Presented by Kevin Alewine, Application Engineer, Shermco Industries
Most current levels of Condition monitoring tell little about the generators in wind turbines other than bearing and stator temperatures but there are a lot of things to check to help keep them in good condition. Kevin Alewine, Director of Renewable Energy Services with electrical services and generator remanufacturer Shermco Industries, will discuss generator maintenance at the upcoming WindTech 2012 in Sweetwater, Texas.
“Most techs only see the outside of a generator so we’ll show what’s on the inside, the materials used to manufacture the electrical circuits, discuss why they are chosen, and the different styles,” says Alewine. He’ll also review the online and offline testing that can be done on a generator. Some of it is standard testing that a wind turbine technician might do frequently, along with the next level of testing when problems are suspected. “I’ll have some example test reports to illustrate the value of good diagnostic testing for equipment reliability,” he says.
The discussion will go through common tests that could flag something serious. “We’ll cover the general failure modes, common mechanical and electrical ones, and show the failure statistics to the areas they should pay attention to,” adds Alewine.
Normally, technicians will have their own test report to work from. “Say they are doing a test, such as for insulation resistance on the windings. All it tells them is whether or not the windings are wet, dirty, or both, and whether the generator is safe to energize. We’ll cover what to do next if a greater problem is suspected.
The techs would have their own in-house report to work from. “It’s usually a checklist for use up tower. The report tells them to check the brushes and other items, and do a megger (insulation resistance) check to see what the windings are like. If they find something, that could initiate a second level of testing. We’ll discuss that too,” he says. An offline automated surge test, one frequently encountered, runs through a whole battery of tests that provides about a 20-page report that is a good indicator of the functioning condition of the machine.
If the sequence is not automated, the techs would fill out a form that they can work from pdf on a laptop. But if there is a problem, we’ll look at the next step for testing and maintenance.
Wind turbine generators are typically low voltage machines with high amps. A common problem is that they generate circular and transient currents in the shaft. If these go to ground through the bearing, they can be destructive. A lot of generators are double-fed induction designs with carbon brushes, so when you check the brushes, also check the grounding circuit brush. A generator might also have ceramic or insulated bearings that are items to check as well. There are lots of little things to check.
WindTech 2012 will be held in Sweetwater, Texas, November 29 and 30. Register here:
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