Chuck Yung
Senior Technical Support Specialist
Electrical Apparatus Service Association
St. Louis, MO
The paper "2-Pole AC Repair Tips" by Chuck Yung, presented at the EASA Convention 2008, addresses the unique challenges and solutions associated with repairing 2-pole motors. These motors are known for their critical alignment requirements, susceptibility to vibration, and specific winding difficulties. The paper compiles common problems encountered during the repair of 2-pole motors and offers practical solutions to treat these issues as opportunities rather than challenges.
One of the primary challenges with 2-pole motors is the winding process. Due to their high rotational speeds, these motors have small bore diameters and wide coil pitches, making coil insertion difficult. The paper emphasizes the importance of selecting the correct coil pitch to avoid slot spatial harmonics, which can negatively impact motor performance. It provides guidelines for avoiding coil pitches that result in significant harmonics and suggests increasing the coil pitch to reduce winding losses and improve efficiency.
Axial hunting, or the chronic axial movement of the rotor, is another issue with 2-pole motors. This phenomenon is caused by weak magnetic centering forces, which are proportional to the number of poles. The paper explains that factors such as the position of the stator core ends, airgap, shaft level, rotor bar skew, and aerodynamic forces influence magnetic centering. Solutions include ensuring the shaft is level, correcting tapered airgaps, and adjusting baffles to balance aerodynamic forces.
The paper also addresses vibration issues during testing, highlighting the importance of proper base support and alignment. It explains that high vertical vibration readings can indicate a soft foot or twisted frame, and emphasizes the need for shimming to support the bulkheads of the motor frame. Proper handling and lifting techniques are crucial to avoid frame distortion, which can lead to vibration problems.
Oil leaks are a common problem in 2-pole motors, often caused by the venturi effect drawing air through the labyrinth seal. The paper suggests venting the inner labyrinth seal to the exterior of the motor to prevent air from passing through the bearing chamber and carrying oil with it. This solution helps to eliminate oil leaks and improve motor reliability.
Overall, the paper provides a comprehensive guide to addressing the unique challenges of 2-pole motor repair, offering practical solutions to improve performance, reduce vibration, and prevent oil leaks.
Key Points Covered:
- Winding difficulties and the importance of correct coil pitch selection
- Axial hunting and weak magnetic centering forces
- Vibration issues and the importance of proper base support and alignment
- Solutions for oil leaks caused by the venturi effect
- Practical tips for handling and lifting to avoid frame distortion
Key Takeaways:
- Correct coil pitch selection is crucial to avoid slot spatial harmonics and improve motor efficiency.
- Ensuring the shaft is level and correcting tapered airgaps can prevent axial hunting.
- Proper base support and alignment are essential to minimize vibration.
- Venting the inner labyrinth seal to the exterior can prevent oil leaks.
- Proper handling and lifting techniques are necessary to avoid frame distortion and subsequent vibration issues.
LOGIN TO DOWNLOAD THE CONVENTION PRESENTATION
Related Reference and Training Materials
Print
