AC  Motor Repair & Rewinding Services

Electric motors are among the highest reliability incident reports for many companies. This leads to a continual cycle of costly electric motor repair, inconsistent quality and unplanned downtime factors that can hurt your bottom line. We not only repair and refurbish your motor but to provide root cause failure analysis on why it has failed. We consistently provide electric motor repairs and refurbishments that are better than new motors!

  Our comprehensive Electric Motor Service, repairs motors, 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 AC Motor Repair services include:

  • Reconditioning – Repair, reconditioning, and adjustment of the Electric Motor• Stator components’ parts are thoroughly cleaned and baked dry. Replacement of Bearings, Seals and any auxillary componants, as required.
  • Rewinding –Complete refurbishing of the Electric Motor• 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.
  • ModificationsWe offer application design and assistance, plus the capabilities of modification of New Electric Motors and Generators to meet your specific requirements.
  • Testing – AC Motors are tested using non-destructive winding analysis and testing and test run for proper electrical and mechanical operation. Voltage, Current, Bearing temperature, and Vibration are closely monitored and documented.
We know Motors! Contact us for a Motor Repair Quote, a Replacement Motor, or Predictive Maintenance Plans.

Repair Service for all types of AC Motors of the following designs:

•  Induction Motors                                                 •  Wound-Rotor (Slip-Ring) Motors Teco Vertical
 Synchronous Motors                                          •  Commutator Motors
•  Inverter Duty Motors                                         •  Cooling Tower Motors  
•  Hoist/Crane Motors                                            •  Spindle Motors
•  Printing Press Motors                                        •  Specialty Motors 
•  Explosion-Proof Motors                                    •  Vertical Hollow Shaft Pump Motors
  Fan & Blower Motors                                             Submersible Pump Motors 
•  Conveyor Motors                                                  •  Eddy Current Clutches
•  Washdown Duty Motors                                    •  Chemical Processing Motors
•  Shaker Duty Motors                                             •  Gearmotors

AC Electric Motors are used in applications from a small, special purpose apparatus to those driving large-scale industrial machinery. The most common type of AC Electric Motor used in Industry is the Asynchronous Motor or (as more commonly referred to) Induction Motor.

The Induction motor is an AC Electric Motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor as are found in Universal, DC Motor-Cutaway1Motors and Synchronous Motors. An induction motor’s rotor can be either wound type or squirrel-cage type. Three-phase squirrel-cage induction motors are widely used in industrial drives because they are rugged, reliable and economical. Induction motors are increasingly being used with Variable-Frequency Drives (VFDs) in variable-speed service. EMX Motor Repair Shop has the expertise to design a VFD package which can offer especially important energy savings opportunities for existing and prospective induction motors.  Typical uses include constant and variable- torque Centrifugal Fan, Pump and Compressor load applications. EMX Motor Repair Shop offers the capability, reliability, experience, and customer service needed to completely refurbish motors, as well as provide expert Motor Drive solutions.

Every aspect of our AC Motor Repair shop, from electric motor rewinding to electric motor part repair, is performed under the stringent quality standards. As a reflection of our uncompromising commitment to customer satisfaction, all of EMX Electric Motors Service work is 100% guaranteed.

 Incoming Inspection

EMX Motor Repair Shop performs a thorough appraisal of the motor’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 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. Digital Photographs of any abnormal conditions found are part of the appraisal process and inspection report. Our AC Motor 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: 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.

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 windings and the extent of repairs are determined by inspection and, as necessary, by testing. Stator 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, we 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.  Bars and end rings for amortisseur and squirrel cage windings are examined for evidence of defects.  Additional Testing may be required.

The Rotor is the second major electrical component to be appraised. Cleanliness, electric-motor-2laminations, vent spacers, slot tooth condition, and rub marks are checked as in the stator. Rotor laminations are checked for “coning” (separation of laminations, causing the length of the rotor to be greater at the outer diameter than it is at the shaft). Electric Motor 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 and 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 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.

Electric Motor Accessories, such as, capacitors are tested for rated capacitance, and subjected to a high-potential test. Capacitors are replaced if damaged. Short circuit devices, centrifugal mechanisms, switches, and starting relays are verified for electrical and mechanical operation at correct speed and voltage.  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.


EMX’ Shop Balancing Systems are designed to perform measurements of stacks_image_1428vibrations and calculations 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 Stator

Stator components’ parts are thoroughly cleaned by Steam cleaning, as 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 stator 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 10 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 Stator verses the cost of motor replacement.

In the event that Rewinding of Stator is the better choice in the repair of the Electric download statorMotor, 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 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. EMX Motor Repair Shop can redesign motors using computer aided motor redesign and assures that all Winding data is thoroughly reviewed for accuracy. The winding should maintain the same electrical characteristics as the original unless redesigned by agreement with, or at the instruction of, the customer. 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. AC Motors 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 Electric Motor 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 enclosurecases, shaft material will be replaced with 316 stainless or User approved material. Motors 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 AC Motor repaired is tested for proper electrical and mechanical operation. Voltage, Current, Bearing temperature, and Vibration are closely monitored and documented.  AC Motors 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 motors 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 motors 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. On squirrel-cage motors, we 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, we apply full primary voltage to stator and with rotor circuit open for a non-rotational test and measure rotor open circuit voltage and stator current. 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.

Completed apparatus will be externally cleaned and painted to specification. Shaft extensions are treated to prevent corrosion. Packaging and Transportation: After completion of the repair and testing, the machine will be packed in a manner suitable for the form of transport to be used. Packing and transport will be as arranged with the customer. Shaft is Blocked to prevent movement, depending on the type of machine, mode of transport and the distance to be traveled. Where blocking is used, it will be clearly identified. Oil-lubricated machines will be shipped without oil, and the need for lubricant clearly identified.

EMX Benefits

  • Complete Motor Inspection and Cleaning
  • Provide complete failure and documentation to determine the cause of Motor Failure
  • Comprehensive Bearing Inspection and new Bearing Installation
  • Digital pictures available for Inspection
  • Commissioning of your Equipment
  • Non-destructive winding analysis and testing
  • All Rewinds are made using Class “H” Insulation & Inverter Duty Wire
  • Utilize the best available technology in the repair of your Motor.
  • Treat your Motor problems with concern.
Got a Question! Contact us at 856-362-4553 or email to