Background

Electric motors may become damaged if they are subjected to fuel or lubrication oil, contaminated water, salt water, etc., even though the motor is not energized. Technicians must recognize the need for reconditioning a damaged stator and be able to determine which method should be used to clean the motor. Using the correct cleaning method may permit a damaged stator to be successfully reconditioned. More information on reconditioning stators can be found in Chapter 8 of NAVSEA 0900-LP-060-2010 Series.

Testing and inspecting a disassembled stator

Conduct an insulation resistance to ground test and record results on the motor data sheet (electrical).

Do NOT conduct a dc high-potential test if the motor is grounded.

Conduct a dc high-potential test and record results on the motor data sheet (electrical).

Determine the type of contamination present (i.e., fuel and lube oil, salt water). Refer to NAVSEA 0900-LP-060-2010 Series to determine the appropriate method to use to clean the windings based on the type of contamination and the size of the motor.

Approved cleaning methods are: suction, wiping, air pressure, water washing with compounds, and steam spray with compounds.

Cleaning by use of suction

Vacuum suction is the preferred method to remove dry materials like dust, chips, and dirt (also grit, iron, and copper particles). Vacuum suction is preferred over compressed air because suction is safer and there is less chance of damaging windings. You should also use this cleaning method during and after stoning of commutators or slip rings and when seating brushes.

Be certain that the tube or nozzle on the end of the vacuum hose has no sharp projections which might scrape the insulation. Do NOT allow loosened debris to be pushed or pressed into inaccessible openings. This will cause more serious problems.

A flexible hose connected to the suction side of a portable vacuum cleaner may be used. Use a soft brush to remove any foreign matter sticking to the winding, then pick up the debris with the vacuum.

Cleaning by wiping

Take care when removing material using this method. Chips or other rough matter adhering to the cloth may scratch or remove insulation. Do NOT allow loosened debris to be pushed or pressed into inaccessible openings. This will cause more serious problems.

This method uses a dry lint-free cloth or a clean sash brush to wipe loose dust and foreign particles from exposed stator surfaces.

Click on image to enlarge.

Typical Motor Data Sheet (Electrical)