Simo motors successfully solved the rotor open-circuit fault of a mining company's JR series wire-wound motor.

I. Fault Background: Production Interruption, Urgent Assistance Requested

Customer Information:

• Client OrganizationA large mining group's mineral processing plant (name withheld at client's request)
• Equipment TypeJR137-4 Wound-rotor Induction Motor
• Key ParametersRated power: 220 kW Rated voltage: 6 kV Rated rotor voltage: 275 V Rotational speed: 1480 r/min
• application scenarioCore Ball Mill Drive Equipment
• Fault Symptoms：
  • Sudden shutdown during operation; motor fails to restart.
  • The electronic control system displays "Rotor circuit abnormality."
  • The slip ring area exhibits distinct discharge marks accompanied by a burning smell.

II. In-Depth Diagnosis: Pinpointing the Fault Location

Simo motorsUpon receiving the service request, the technical team responded immediately and arrived on-site within 4 hours to conduct system diagnostics:

1. Preliminary Detection and Analysis

• Using a multimeter to test the three-phase windings of the rotor, an open circuit was detected in the B-phase winding.
• Insulation Resistance Measurement: Rotor winding insulation resistance to ground is 0.8 MΩ (standard requirement ≥ 1 MΩ).
• Inspecting the slip ring assembly: One of the slip rings was found to have severe surface burn damage.

2. Precision Diagnostic Localization

• Perform scanning inspection using a winding interturn tester
• Performing temperature distribution analysis on rotor windings using a thermal imaging camera
• Fault Pinpointing：
  1. The lead wire of the sixth winding in phase B of the rotor winding has broken.
  2. The welded joint between the slip ring and the winding has burned out.
  3. The slip ring surface exhibits uneven wear reaching 1.2 mm.

III. Professional Maintenance Plan and Implementation

Based on the diagnostic results, we have developed a specialized repair plan:

1. Rotor Winding Repair

• Detailed TeardownCarefully remove the faulty coil using specialized tools, taking care not to damage the iron core.
• Winding Repair: Rewind the coil to the original specifications, using F-class insulation material to enhance the heat resistance rating.
• Welding ProcessUse silver-phosphorus copper solder to ensure reliable and secure connections.

2. Slip Ring Assembly Repair

• precision machiningPerform precision turning on the slip ring surface to restore standard surface finish.
• Carbon Brush ReplacementReplace all carbon brushes and adjust spring pressure to standard value.
• Enhanced InsulationInstall a reinforced insulation sleeve between the slip ring and the shaft.

3. Professional Process Control

• Dynamic Balancing CalibrationCalibrated on a dedicated balancing machine, residual unbalance < 1.0 g·mm/kg
• Vacuum impregnation: Utilizing the VPI process to ensure thorough penetration of the insulating varnish
• High-temperature curing: Strictly follow the process curve for temperature ramping and curing.

IV. Maintenance results and customer value

1. Verification of Repair Effectiveness

• The test run after repair was successful on the first attempt.
• Rotor three-phase DC resistance balance ≤ 1%
• Insulation resistance restored to over 500 MΩ
• Parameters such as temperature rise and vibration exceed standard requirements.

2. Value Creation

• Rapid resumption of productionRepairs completed within 36 hours, reducing production downtime losses by approximately 800,000 yuan.
• Performance Enhancement：
  • Motor efficiency improved by 3.21%
  • Annual electricity savings are projected to reach approximately 45,000 kilowatt-hours.
  • Carbon brush lifespan extended to twice the original duration
• Management OptimizationAssist in establishing a dedicated maintenance plan for the rotor system.

V. Case Summary and Technical Extension

1. Key Points for Maintenance of JR Series Motors

• Wound-rotor motors require particular attention to the coordination between the rotor windings and the slip ring system.
• Regularly inspect the wear condition of carbon brushes and spring pressure.
• Monitor the formation status of the oxide film on the surface of the slip ring

2. Preventive Maintenance Recommendations

• Daily Inspection：
  • Check the carbon brush wear daily.
  • Measure the insulation resistance of the rotor windings weekly.
  • Inspect the surface condition of slip rings monthly.
• Professional Maintenance：
  • Perform rotor dynamic balancing verification every six months.
  • Annual winding interturn insulation testing
  • Establish a Rotor System Operation Record

VI. Simo Motor's Professional Advantages

This case study demonstrates Simo Motor's expertise in the repair of wound-rotor motors:

1. Professional equipment：
   • Equipped with large dynamic balancing machines and VPI impregnation equipment
   • Equipped with professional winding machines and testing instruments
2. Technical Team：
   • With over 20 years of experienceWound Motor RepairExperience
   • Holders of Electromechanical Professional Qualification Certification
3. Process Standards：
   • Strictly implement the ISO 9001 Quality Management System
   • Adopting internal process standards that exceed national standards