Chuck Yung
Senior Technical Support Specialist
Electrical Apparatus Service Association
St. Louis, MO
In the paper "Time- and Money-Saving Devices for the Service Center," presented at the EASA Convention 2015, Chuck Yung shares practical tips and innovative ideas to help service centers improve productivity and save money. With the high costs of modern testing equipment, such as surge testers and test panels, it is essential for service centers to find cost-effective solutions. This paper compiles valuable insights from EASA members and others in similar industries, offering a range of tips to enhance efficiency and reduce expenses.
One of the key areas covered is electrical testing. Yung suggests building a large shop growler using a scrap stator or a DC field and pole, which can serve as a custom growler for testing rotors. For performing AC voltage drop tests on machines with inaccessible inter-coil jumpers, he recommends using a "pick up coil" made from a solenoid coil or a small field coil. Armature testing can be simplified by using the end bracket with the brush rigging to perform a voltage drop test between bars, avoiding the need for expensive devices.
Core loss testing can be enhanced by using a surplus 400 Hz generator, which quickly reveals hot spots. Welding machines can serve as low voltage, high current test panels for drop testing interpoles or large synchronous field coils. Additionally, a wound rotor motor can be repurposed as a variable output autotransformer or a variable frequency power supply, providing versatile testing capabilities.
In the machining section, Yung highlights the use of expandable collets to grip the inside diameter of shaft clearance fits, making it faster and safer to handle end brackets. For balancing, he suggests creating a stepped shaft from a scrap shaft to hold commonly balanced fans or impellers. To reduce eye strain and mistakes when chamfering a commutator, a page magnifier mounted on a magnetic base can be used.
For aluminum rotor repairs, Yung offers an alternative to rebarring by drilling through the end ring and inserting a replacement bar, which can be MIG welded to the end ring. This method allows for quick repairs without the need for a complete rebar.
Cleaning processes can be improved with the use of automatic parts washers, which offer significant labor savings and environmental benefits. Dry ice cleaning is recommended for its portability and eco-friendliness, especially for on-site motor cleaning. For removing varnish from machine surfaces, an oxygen-rich flame from a cutting torch can be used to burn off the resin without overheating the part.
Yung also provides tips for cleaning heat exchangers, such as using bottle brushes or taking radiator-type heat exchangers to a local radiator shop for boiling out. Painting the stator core a bright color improves visibility for winders, reducing eye strain and the chance of errors. An inexpensive pull-down shade can protect winding insulation materials from contamination.
Finally, Yung advises against building an induction bearing heater, as it is more cost-effective to purchase one. However, he suggests using the heater to test coils for shorted turns. For replacement parts, local marinas or sheet metal shops can fabricate air baffles and fan covers when the original manufacturer is unavailable.
Key Points Covered:
- Electrical testing tips, including building custom growlers and using pick up coils
- Enhancing core loss testing with surplus 400 Hz generators
- Using welding machines and wound rotor motors for versatile testing
- Machining tips for handling end brackets and balancing
- Alternative methods for aluminum rotor repairs
- Cleaning processes with automatic parts washers and dry ice cleaning
- Tips for cleaning heat exchangers and painting stator cores
- Advice on purchasing induction bearing heaters and sourcing replacement parts
Key Takeaways:
- Cost-effective solutions can significantly improve productivity and reduce expenses in service centers.
- Custom-built tools and repurposed equipment can enhance testing capabilities.
- Proper cleaning and maintenance practices are essential for efficient operations.
- Investing in the right equipment, such as induction bearing heaters, can save time and money in the long run.
- Local resources, such as marinas and sheet metal shops, can provide valuable support for sourcing replacement parts.
To read the full technical paper and view the slides, download the PDF below.
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