Electric Motor Repair & Rewinding

1.0 INCOMING INSPECTION

Prior to an incoming run test, we perform the following and record information where appropriate: Motor will be mechanically inspected to determine if shaft turns freely, Verify that bearings are lubricated, Insulation resistance tests are performed. As well as , the continuity of stator windings, condition and installation of brushes, if applicable, Single-phase, low-voltage test (approximately 10-20% of rated voltage) on AC squirrel-cage rotor to find defective rotor bars, Polarization index (where appropriate). Surge test (where appropriate). If conditions permit, the motor will be run at reduced voltage initially (25-50% of rated voltage). If the test is successful, Results are recorded, and then the motor will be run at full rated voltage, if possible. The intent of the “As Received”, no load, run test is to get the motor operating safely up to top speed for electrical characteristics, bearing temperature, and vibration checks prior to dissassembly. If the “As Received” motor conditions permit, the motor shall be run to 100% speed for these tests.

A thorough appraisal of the motor’s condition, as received, is to be performed, to determine what specific repairs are needed as well as to find unsuspected trouble, perhaps unrelated to the obvious defect. Our technicians diagnose cause and effect to help prevent a recurrence. The motor may have been sent to our Repair Facility with limited external evidence as to the nature and location of trouble. What seems wrong may be correctable in several ways. Our appraisal will include a complete review of the following conditions of each part of the motor: General cleanliness, Cracked or broken welds or castings, Missing hardware, Wear or rub marks, including fretting, discoloration, charring, or other evidence of overheating, Looseness at mating fits, Corrosion, moisture, or oil inside the machine. 

All mechanical parts are to be thoroughly cleaned and inspected for defects, cracks or damage at 44 points. Visually check for evidence of rubbing at outside diameters (fan, shrouds, end rings, armature laminations, etc.). If possible, a check is made for tightness of the core on its shaft. Visual inspection for signs of axial and radial movement are made. Visually check rotating components for excessive heating and other abnormalities, as well as an Inspection of condition of bar joints, end rings, windings, slip rings, key ways, threaded fits, synchronous pole pieces, etc. Furthermore, measure and record dimensions of the following: Shaft extension, Journal and bearing fits, Shaft extension runout, Shaft seal fits, Collector ring diameter, Brush size and type of quantity, as well as visually inspect the condition of non-rotating components (brackets, baffles, shrouds, brush holders, brushes, gasket, spacers, shims, threaded fits, machine fits, feet, etc.). and measure and record bracket fits for housings, cartridges, and bearings, the condition of ball or roller bearing housing or cartridges (wear, grooving, seal fits, fretting, grease fitting, insulation, oil gages, etc.),the condition of sleeve bearings while still in brackets (wear, oil grooves, oil rings, seals, insulation, seal fit, bracket ware, dowels, parts, etc.),stator laminations, mounting blocks, welds, machined fits, brush rigging, space heaters, etc., inspect rotor pole pieces, mounting blocks, amortisseur windings, leads, etc. Terminal boxes should accommodate the connections without crowding. Missing terminal boxes should be replaced, and damaged terminal boxes should be repaired or replaced. Gaskets and seals should be replaced where necessary. The fans and cooling ducts should be clean and operational. Cover plates and air baffles should be in place. Damaged or missing parts of the cooling system should be repaired or replaced. Any Damage appraisal of motor components is divided into two categories, electrical and mechanical. 

After the insulation tests, the motor shall be run at no load at full terminal voltage, with either a half key or a half coupling, on the shaft. If the motor uses an external oil supply and removal system in normal use, a similar system shall be arranged for the test. The motor is to be run at nameplate voltage, frequency and speed. Record the no-load current drawn on all phases and document. Run test shall be a minimum of 45 minutes duration at the rated voltage and until the temperature of the bearings have stabilized (+/- 1°C over 15 minutes). On squirrel-cage motors, check the current on all connections and check speed of the motor. The current on each phase should be within 10% deviation between any two other phases. On wound rotor motors, apply full primary voltage to stator and with rotor circuit open for a non-rotational test. Rotor open circuit voltage and stator current is measured. A non-load test run will be made on all motors to ensure that all electrical readings do not exceed the Name Plate Data ratings. A written record of all tests and inspection results will be furnished to the user upon completion of repairs. 

At Electromechanex, LLC we take pride in reliability engineering, isolating the root cause of the failure and repairing your motor to the highest possible standards and workmanship with the highest standard of reporting in the industry, as our intent is to let you know how to prevent the failure from happening again. As an EASA member, we serve as a total solutions provider for electrical and mechanical equipment and systems.

Mechanical

Electrical