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Items filtered by date: October 2016

The Application: Pitch Drive Amplifier in GE 1.5 ESS Wind Turbines

Editor’s Note: This Blog is Part One in a Five-Part Series about the Most Failure-Prone Electrical Systems in Wind Turbines That PSI Repair Most Frequently Services

If you read our recent article about electrical failures in wind turbines published in North American Clean Energy, you’ll know that electrical system failures are responsible for 50% of all Wind Turbine (WT) downtime according to Reliawind report data.


What’s surprising is that the system reported to have the single highest failure rate isn’t the power converter – and, even more surprising, it isn’t even technically considered an “electrical” system by their classification and therefore isn’t included in that 50% mark (making that figure an underestimation).

GE-Wind-Turbine-H-Bridge-Hub-ConverterThe Pitch System – which is located in the turbine hub and is designed to regulate rotor blade angles in order to maximize wind power production – holds the honor of having highest stand-alone rate of failure in WTs. With a 23% contribution to overall downtime across multiple WT manufacturers, it edges out the second most failure-prone part, the power converter, by 5%.

Since WT failures increase exponentially after 10 years in service, it’s no surprise that turbines installed around 2005 are especially vulnerable to Pitch System failure.

One of the most common examples of this in practice is the Pitch Drive Amplifier found in the Pitch System of GE’s 1.5 ESS WT, a popular turbine for many wind farms in the mid-to-late 2000s with about 12,000 in operation worldwide. We refer to this Pitch Drive Amplifier system as the GE H-Bridge / Hub Converter.

Wind-Turbine-Pitch-Drive-Amplifier-FailureTemperature, vibration, and humidity are three of the most common causes of failure for electrical components, with temperature being the dominant stressor causing most stoppages. We found that the GE Pitch Drive Amplifier was no different in this respect.

After a root cause analysis study of 50 Pitch Drive Amplifier units—many of which revealed irreparable damage to circuit boards (see right for an example of this)—we concluded that 85% of the pitch drive failures were due to capacitor breakdowns.

Wind speed variability, sun, capacitor losses, and switching losses caused the capacitors to overheat internally and expel electrolytic fluid, destroying the driver board. In addition, transistor failures were due to improper switching frequencies and speeds.

Based on the findings of our failure analysis and subsequent results of a 6-month field test, we designed a new and improved driver board that prevented failures from high heat loads and stripped ground screws.

PSI’s custom upgrade included the following preventative repair actions:

  • Replacing the OEM Switching Driver with PSI Repair’s own part
  • Installing upgraded capacitors
  • Using steel inserts to create more durable ground lug threads
  • Enhancing the transistors to match the switching frequency

This upgrade resulted in an 81% Reduction in year over-year failures (using a 4-year analysis) and cost-savings of approximately $417,000 on labor, material and lost revenue:


All told, we’ve upgraded and installed over 3,000 of these Pitch Drive Amplifier systems to date.

PSI Repair has helped the wind industry by repairing over 28,000 wind components over the last 5 years. So if your wind turbine is aging or frequently failing because of electrical, hydraulic, or mechanical faults, call us—we’ll get to the bottom of these issues so that your turbine runs faster and better than ever. You can also visit our Wind Turbine Component Repair page for more information about our WT repair and engineering services. 



Published in Blog

It’s hard to overstate the importance of Wind Turbine performance on the future of the Wind Energy industry and, in many respects, the future of power generation and clean energy in the United States.

If the Department of Energy is right, wind farms will generate 20% of U.S. electricity by 2030 and 35% by 2050 (up from just 5% today). This shift would spell massive change around the world, starting with American shoreline views and extending to the stability of OPEC economies.

But there’s one key variable that will define whether the 35%-by-2015 scenario becomes reality or remains a pipedream. Everything hinges on Wind Turbine (WT) Reliability, a measurement of the availability, performance, and output of turbines.

Recent research puts WT O&M costs between $9.8 to $21 per megawatt-hour, with the average GE 1.5 MW turbine producing about 3,285,000 kWh (or 3,285 mWh) of wind power output annually. This is consistent with older research placing average O&M costs around $50,000 per year per turbine for on-shore WTs (O&M costs at least double on off-shore farms).

Downtime and unscheduled maintenance are such serious threats to the profitability and survival of the industry that GE is betting the farm on the development of predictive maintenance software that identifies “early warning signals [that a part] needs repair, before it breaks down.”

We’re excited to see GE’s Predix platform applied to WTs down the road. In the meantime, though, there are about 50,000 installed WTs in the US, and a huge number of them are vulnerable to the same design flaws (and environmental stressors) that trigger outages and protracted downtime.

We’ve been monitoring and servicing these flaws for the largest wind farms in the United States since 2009. From simple repairs to component remanufacturing and product upgrades, we provide the widest range of economical repair and engineering services for the wind energy industry.

We help O&M managers substantially reduce long-term costs by helping them diagnose, anticipate, and address the root cause of WT failures before high-cost unplanned or emergency field service is required. And in our experience, electrical failures are the most chronic and costliest problem affecting WTs in the long run. As you’ll read in this article, electrical systems cause at least 50% of total WT downtime, and if you include the Pitch and Yaw Systems (which both contain electrical parts) in this estimate, the figure rises to a staggering 80%.

Subsequently, longevity is an important factor to consider when choosing a repair company—there’s a reason why some repair providers have been operating and growing for several decades and others stagnate after a few years in business.

Of all the electrical parts we repair, five in particular stand out for the sheer frequency that we receive them. They are:

    1. GE H-Bridge/Hub Converter
    2. GE Line IGBT
    3. GE Rotor IGBT
    4. GE AEBI Card
    5. Vestas VRCC3
    We’ve decided to write a blog post on each of the five parts mentioned above – examining why they fail and how we fix them – in the near future.

Editor’s note: hyperlinks will be added to each line above as the blogs are published

We bridge the gap when OEM warranties have expired on these parts and they begin to sputter or fail outright. Our repair actions include: removing and replacing stressed parts; improving legacy design with newer, more reliable technology; remanufacturing unsalvageable or obsolete components; and manufacturing custom-designed products. We use the latest diagnostic equipment to detect failures in these parts down to the microchip level.

Contact us toll-free at 800-325-4774 or visit to learn more about our repair capabilities. To learn more about electrical failures in wind turbines, click here.

Published in Blog

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