Larry JohnsonGenerator Specialist Generator Division
After High School and studying two years in electrical theory, I started in the electrical field working at JP Stevens & Co. I was working with the electrical group on maintaining AC industrial units for the plant. Then I started working with Electric Services and Repairs of Rock Hill, SC, a local AC/DC motor repair center. In the winter of 1984, an opportunity opened up at GE® and I continued to further my training in all aspects of generator repair and design. One significant activity was on the liquid-cooled stator rewind short cycle program, including tooling redesigns for reduced cycle times for rewinds and later on for repairs and schedule reduction, as well as, leader training in switchgear overhauls, relays, and MCC (Motor Control Centers). The next chapter began in 1999 with MD&A. Once hired, I was given the opportunity as a Generator Specialist, training on project management, leadership, team building, and overseeing domestic and international projects.
What do you do here at MD&A?
As a Generator Specialist, my responsibilities are mainly onsite projects, including performing electrical testing of generators, overseeing large-scale rewinds, and performing consultant services to help our customers better decide what type of generator repairs are needed. With my 35+ years of knowledge in power generation, I also assist with quotations and associated scopes of work.
What is the most interesting challenge you have encountered with a Generator Field or Stator?
I had an international project on a stator that started with core iron repairs. We performed roughly 50 localized core iron damage repairs. While making those repairs, we found the stator series knuckles with incorrect insulation. We had to strip the old insulation and install the proper type (Bake Tape). The challenge was building a bake oven for the stator end windings and a heater unit to complete the knuckle repairs; after 3-4 days of working with the local suppliers to get the materials we needed, we had what was required to complete the process.
What are the normal Electrical Tests for a Generator?
There are many electrical tests to perform when it comes to generators, exciters, etc. The normal stator tests are the (DLRO)-Resistance test and the (PI)- Polarization index, which is a 10min megger test, DC leakage test of the stator windings, Doble testing. Typical on the field rotor is a (DLRO) Resistance,(PI) Megger, (RSO), and the Impedance test. The type of issues a generator may have will determine the best measure of testing that should be done. What I have listed above is the normal starting point.
Why is my endwindings showing movement or dusting?
The main reason a stator winding starts moving is from two key components; a loose wedge system can turn into loose winding at the ends & second a loose blocking system tied to the coils to prevent movement or weak ties on the endwindings.
What do you like to do in your spare time?
I enjoy spending my free time at Church, camping, and building things.