for trending.
Testing identified signs of contamination in PDMA results, plus limitations on cleaning access to internal winding areas due to rotor position.
Our Work On Site:
Testing + Cleaning Scope
- Offline PDMA testing conducted before and after Dry Ice cleaning
- Cleaning scope included: Main Stator, Main Rotor, Exciter Stator, Exciter Rotor, and filters
- Additional testing included: winding/bearing RTDs, CTs on motor leads, space heaters, diode assembly, field monitoring, and surge protectors
Findings and Observations
- PDMA results showed some improvement from before to after cleaning, indicating benefits from contamination removal on accessible surfaces.
- The PI graph indicated contamination within the PDMA results; however, insulation resistance remained well above acceptable operating limits after cleaning.
- The main stator IR was lower than previous historical data, which is an important trending flag. One key limitation noted during the work: deep access to clean the inside of the windings is restricted while the main rotor remains installed, which can limit how much internal contamination can be removed during an on-site cleaning scope.
- The main rotor low-voltage drop readings varied across poles, reinforcing the value of recorded baseline data and ongoing monitoring.
To ensure the motor was returned to service-ready condition with documented workmanship:
- RTDs were verified to be functional, and other thermal protection devices tested well
- Diode gating, surge protectors, and field monitoring were tested and confirmed to be operating correctly
- Air gaps were measured for both the exciter and the main stator/rotor
- Diode plates were reinstalled; bolts were torqued, secured, and lock seals applied where required
- Main stator leads and exciter leads were torqued/tightened, and filters were reinstalled with the hood and cover bolts secured
The customer received:
- A cleaned motor (as accessible on-site) with strong before/after visual documentation
- Before-and-after offline test results are suitable for trending and maintenance planning
- Confirmed operation of critical monitoring/protection components (RTDs, heaters, CTs, diode/field monitoring, surge protection)
- A documented set of observations that clearly explains what improved, what remained unchanged, and what limitations exist when cleaning internal winding areas with the rotor installed
Outcome
Before
Aux Box Before Dry Ice
Motor Before Dry Ice
Filter Before Dry Ice
After
Aux Box After Dry Ice
Motor After Dry Ice
Filter Before Dry Ice