Troubleshooting “Little Jake”

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Troubleshooting “Little Jake”
Stepping through the troubleshooting and repair process on a vintage Jacobs wind turbine.
Little Jake needed to come down for repair.
Based on troubleshooting tests, Little Jake needed to come down for repair.
Little Jake’s tail was manually furled out of the wind
Little Jake’s tail was manually furled out of the wind so tower wiring could be checked.
The controller box
The controller box was tested and diagnosed.
Diversion controller, dump loads, and DC panel.
Diversion controller, dump loads, and DC panel.
RE systems’ balance of system (BOS) components
The RE systems’ balance of system (BOS) components, including the charge controller, battery bank, inverters, and DC and AC load power centers.
A megaohmeter (megger)
A megaohmeter (megger) was used to test the THWN conductor insulation.
Yaw slip-ring brushes.
Yaw slip-ring brushes.
Yaw slip rings.
Yaw slip rings.
A high-potential (hipot) tester
Testing for shorts from the conductors to the metal tower was accomplished with a high-potential (hipot) tester.
Testing in the shop
Testing in the shop revealed an internal short—a short from wire to wire—in the armature windings.
Testing in the shop
Testing in the shop revealed an internal short—a short from wire to wire—in the armature windings.
The front end of the generator
The front end of the generator. The blades would be attached to the long shaft.
The rewound armature.
The rewound armature.
Troubleshooting “Little Jake”
Little Jake needed to come down for repair.
Little Jake’s tail was manually furled out of the wind
The controller box
Diversion controller, dump loads, and DC panel.
RE systems’ balance of system (BOS) components
A megaohmeter (megger)
Yaw slip-ring brushes.
Yaw slip rings.
A high-potential (hipot) tester
Testing in the shop
Testing in the shop
The front end of the generator
The rewound armature.

One of the three wind turbines at the Midwest Renewable Energy Association (MREA) in Custer, Wisconsin, is a vintage machine that has its roots in the days before rural electrification. Made in 1946 by Jacobs Wind Electric, the 3.6 kW turbine was originally marketed to homes and farms that had no access to the electrical grid, and was used to charge batteries to run low-voltage DC lights and appliances.

In the 1980s, wind energy expert and MREA founding member Mick Sagrillo brought this turbine to his renewable energy shop in Wisconsin, where he remanufactured nearly every component. He donated the machine, top tower section, and controller to the MREA and led an installation workshop in July 2000 to erect and commission the system. Here at the MREA, it’s affectionately called the “Little Jake,” so we don’t confuse it with the 20 kW Wind Turbine Industries Corp. (WTIC) wind turbine (also an original Jacobs design) on site, which was recently modified into a 17.5 kW machine.

Little Jake is a 600-pound, upwind machine (meaning that the blades face the wind ahead of the generator) with a 14-foot-rotor diameter and a swept area of 154 square feet. The three blades are made of robust Sitka spruce, and finished with high-quality automotive paint and leading-edge tape, used on helicopter blades for durability. In a 24 mph wind, the rotor rpm is 325, and the system produces 3,600 watts. Little Jake will cut in at 6 mph and start to govern at 27 mph. In high winds, the pitch-control governing system automatically allows the blades to twist from their optimum aerodynamic orientation, “shedding” wind to protect the machine. For user/technician shutdown, the manual furling mechanism folds the tail, which pulls the blades parallel to the wind. It is activated at ground level via a chain that runs from the tail, down the tower, through a pulley, and to a hand crank.

This Jake is a DC generator, quite unlike a modern three-phase permanent-magnet alternator. The field poles and windings contain a residual magnetic field within their iron cores. When the turbine blades are driven by the wind and the armature rotates within the magnetic field, current is induced into the armature, and brushes that ride on the commutator deliver that power through a slip-ring assembly (so the turbine can freely yaw without twisting wires) and down the tower to the balance of system components. This machine is battery-based, so the controller delivers the DC voltage from the generator to a battery bank and diversion loads. If the batteries are full, the power is routed to a load center and to the electrical grid through an OutBack inverter to provide utility-intertied and backup energy for the MREA.

After almost 11 years in service, MREA staff noticed that although Little Jake was spinning, no voltage or current was displayed on the controller—the system wasn’t delivering power. Initial investigations showed no signs of open or shorted wires, failed diodes, blown fuses, nor tripped breakers. Little Jake needed a more thorough inspection and, fortunately, the organization’s July wind turbine maintenance and repair course was only a few weeks away. MREA small wind instructor Cris Folk and I were excited to have the opportunity to teach troubleshooting techniques on an installed machine with a real-world problem.

Troubleshooting Little Jake

The key to successful troubleshooting is to isolate and test individual system components and understand the order in which they operate. Cris and I would rely on this rather than “swaptronics”—the replacing of components until the system eventually worked again. Swaptronics is a sorry excuse for troubleshooting—plus we didn’t have spare parts to swap. We would have shared with the students the manual and/or schematics for the system—if we had any such documentation. But other than Mick’s drawings and descriptions, we had nothing.

Any component or portion of the system tested and deemed “good” would be scratched off our list of possible causes. This process of elimination would point us toward the problem and its solution. We broke the system down into three areas:

Balance of System (BOS)

  • Controller voltage checks
  • Inverter voltage checks
  • Battery bank voltage checks
  • Verify correct setpoints in the inverter and diversion loads

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Comments (1)

Lindsey Roke's picture

I was interested in the trouble-shooting approach.
It appears to have followed what we might call “the aardvark method”.
(“I am thinking of a word in the dictionary, what is it?”
“Is it aardvark?”
“No”
“Is it aardwolf?”
“No”
Etc.)
This method will eventually find a fault but it but it is not the fastest – and without due care has the potential to introduce more problems if (for example) connections are not done up again correctly.
Here in New Zealand I work for an appliance manufacturer (Fisher & Paykel Appliances Ltd.). In managing production engineering I have always been intrigued by various approaches to trouble shooting. We learned a great deal from the late Dorian Shainin when we had him here running some training sessions for us. (Look him up on the web is you are not familiar with him.) The technique he would propose for the dictionary would find any word with about 17 questions requiring just yes/no answers. (Find the middle page and ask if the word is before that page. Then go to the quarter or three-quarter point as appropriate. 11 questions will get you to the right page in a dictionary with up to 2048 pages. The next question gets you to the right column. Assuming there are no more than 32 words in a column, 5 more questions will get you to the right word.)
I recall one factory break-down where the photocell sensor was supposed to detect a cabinet on the assembly line, send a signal to a microprocessor controller, which in turn was supposed to drive a solid state relay which switched a hydraulic valve that operated a piston that did something useful. The problem was that when the cabinet went in front of the photocell the useful action didn’t happen. While I could have started by checking that the photocell was working, it was much quicker to repeatedly “cut the problem in half”. Because we had indicator lights across the electrical connections on hydraulic solenoids, (put there when the equipment was installed for just such trouble-shooting) the first check was to see if there was power getting to the solenoid when the photocell was triggered, etc. etc. (Without the indicator lights, the same thing could have been done with a meter – but when an assembly line is stopped, time is of the essence.).
You can bend the rules a bit if there is a very easy point to check that is not mid-way through the problem – or if there are other clues as to where to start looking.
I have learned that, if a piece of equipment has been operating OK and it stops, unless somebody has already had a go at trouble-shooting it by swapping components in and out before you arrive, it will very very rarely have more than one fault.
My objective, when called to an intractable malfunction, is to determine which component is faulty, get the tradesmen to replace it and walk away with confidence that the machine would work when they have done so.
While the mid-point of the Jacobs system in the article might be the input to the slip-rings, to save climbing the tower, checking first whether or not there was a voltage at the bottom would have isolated the problem to either the Balance of system and wiring to it from the tower or – to the generator, slip-rings and tower wiring. The next check at the generator terminals would have put the fault in the generator or in the slip rings and tower wiring etc.
(I’m not decrying checking such things as the brush and slip-ring condition while up the tower – but as maintenance tasks not as trouble-shooting in this case.)

Shainin, in my opinion was better (at least in this area) than either Joe Juran or Edward Deming – but not so well known, probably because he was better at solving problems than writing books.
I trust this might be useful.

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