## Generator Failures and Reactive Centrifugal Force

Oh, the laws of physics!

{Author’s Note. To avoid using the term “centrifugal force,” the author visited “Wikipedia, the free encyclopedia.” The first sentence in the article cautions, “Not to be confused with Centripetal force.” Who, on the other side of the Internet, knew we might be blurring those two concepts?}

When a mass (like the rotor of a motor or generator) is spinning, the force that causes the circular motion is aimed at the center, or axis, of the motion, and is called centripetal force. Mass wants to travel in a straight line, which would resemble a tangent to the rotor. However, Sir Isaac Newton’s Third Law of Motion tells us that the rotating mass exerts an equal force but in the opposite direction to the centripetal force. The term for this force is “reactive centrifugal force.”

The peripheral rotor speed is generally limited to the speed of sound, which is 1100 feet per second in dry air. That’s a lot of mass spinning pretty fast. It is the reactive centrifugal force that can manifest itself as rotor damage in wound rotor wind generators. You can see the devastating effects of this force in several videos we have recently posted on our YouTube Channel.

See the two videos on our YouTube Channel at http://www.youtube.com/user/BrithineeElectric. This article is demonstrated in “Examples of Generator Failure-Brithinee Electric and Examples of Generator Failure II.”  You can subscribe to our channel to be notified of new motor and control panel videos on this site.

The first video is an illustration of metal fatigue or welding failures that caused pieces of metal (about four inches across) to flair out from the reactive centrifugal force. This is an Elin one megawatt, Austrian-built, water-cooled wind generator The flared metal fragments become like knives that do amazing damage. The rotor of the generator cut holes into the windings of the stator causing massive shorts in the stator winding.

The second example is a Canterey two megawatt wound-rotor induction generator, made in Spain. The rotor banding has not held the winding on one end, and the resultant flared rotor coils has wiped out the stator winding. The wind powering the rotor blades may have gone over speed, causing the winding to flare outside its normal position, but in any case, the fiberglass banding tape, which opposes the reactive centrifugal force, failed. The rotor coils lifted up, creating a rotating saw which destroyed the stator windings.

Brithinee Electric makes an effort to establish the root cause of failure of each motor or generator we service. Only in this way can measures be devised that prevent a recurrence. Brithinee Innovation is our way of making significant improvements to the manufacturer’s original design, and a major reason we have a near-zero failure rate when rewinding wind generators.

Donald P. Brithinee

## History of Brithinee Electric: 50 Year Celebration

In some ways, the electric motor of 50 years ago was just like the original motor invented by General Electric for the first AC power station just up the valley from our facility. And it remains much the same since then, except for how we controlmotors. In the 1990’s, new computerized control systems gave us options on how we start, shut down, and change the speed of motors for specific uses.

In 1963, at the corner of Forth and N streets, we worked outside much of the time and repaired motors that ranged all the way back to the early days of the industry.  At first it was a job for each of us, then a way to pay for college, and graduate school. Despite advanced degrees in mathematics, we ended up staying put in the family business. In 1971 the family built a new building in our current location.

Wallace and Zora Brithinee founded the company in 1963. We grew enough to  purchase a parcel at  620 South Rancho Avenue in 1971 and constructed a new motor repair and sales facility there. The facility then measured 12,378 square feet on one acre. The building was expanded in 1978 to 19,178 square feet.

In 1992, Brithinee Electric expanded its motor sales and motor control operations at an additional facility acquired that year. This building added 14,500 square feet at 680 South Rancho Avenue to the operation. Housed in the new building was a large new motor inventory, and the new motor controls department. The computer chip had begun to impact the old electro-mechanical motor operation, and we began to build these new computerized controllers to increase efficiency and lower wear and tear on large motors.

Fifty years of Brithinee Quality

Our relentless pursuit of the perfect re-wind lead us to special partnerships with DuPont’s Advanced Fiber Systems’ through the first special marketing partnership in 2003. We found through over 20 years of use and testing that DuPont’s NOMEX insulation was more durable in tough operating environments. We made NOMEX our only insulator. Simultaneously, we began to test wire for toughness, flexibility, and electrical integrity over many years of use. This evolved to a special Quad-Build wire made by Essex. Large quantity orders required a large commitment, which we happily did because of the additional life added to the repaired motor. Adding specific high quality bearings and only the best resins, we created the four-step Brithinee Winding that today has a near zero failure rate when used together. All windings have left the shop with every critical component of the Brithinee Winding for some twenty years now. We are still waiting for our first failure.

New Facilities and Developments

While initial building plans began in 2004, actual construction for a major new addition waited until 2009 to add 19,910 square feet of premium workspace, for a total of 62,588 square feet.
– Mechanical engineer Bill Butek joined the staff in October 2003 to help innovate productivity improvements in the machines and fixtures for the motor remanufacturing process, as well as the controls department metal-working equipment.

2005 – Brithinee Electric began a relationship with UC Riverside’s Bourns College of Engineering, and, more specifically, with the Department of Mechanical Engineering. Our work was primarily with Professor V. Sundararajan and then-graduate student, Dr. Xin Xue (“Crystal”), who worked on wireless sensor technology for evaluating machinery condition. We also worked closely with senior undergraduate teams on their senior projects. Eventually, Wallace Brithinee joined the Board of Advisors for that department. In September of 2009, Dr. Xin Xue joined the firm to continue earlier wireless sensor research, plus partial discharge inception voltage testing.

November 2010 – Grand Opening of the new large motor repair facility.

Wally Brithinee is invited to return as a speaker to the 20th Annual Water Conference sponsored by Southern California Edison.

The conference takes place on September 11, 2013 in Irwindale at 9:30 a.m. Wally will present “Getting the Most from Your Electric Motor and Variable Frequency Drive.”

The class offers a look at future motor designs, protective devices, and tests. Workers in the water field are encouraged to attend because it will allow them to learn from leaders in the electric industry about the importance of making the right decision when specifying motors.

Wally will take a closer look at how motors and VFDs work, specifically which electrical, mechanical, and efficiency characteristics affect choices regarding proper replacements and good applications. Additionally, he will discuss current energy legislation and how these rules affect water professionals and the way plants are operated.

The class is worth 2.0 Contact Hours, California Department of Public Health.

Registration for the workshop is required. Attendance is free. Go to www.SCE.com/workshops to register.