AC & DC  Generator Repair, Inspection, and Maintenance services

When it comes to long-term reliable service, industrial generators have no rival. The near constant ability to stay active despite power failures and major systematic errors is impressive. Manufacturing plants inherently rely on the wide functionality of these generators to keep their business lively and productive. We not only repair and refurbish your Generator but to provide root cause failure analysis on why it has failed, and provide ongoing maintenance services.

  Our comprehensive Generator Service, makes repairs, when you need them, performed to state-of-the art standards. Shop and Field Service support capabilities include 24 hour service, 7 days a week.

Our Generator Repair services include:

  • Reconditioning – Repair, reconditioning, and adjustment of the Generator• Stator components’ parts are thoroughly cleaned and baked dry. Replacement of Bearings, Seals and any auxillary componants, as required.
  • Rewinding – Complete refurbishing of the Generator• Stator componants are rewound with inverter rated magnet wire using NEMA Class “H” insulation system.Replacement of Bearings, Seals and any auxillary componants, as required.
  • Modifications – We offer application design and assistance, plus the capabilities of modification of New Generators to meet your specific requirements.
  • Testing – Generators are tested using non-destructive winding analysis and testing and test run for proper electrical and mechanical operation. Output Voltage, Speed, Bearing temperature, and Vibration are closely monitored and documented.
We know Generators! Contact us for a Generator Repair Quote, a Replacement Generator, or Predictive Maintenance Plans.

Repair Service for all types of Generators in the following categories:


  • (AC) Alternating Current
  • (DC) Direct Current
  • Deisel
  • Natural Gas
  • Liquid Propane
  • (MG) Motor-Generator Sets
  • Portable

An electric generator is a machine that uses mechanical energy to produce electrical charges and move them through an electric current. Its engine creates mechanical energy which is pushed through an electrical conductor in a magnetic field, creating electric charges and generating electric current. A generator has various components, including an engine, an alternator, a fuel system, a voltage regulator, cooling and exhaust systems, a lubrication system, a battery charger, a control panel, and a frame or main structure.

Incoming Inspection

EMX Motor Repair Shop performs a thorough appraisal of the Generator’s condition, as received, to determine what specific repairs are needed as well as to find unsuspected trouble, perhaps unrelated to the obvious defect. Our Mechanic’s diagnose cause and effect to help prevent a recurrence. The generator 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 Generator: 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. Digital Photographs of any abnormal conditions found are part of the appraisal process and inspection report. Our Generator Repair includes dissassembly, detailed inspections, and measurements to identify electrical and mechanical damage.

Incoming Tests

Prior to an incoming run test, we perform the following and record information where 2016-08-12 08.07.53appropriate: Generator 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, Polarization index (where appropriate). Surge test (where appropriate). If conditions permit, the generator will be run at reduced speed initially (25-50% of rated voltage). If the test is successful, Results are recorded, and then the generator will be run at full rated speed, if possible. The intent of the “As Received”, no load, run test is to get the generator operating safely up to top speed for electrical characteristics, bearing temperature, and vibration checks prior to dissassembly. If the “As Received” generator conditions permit, the generator shall be run to 100% speed for these tests.

Disassembly & Inspection

Before any disassembly is begun, parts will be marked (i.e., brackets, frame, covers, and brush holders). Brackets and bearings will be identified as pairs. Check and record rotor air gap.  Frame-mounted devices will be identified and recorded. Electrical wiring is recorded, sketched, and marked before disconnecting (for external connection).

The condition of the Field & Armature windings and the extent of repairs are determined by inspection and, as necessary, by testing. Coil windings are observed for the following: Slot Wedges (“top sticks”) that are loose, damaged, or have shifted in position. Ties, lashings, or blocking that are loose or broken. Dirt, oil, or moisture deposited on coil surfaces. Coil damage – Besides obvious burning, tracking, or charring, look for loose or cracked tape, coils that have moved within the slot, deposits of dirt or chemicals, and insulation pitted or worn away by airborne abrasive particles. Winding integrity is determined using non-destructive winding analysis and testing. In a DC Machine, the Commutator is machined and undercut and Armature windings are examined for evidence of defects. Additional Testing may be required.

Generator components & parts are thoroughly cleaned. Steam cleaning is the preferred method. Shafts will be checked for wear, cracks, scoring and straightness. (NEMA MG 1-2003 Rev.1-2004, Section 1, Part 4 Par. 4.11); cracks, corrosion; scoring or galling. Shaft extensions should be smooth, polished and concentric with the shaft center. Shaft extension dimensions and permissible runout will be checked and Diameter Tolerances for NEMA/IEC frame size machines compared. Keyseat/ Keyway Width Tolerances checked against NEMA/IEC Frame Size machines Tables. Keyseats will be true TM-5-3810-232-340057imand accommodate keys to tap fit. If the shaft requires repair, worn surfaces can be restored within our Machine Shop to factory specification. Ball or Roller Bearings (Antifriction bearings) are comprehensively inspected for condition of lubricant; dirt, rust, or moisture; fretting corrosion; thermal discoloration; pitting or spalling of balls, rollers, or races; broken or missing retainers. Sleeve Bearings are checked to be uniform in diameter, of proper fit in the housing, smooth internally and suitably grooved for adequate distribution of lubricant.  Bearing Housings and Shaft bearing fits are measured and compared to manufacturer’s specifications. Any fits that are not within tolerance are restored to original factory specification. Seals & Seal clearance are set to original equipment manufacturer’s specifications if available. Oils used will be compatible with the customer’s lubricant Frame and Bearing Housings will be examined for defects; Corrosion; structural weld integrity; blocked drains, breathers, or ventilating air passages; paralleling of feet. Cracks and breaks are repaired and fits restored to manufacturer’s specifications.

Additional Generator components, such as the alternator, fuel system, voltage regulator, cooling and exhaust systems, the lubrication system, and battery charger are inspected and tested. Space heaters are tested for rated current or power and subjected to a high-potential test. They will be replaced if damaged. Bearing temperature sensors or protectors will be identical with or equivalent to the original devices in electrical and thermal characteristics.

Balancing Armature

EMX Shop Balancing Systems are designed to perform measurements of vibrations and stacks_image_1428calculations in horizontal shop balancing machines and in the field. The application measures the running speed (1X) filtered vibration amplitude and relative phase with a reference mark in the rotor to allow full balancing correction. Dynamic Balancing results are to be performed to the level specified by the customer.  In the absence of a requested level, dynamic balancing to balance quality grade G2.5 (ISO 1940/1) should enable the machine to meet final vibration limits. Note: Balance Weights are to be located so that they do not interfere with other machine components.

Recondition of Field Coils & Armature

Electrical components’ parts are thoroughly cleaned. Steam cleaning is the preferred method. Cleaning will continue until all vent slots are free of any obstruction which may interfere with proper cooling of the motor. Insertion of any metal object into ventilation passages of a Fields or Armature is unacceptable under any circumstances. Prior to an re-insulating application, the windings will be preheated to 110°F to 130°F to remove air and moisture. Oven temperature will not exceed 290°F during the drying cycle for Class “F” or “H” insulation. Oven temperature will not exceed 250°F for Class “A” or “B” insulation. A Final megger reading must exceed 1 megohms at room temperature., at which time either the spray or flow method or the “Dip and Bake” method can be used.  A reading below 10 megohms requires communications with the User and determination will be made as to rewind the Fields or Armature verses the cost of motor replacement.

In the event that Rewinding of Field Coils or Armature is the better choice in the repair of the Generator, the winding will be re-manufactured using an inverter rated magnet wire and the insulation exclusively classified as follows: NEMA Class “H” An insulation system (180°C temperature limit including a 40°C ambient or 140°C rise) that by experience or 2-0-and-5-0kw-Type-Aluminium-winding-Generator-Parts-Stator-Rotor-armature-accepted test can be shown to have suitable thermal endurance when operating at the limiting Class H temperature specified in the temperature rise standard for the machine under consideration. The entire Insulation System, materials, and methods of application should be equal to or better than that used by the original machine manufacturer. All components of the insulation system will be compatible with each other with respect to electrical, mechanical, and thermal characteristics. RTDs or thermocouples are placed within the windings if they were part of the original design or requested to be added by the User. Generators are rebuilt using the highest-quality wire, insulation, and varnish materials for long-lasting repairs in the most severe industrial environments.


All mechanical repairs on shafts, bearing journals, end bells, and other equipment are handled in-house by experienced machinists. All Generator assemblies are made in accordance with good machine shop practices. If the shaft requires replacement, a new shaft will be made of A.I.S.I. 4140 Steel HRHT (Hot Rolled Heat Treated). Under special cases, shaft material will be replaced with 316 stainless or User approved material. Generator will be assembled in a manner that will ensure proper fit and alignment. Ball and Roller Bearings are fitted to shafts by heat-expanding the inner bearing race in accordance with the bearing manufacturer’s recommendations, however, not to exceed 250°F, using an oil-bath heater or an induction heater. Check and record air gap. All bolts, nuts, etc., will be replaced as required with SAE grade 5 or better and torqued to Industry standards. On metric fasteners we will use a grade 8.8 or better. All assembled components will be checked to ensure secure fits. All covers on openings in the frames or housings will be fastened in a closed position.

Final Run Test 

Every Generator repaired is tested for proper electrical and mechanical operation, as long as an adequate prime mover is available . low-medVoltage, Speed, Bearing temperature, and Vibration are closely monitored and documented.  Generators are Run tested at minimum of 60 minutes duration at the rated voltage and until the temperature of the bearings have stabilized (+/- 1°C over 15 minutes). A maximum temperature of 150°F on babbitt bearings shall not be exceeded (unless bearing manufacturer specifies otherwise). On antifriction bearings and on Generators with a cooling fan, the bearing housing temperature should not exceed 30°F above ambient temperature for oil lubrication, and 50°F above ambient for grease lubrication. On units without external cooling fans, the bearing housing temperature should not exceed 50°F above ambient. At no time should the temperature exceed the drop test temperature of the lubricant. A written record of all tests and inspection results will be available to the user upon completion of repairs.

On-site Generator Repair and Maintenance services

  • Electrical repairs

Repair or replacement of contactors, regulators and timers, etc.

  • Troubleshooting

Troubleshooting & repair of unexpected generator malfunctions.

  • Generator Inspection & Maintenance Plans

EMX performs a comprehensive inspection of the emergency power supply system following NFPA 110 guidelines, as well as the requirements of the NEC Article 701 for Required Standby Systems and can make all needed repairs. This inspection covers all the systems of the lubricating, air, fuel, cooling, exhaust, battery, generator, generator controls and safety system, room air inlet and exhaust. Our inspectors are professional and reliable and provide you with a full equipment evaluation including condition monitoring, inspection reporting, and operational testing.

Generator Maintenance Plan Inspection

• Engine Lubrication Systems: Inspect engine for leaks; oil and filters changedTypical-diesel-maintenance-schedule
• Engine Air Cleaners: Wet type: clean and change oil yearly. Dry Type: Clean or replace filter.
• Ignition Systems: Check magneto and replace spark plugs as needed.
• Governor: Check and set speed, sensitivity and oil level.
• Engine Cooling System: Check general condition, anti-freeze, coolant level, belts and hoses.
• Engine Electric System: Test battery and clean battery posts and cables.
• Engine Fuel System: Inspect for leaks. Check all connections and fuel lines.
• Engine Exhaust System: Check for leaks and corrosion.
• Instrumentation: Check all instruments for proper operation.
• Timers and Relays: Check for proper operation.
• Safety Circuits and Alarm Systems: Check for proper operation
• Engine: Run loaded when possible

Generator Sets

  • Cummins Power Generation
  • ASCO
  • Blue Star
  • Generac
  • General Electric
  • Kohler
  • Kato
  • Perkins
  • Zenith
  • Marathon

Transfer Switches and Switchgearsimages

  • Cummins Power Generation
  • Generac
  • ASCO
  • Eaton
  • General Electric
  • Zenith


Our Generator Service personnel are MSHA trained for safe work practices. They make an excellent resource to supplement your existing maintenance team and provide the specialized service you expect from EMX Electro-Mechanical.

Got a Question! Contact us at 856-362-4553 or email to