NREL is a national laboratory of the U.S. Department of Energy, Office of Energy 

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Contract No. DE-AC36-08GO28308

Wind Turbine Generator System 

Safety and Function Test 

Report for the Entegrity EW50 

Wind Turbine

Joe Smith, Arlinda Huskey, Dave Jager, and 

Jerry Hur

National Renewable Energy Laboratory

Technical Report

NREL/TP-5000-56587

November 2012
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Contract No. DE-AC36-08GO28308

Wind Turbine Generator System 

Safety and Function Test 

Report for the Entegrity EW50

Wind Turbine

Joe Smith, Arlinda Huskey, Dave Jager, and 

Jerry Hur

National Renewable Energy Laboratory

Prepared under Task No. WE110308

Technical Report

NREL/TP-5000-56587

November 2012
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56587.docx Page 1 of 42

Safety and Function Test Report

for the

Entegrity EW50 Wind Turbine

Conducted for

Wind Energy Program

DOE/NREL

Conducted by

National Wind Technology Center

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

Joe Smith, Arlinda Huskey, Dave Jager, and Jerry Hur

7 November 2012
Page 2 of 42

Notice

This report was prepared by the National Renewable Energy Laboratory (NREL), operated for 

the United States Department of Energy (DOE) by the Alliance for Sustainable Energy, LLC 

(Alliance), as an account of work sponsored by the United States government. The test results 

documented in this report define the characteristics of the test article as configured and under 

the conditions tested.

THIS REPORT IS PROVIDED "AS IS" AND NEITHER THE GOVERNMENT, ALLIANCE, NREL 

NOR ANY OF THEIR EMPLOYEES, MAKES ANY WARRANTY, EXPRESS OR IMPLIED, 

INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 

PARTICULAR PURPOSE, OR ASSUMES ANY LEGAL LIABILITY OR RESPONSIBILITY FOR 

THE ACCURACY, COMPLETENESS, OR USEFULNESS OF ANY SUCH INFORMATION 

DISCLOSED IN THE REPORT, OR OF ANY APPARATUS, PRODUCT, OR PROCESS 

DISCLOSED, OR REPRESENTS THAT ITS USE WOULD NOT INFRINGE PRIVATELY 

OWNED RIGHTS. 

Neither Alliance nor the U. S. Government shall be liable for special, consequential or incidental 

damages. Reference herein to any specific commercial product, process, or service by trade 

name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its 

endorsement, recommendation, or favoring by the United States government or any agency 

thereof. The views and opinions of the authors expressed herein do not necessarily state or 

reflect those of the United States government or any agency thereof or Alliance. 

NREL is a DOE Laboratory, and as an adjunct of the United States government, cannot certify 

wind turbines. The information in this report is limited to NREL’s knowledge and understanding 

as of this date. 

NREL is accredited by the American Association for Laboratory Accreditation (A2LA) and the 

results shown in this test report have been determined in accordance with the NREL’s terms of 

accreditation unless stated otherwise in the report.

This report shall not be reproduced, except in full, without the written approval of Alliance or 

successor operator of NREL.

Approval By: __________________________________________________________

Arlinda Huskey, NREL Test Engineer Date

Review By: ___________________________________________________________

Jeroen van Dam, NREL Test Engineer Date
Page 3 of 42

Contents

List of Tables.................................................................................................................................................. 4

List of Figures ................................................................................................................................................ 5

1. Background............................................................................................................................................ 6

2. Test Objective ........................................................................................................................................ 6

3. Description of Test Turbine and Setup............................................................................................... 6

4. Instrumentation...................................................................................................................................... 9

5. Procedure ..............................................................................................................................................10

5.1. Control and Protection System Functions ...........................................................................................10

5.2. Personnel Safety Provisions..................................................................................................................11

5.3. Dynamic Behavior ...................................................................................................................................11

6. Results ...................................................................................................................................................11

6.1. Control and Protection System Functions ...........................................................................................11

6.2. Personnel Safety Provisions..................................................................................................................15

6.3. Dynamic Behavior ...................................................................................................................................17

6.4. Graphs and Plots of Turbine Responses.............................................................................................18

7. Exceptions.............................................................................................................................................27

7.1. Exceptions to the Standard....................................................................................................................27

7.2. Exceptions to NWTC Quality Assurance System...............................................................................27

8. Reference Document List....................................................................................................................28

A. Appendix - Equipment Calibration Sheets........................................................................................29
Page 4 of 42

List of Tables

Table 1 Test turbine configuration ................................................................................................7

Table 2 Equipment used in the power performance test ............................................................10
Page 5 of 42

List of Figures 

Figure 1 Entegrity EW50 test turbine at the NWTC (Photo by Joe Smith, NREL, PIX# 22243) ..8

Figure 2 Electrical single-line drawing of EW50 installation..........................................................9

Figure 3 Power response to wind speed, 1-minute data (Red–maxima, Green–minima, Blue–

average, Black–bin average) ..............................................................................................18

Figure 6 Resized power axis of Figure 3. (Red–maxima, Green–minima, Blue–average, Black–

bin average) ........................................................................................................................19

Figure 4 Normal operation in winds around rated wind speed, 1-Hz data ..................................19

Figure 5 Motor-up in winds around cut-in; 1-Hz data, showing 20 minutes ................................20

Figure 7 Upwind Power and Cp curves; 10-second data............................................................20

Figure 8 Rotor speed as a function of wind speed, bin averages in black; 1-minute data..........21

Figure 9 Control panel rotary switch to “Stop” winds above rated; 1-Hz data.............................21

Figure 10 Grid disconnect; without controller UPS, brakes act immediately; 1-Hz data.............22

Figure 11 Restart in winds greater than rated; generator over-speed detected (altered set 

points); 1-Hz data................................................................................................................22

Figure 12 Commanded “Stop” in gusty winds; tip brakes deployed for 30 seconds, then parking 

brake engages to stop rotor; 1-Hz data...............................................................................23

Figure 13 Control panel, showing a rotary switch (Photo by Joe Smith, NREL PIX# 22247) ....23

Figure 14 Signs on outer enclosure of control panel; “Notice” sticker added by NREL (Photo by 

Joe Smith, NREL PIX# 22244)............................................................................................24

Figure 15 EW50 lockable disconnect switch at data shed (Photo by Joe Smith, NREL PIX# 

22242).................................................................................................................................25

Figure 16 Warning sign on outer cover of EW50 control panel (Photo by Joe Smith, NREL PIX# 

22245).................................................................................................................................25

Figure 17 Bent yaw lock pin and cosmetically damaged yaw ring bolts (Photo by Joe Smith, 

NREL PIX# 22249)..............................................................................................................26

Figure 18 Strain relief prevents the cable twist from transferring to the cable decouples at the 

tower base (Photo by Joe Smith, NREL PIX# 22240).........................................................27
Page 6 of 42

1. Background

This test was conducted as part of the U.S. Department of Energy’s (DOE) Independent Testing 

project. This project was established to help reduce the barriers to wind energy expansion by 

providing independent testing results for small turbines. Five turbines were tested at the 

National Wind Technology Center (NWTC) as part of round one of this project. Safety and 

function testing is one of up to five tests that may be performed on the turbines, including 

duration, power performance, noise, and power quality tests. Test results provide manufacturers 

with reports that can be used to fulfill part of the requirements for small wind turbine certification.

The test equipment includes an Entegrity Wind Systems EW50 wind turbine mounted on a 30.5-

m (100-ft) monopole tower manufactured for the EW50 by Maico Industries, Inc. The controller 

was manufactured by Orbital A/S. Concrete mat foundation was installed per Entegrity designs 

by a third party, under contract to National Renewable Energy Laboratory (NREL). The system 

was installed in March 2009 by the NWTC Site Operations group with guidance and assistance 

from several Entegrity personnel.

2. Test Objective

The objective of this test was to:

• Verify whether the test turbine displays the behavior predicted in the design

• Determine whether provisions relating to personnel safety are properly implemented

• Characterize the dynamic behavior of the wind turbine at rated and higher wind speeds.

NREL does not limit the safety and function test to features described in the wind turbine 

documentation. NREL also inspects—possibly tests—and reports on features that are required 

by IEC 61400-2 and that might not be described in the wind turbine documentation. NREL 

conducted this test in accordance with Section 9.6 of the IEC standard, “Wind Turbines—Part 2: 

Design Requirements for Small Wind Turbines,” IEC 61400-2, second edition, 2006-03.

3. Description of Test Turbine and Setup

The test turbine was an Entegrity EW50 wind turbine. The EW50 is a downwind, 3-blade, 

passive-yaw, horizontal-axis wind turbine, manufactured by Entegrity Wind Systems Inc. The 

blades are fixed pitch, and the turbine employs an asynchronous generator and operates at a 

fixed speed to deliver three-phase electric power at 60 Hz. Table 1 lists the configuration of the 

Entegrity EW50 that was tested at the NWTC. Figure 1 is a picture of the EW50 at the NWTC.
Page 7 of 42

Table 1 Test turbine configuration

Turbine manufacturer and address

Entegrity Wind Systems Inc

4855 Riverbend Rd.; Ste 100

Boulder, CO 80301

Model name EW50

Production date January 2009

Gearbox serial number 543132-007

Generator serial number C0812180024

Design nominal voltage at terminals 415-600 Vac

Maximum current at terminals 108 A

Design frequency at terminals 60 Hz

SWT class II

Design 50-year extreme wind speed, Ve50 59.5 m/s

Rotor Diameter 14.9 m

Hub Height (vertical center of rotor) 31.1 m

Tower Type 30.5-m (100-ft) freestanding monopole

Rated Electrical Power 50 kW

Rated Wind Speed (lowest wind speed at which 

turbine produces rated power) 11.3 m/s

Rated rotor speed (lowest rotor speed at which 

turbine produces rated power) 65 rpm

Rotor speed range 64-70 rpm

Fixed or variable pitch Fixed with tip brake

Number of Blades 3

Blade Tip Pitch Angle 5.14 ̊ to 5.17 ̊ at 75% span

Blade make, type, serial number Entegrity, epoxy/glass fiber, 7.2 m, 150 kg, 

s/n: 284, 285, 283

Description of control system (device and software 

version)

TMC microprocessor by Orbital A/S in Entegrity 

enclosure version: “EW15 2.031”

Measurements verified the rotor diameter and hub height. Rated power and rated wind speed 

listed in the table are as published by Entegrity.

The test turbine is located at site 1E.1 at the NWTC, which is approximately 8 km south of 

Boulder, Colorado. The terrain is mostly flat with short vegetation. The site has prevailing winds 

bearing approximately 290 degrees relative to true north.

Figure 2 shows the general electrical arrangement. The wire run from the controller at the base 

of the tower to the point of grid connection at the data shed is approximately 100 m. The 

connection is made using 1/0 American Wire Gauge (AWG) wire for the three hot lines and 

neutral line, with a #2 AWG wire for the ground wire. The data shed houses the power

instrumentation, disconnect switch, and data acquisition system. The transformer was located 

outside and adjacent to the data shed, which first stepped the voltage up to 480 V and then to 

13.2 kV for the NREL grid.
Page 8 of 42

Figure 1 Entegrity EW50 test turbine at the NWTC

(Photo by Joe Smith, NREL, PIX# 22243)
Page 9 of 42

Figure 2 Electrical single-line drawing of EW50 installation

4. Instrumentation

The following parameters were measured in this test: wind speed, wind direction, electrical 

power, rotor speed, and grid voltage. The rotor speed was measured using a proximity sensor 

on the turbine generator shaft (this signal is also a controller input). An indication of turbine 

status was obtained by measuring the voltage of the grid and turbine brake voltage in the 

controller. The instruments used for these measurements are listed in Table 2. The calibration 

sheets for the instruments used for this safety and function test are included in Appendix A.
Page 10 of 42

Table 2 Equipment used in the power performance test

Instrument Make and Model Serial Number Calibration Due Date

Power transducer Ohio Semitronics, DMT 1040E 07070473 12 Feb 10

9 Feb 11

Current transformers Ohio Semitronics, 12974

001293045

001235428

001293049

Calibrated with power 

transducer

Primary anemometer Thies, First Class 0707884

0609010

25 Feb 10

22 July 11

Reference 

anemometer NRG, Max 40 179500049025 n/a

Wind vane Met One, 020C with Aluminum Vane U1477

W1474

25 Feb 10

24 Feb 11

Rotor speed

from controller

Weidmuller WOS 1 (p/n 827539)

Optocoupler

n/a n/a

Turbine status; brake 

status

from controller

Weidmuller WOS 1 (p/n 827539)

Optocoupler

n/a n/a

Data acquisition 

system

Compact DAQ w/LabView 

cDAQ backplane (9172)

NI 9229

NI 9205

NI 9229

NI 9205

12E4CEB

13DEC38

13E3D05

12CBC7A

12ECB77

n/a

10 Nov 09

12 Nov 09

18 Jan 11

18 Jan 11

5. Procedure

Safety and function testing can involve some risk to personnel and to equipment. By incorporating appropriate controls into testing procedures, NREL endeavors to accomplish its tasks with 

minimal risk. This test report documents these controls in areas where they might have 

influenced the results obtained.

5.1. Control and Protection System Functions

In the list below, turbine response was observed for each major response category (startup, 

normal shutdown, emergency shutdown). If faults or other actions cause one of these major 

responses, NREL simulates the appropriate faulting action and verifies that the control and 

protection system appropriately sensed the condition, and provide an indication of an 

appropriate response. This procedure enables, for example, all the E-stop functions to be 

checked without exposing the turbine to multiple, potentially damaging stops. These checks are 

designated by the term “behavior” in the list below.

1. Power control

2. Rotor speed control

3. Yaw orientation
Page 11 of 42

4. Startup

a. Normal operation – winds rising above cut-in

b. After maintenance or fault clearance at design wind speed or greater

c. Maintenance of fault conditions at design wind speed or greater

5. Normal shutdown

6. Emergency shutdown during operation

7. Behavior upon excessive vibration

8. Behavior upon loss of load

9. Turbine specific checks

5.2. Personnel Safety Provisions

The second part of the test procedure is to evaluate provisions for personnel safety. For this 

turbine, the following list of NWTC-standardized safety and function issues were reviewed:

1. Safety instructions

2. Climbing 

3. Standing place, platforms, and floors

4. Electrical and grounding system

5. Fire resistance and control

6. Fire extinguisher

7. Emergency stop buttons

8. Lock-out / tag-out provisions

9. Interlock on electrical cabinets

10. Safety signs

11. Unauthorized changing of control settings

12. Lightning protection

13. Presence and functioning of rotor and yaw lock

5.3. Dynamic Behavior

NREL staff observed the turbine at all operating wind speeds to note the dynamic behavior of 

the turbine, including (but not limited to) vibration, yaw behavior, and noise.

6. Results

The results reported here are based on the test conducted from April 2009 through October

2010. The majority of controller settings were tested in October 2010.

6.1. Control and Protection System Functions

NREL limited testing to investigation of single-fault failures and has not investigated failures of 

“safe life” components, e.g., NREL did not investigate the tower, and considered it a “safe life” 

component. NREL does not make judgments on whether such failures are likely, or whether 

additional features in the control and protection system are needed to protect against such 

consequences.
Page 12 of 42

Power control

Figure 3 and Figure 4 show that the power output of the turbine system is limited. The power 

curve scatter plot is characteristic of a stall-regulated wind turbine, as expected. There are large 

negative power events shown in Figure 3, which occur as the turbine is motoring up to an 

aerodynamically efficient speed in winds around cut-in. This behavior is programmed into the 

controller.

Rotor speed control

The EW50 is a constant-rotational-speed turbine when it is generating (see Figure 5).

Figure 8 shows the rotor speed versus wind speed. Some hysteresis can be seen in wind 

speeds between 3 and 7 m/s, which is around cut-in. The scatter data reveal a second 

horizontal grouping at 63 rpm between 8 and 15 m/s; this value is lower than the main line, 

which has a slight positive slope. This secondary line occurs when the EW50 is operating in an 

upwind orientation.

The tip brakes are held in place with an electromagnet. The magnet holds the brake in place as 

the rotor is spinning. In the event of an over speed, the brakes would deploy centripetally, and 

slow the rotor speed before the parking brake is deployed. In the case of a grid failure, the 

electromagnet loses its magnetism and the brakes deploy, slowing the rotor speed before the 

parking brake is deployed. After the tip brakes are deployed and the parking brake stops the 

rotor, springs retract the tip brakes and return them to their pre-deployment position.

Yaw orientation

The EW50 is a downwind, passive yaw turbine. NREL observed yaw behavior frequently during 

the test period and compared yaw position with the nearby wind vane’s indication of wind 

direction. Yaw error could be significant. Winds of greater than 6 m/s were needed to yaw the 

turbine into a downwind position, while the controller is programmed for a cut-in at 4.5 m/s. If the 

winds were perpendicular to the rotor, the winds might need to be even higher to yaw the 

turbine to the downwind position.

During operation, the turbine would yaw around the average wind direction. During some yaw 

events, the rotor was observed to yaw approximately 60 degrees in one second. In gusty winds,

the turbine on many occasions turned upwind in lulls, and was trapped in the upwind position 

when the wind speed increased. This upwind operation can be seen in the secondary curve in 

Figure 4 and Figure 7. In Figure 4 this secondary curve is most clearly visible by the maximum 

values (red) which are around 7 kW between 7 and 10 m/s. The average values (blue) are 

partially obscured in this plot, so in Figure 7 only the average power production values are 

plotted against wind speed for upwind operation. It is notable that in upwind operation, the 

power peaks between 8 and 10 m/s, above which it tends to go negative.

Spring weather at the NWTC is usually gusty, and an analysis during several months of springtime operation was performed. Results showed the EW50 operating in the upwind orientation 

about 3% of the time. This resulted in an approximate 5% loss of energy because the turbine 

consumed power during dips in gusty wind conditions in order to maintain operational rotor 

speed, thus lowering its power production curve.
Page 13 of 42

The droop cable can over twist. There are connectors intended to decouple the droop cables, in 

order to prevent them from over twisting. However, because of the strain relief installation, these 

connectors were isolated from the twisting, and they will not decouple before the cables over 

twist. See Figure 18, which shows that the cables above the strain relief are twisted, and the 

cables are untwisted below the strain relief; the decoupling connectors are below the strain 

relief. Once during the 18 months of operation the cable was untwisted by decoupling the

connectors and untwisting the cables. Figure 18 shows the level of cable twist after 

approximately one year at the NWTC. The Entegrity 6-month inspection record lists checking for 

cable twist.

Startup

The controller is programmed for a 4.5-m/s cut-in wind speed. The EW50 has an anemometer 

on the generator to measure the wind speed. When the 10-minute average wind speed was 

above cut-in, the brake on the high-speed shaft (parking brake) would release, the tip-brakes 

would be energized (holding them in operating position), and the rotor could freewheel. When 

the rotor reaches a speed of 64 rpm (1800 for the generator) the generator connects to the grid.

With the generator connected to the grid, the rotor spins between 62 to 65 rpm.

The EW50 also has a motor-up function. If the winds are above programmed cut-in speed

(4.5 m/s) and the rotor does not reach 64 rpm, the generator connects to the grid and behaves 

as a motor in order to spin the rotor. Because the NWTC’s air density is approximately 80% of 

sea level, the wind speed needs to be above 5.5 m/s for the EW50 to freewheel up to 64 rpm.

The difference between the programmed cut-in and the necessary winds to operate the EW50 

resulted in many motor-up events during the test period. This sequence of events can be seen 

in Figure 6.

Figure 6 shows that winds were greater than 4.5 m/s and the controller released the brakes and 

freewheeled for 10 minutes. However, the winds were not high enough for the rotor to reach an 

operational speed of 64 rpm. The generator motored-up the rotor, consuming just over 130 kW 

for approximately one second, and the rotor nearly reached operating speed. With the inertia of 

the spinning rotor, the rotor speed was maintained for about six minutes. After six minutes, the 

winds were strong enough to increase the rotor speed to operational speed and the generator 

connected to the grid. When the contactors connected the generator to the grid, the rotor speed 

was fixed between 62 and 65 rpm. When the gust that accelerated the rotor passed, the

generator began consuming power to keep the rotor at operational speed. This can be seen by 

the slightly negative power output in the last minute of Figure 6.

Normal shutdown

If the EW50 consumes power for 10 minutes, the controller will deploy the tip brakes. The tip 

brakes slow the rotor to approximately 18 rpm, which is 500 rpm for the generator. The parking 

brake is then deployed, which quickly brings the turbine to a stop. If the tip brakes cannot slow 

the turbine in 30 seconds, the parking brake is deployed. This 30-second delay between tip 

brakes and parking brake can be seen in Figure 12.

This turbine has a cut-out wind speed. It will deploy its brakes if the 10-minute average wind 

speed is 25 m/s or more.
Page 14 of 42

Emergency shutdown during operation from any operating condition

Turning the rotary switch on the controller panel to “stop” will first decrease the rotor speed, by 

deploying the tip brakes. Then the parking brake is deployed when the rotor slows to 

approximately 18 rpm (generator is at 500 rpm) or 30 seconds has elapsed since tip 

deployment. The parking brake is applied to the high-speed shaft, and it quickly brings the 

turbine to a stop. Figure 9 and Figure 12 show stops commanded by the rotary switch on the 

controller panel. Figure 12 shows that the parking brake was deployed after 30 seconds. This 

type of stop is identical to normal shutdown.

Behavior upon excessive vibration

The turbine has no means to sense excessive vibration or to shut down should excessive 

vibration occur. The IEC turbine design standards require such sensors on large turbines but 

not on turbines smaller than 200 m2

.

Behavior upon loss of load

In the event of a grid outage, the EW50 will come to a stop in the manner described above in 

“Emergency shutdown during operation from any operating condition,” and as shown in Figure 9

and Figure 12.

During the test at NREL, the controller’s universal power supply (UPS) failed and was put into 

bypass mode. In normal operation, the parking brake’s solenoid is energized through the 

controller’s UPS, and the brake pads are held off of the brake disk. Without the UPS, the

parking brake deploys at the same time as the tip brakes, and the rotor comes to a sudden stop.

This event is shown in Figure 10.

Turbine-specific checks

The EW50 controller has several set points. Some of these were tested by changing the set 

points and witnessing the turbine behavior.

One test was on the setting for generator over speed. The normal generator over speed 

condition is set at 1890 rpm. The test event involved changing the generator’s over speed limit 

to a level near operating condition, specifically 1801 rpm. The turbine started as normal, and 

when the generator speed reached the new over speed set point, it stopped by deploying 

brakes. The controller recorded the error type and time. Figure 12 shows this event. The EW50 

operated as designed.

Other tests that included changed controller set points were:

• Test generator over power: Power output greater than 45 kW for 10 s, from the standard 

set point of 75 kW for 300 s

• Test rotor speed: Rotor speed greater than 64 rpm, from 70 rpm

• Test grid balance: Current difference between lines greater than 5 A, from 30 A

• Test low grid frequency: Grid Frequency less than 60.2 Hz, from 59 Hz

• Test high grid frequency: Grid Frequency greater than 60.2 Hz, from 61 Hz

For each of these tests the EW50 operated as designed.
Page 15 of 42

6.2. Personnel Safety Provisions

Safety instructions

NREL received a 2008 edition of the “EW50 wind turbine user manual.” The manual provided a 

guide to operating the controller (manufactured by Orbital A/S), turbine limit settings and wiring 

diagrams. Some of the Orbital wind turbine controller settings did not apply to the EW50, such 

as the yaw functions. The manual did not provide any safety instructions to the owner. While the 

Orbital wind turbine controller was extensively covered, there was no mention of the rotary stop 

switch on the controller’s front panel, the yaw lock cable inside the tower, nor safe operating 

instructions. Some of the drawings referenced previous models of the EW50 design.

Entegrity does not provide an installation manual to the owner because the company’s 

personnel install all the turbines. Foundation specifications were provided by Entegrity and 

NREL contracted a third party to install the foundations.

There are 6-month and 1-year maintenance checklists, and these services were scheduled to 

be performed by Entegrity personnel.

NREL checked the manual to determine if the safety instructions addressed requirements in the 

IEC small turbine design standard and found the following issues:

• There are no instructions to disengage the load and/or energy sources

• There are no instructions to stop and secure the rotor. Although the Orbital controller has 

a “stop” command, it is not described beyond “stop turbine”.

• There are no instructions to stop and secure the yaw mechanism. Although there is a 

yaw lock mechanism to secure the yaw, it was not documented.

Climbing

The monopole tower comes with an external ladder and safety cable to access the turbine.

However, these were not installed on the turbine NREL tested, and therefore no comments can 

be made on ladder safety provisions.

There is an internal ladder to access the auxiliary controller cabinets. This ladder does not allow 

the climber to get much more than 3 m above the turbine foundation.

Standing places, platforms, and floors

There is a small, very narrow platform near the top of the tower. A person could stand on it, but 

would have to be tied off to the nacelle to prevent falling off. There is no railing or hand hold for 

this platform. There is no ladder to this platform, so the user must access this platform for an 

aerial lift or similar method.

Electrical and grounding system

The user manual includes single-line drawings of the electrical system and pin-outs for the 

controller. The installation checklist includes the line “Electrical system grounded to electrical 

code requirements.” The heavy gauge wire (1/0 AWG) had to be routed through the panel 

differently than Entegrity’s usual installations in order to meet code. The tower was also 
Page 16 of 42

grounded, but this inspection task is not listed in the installation checklist that was provided to 

NREL. The single-line drawings show that the tower is grounded.

Fire resistance and control

The controller has a generator temperature circuit breaker and a lightning suppressor. These 

components are connected to the controller, and when activated they will shut down the turbine 

and provide an error code that can be accessed through the control panel. There is a 

temperature sensor in the control cabinet, but it controls a heater, which is activated when the 

temperature is less than -5 ̊C. A high-temperature reading from the cabinet temperature sensor 

does not lead to turbine shutdown or produce fault codes.

Fire extinguisher

NREL provided a fire extinguisher in the building that housed the inverters. The manufacturer 

does not provide fire extinguishers or recommend that they be installed.

Emergency stop button 

The turbine has a stop button on the front of the control panel, which is shown in Figure 13.

However, if grid power is lost while the rotary switch is set to “stop”, and controller power is 

restored, the turbine will act as if it is in “run.” Turning the switch to “control power off” prevents 

this type of unintentional run.

Lock-out / tag-out provisions

The EW50 manual does not identify a means to re-energize and secure the turbine. NREL 

wrote its own procedure and followed it when performing up-tower and electrical inspections on 

the EW50.

Interlock on electrical cabinets

There are no interlocks on the controller enclosure.

Safety signs

1. There is a warning to “Disconnect power supply before servicing” on the lower right 

corner of the EW50 controller enclosure, see Figure 16.

2. NREL added labels indicating the voltage levels on all enclosures, electrical panels, and 

disconnects, as well as a notice for authorized use only, see Figure 14, Figure 15, and 

Figure 16.

Unauthorized changing of control settings

The controller settings can be changed by any user familiar with the menu system; there is no 

password protection on the controller. The controller is inside the tower, and the tower door has 

hasps that could be locked. When personnel were not accessing the controller, this door was 

always locked at the NWTC.

Entegrity personnel could access the controller though a remote log-on. They could change the 

control settings; however, it was requested that they not change the settings while the turbine 

was being tested at the NWTC. The settings were checked several times throughout the test to 

verify the setting remained the same as when the test started.
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Lighting protection

The turbine has a lightning suppressor module in the control panel, and if a high-voltagepotential event occurs, the module is designed to protect the rest of the turbine and generate an 

error code, which can be accessed through the controller. The tower was grounded as a 

precaution against lightning.

During the test period, no direct or nearby lightning strikes were observed. 

Presence of rotor and yaw lock

The EW50 was delivered with a yaw lock mechanism, in the form of a spring loaded pin, which 

inserts between bolts on the yaw ring. However the wire clamps holding the pin appear to have 

loosened (or never were tight enough) and the pin slowly moved into position. During this slow 

failure the yawing motion of the turbine bent the pin over into an inoperable position and 

scraped most of the bolts in the yaw ring; see Figure 17.

Documentation

Most of the EW50 manuals that were provided to NREL were in draft form. Some of the 

documentation was confusing, with references to EW50, EW15, and AOC 15/50 turbine models.

Many of the manuals were for Entegrity’s internal use because Entegrity personnel install and 

maintain the fleet of EW50 turbines. In these Entegrity internal documents there were 

inaccuracies, such the weights of the base section of the monopole tower and the 

generator/gearbox assembly. What is provided to a prospective owner in the “EW50 Wind 

Turbine User Manual” (2008 edition) is insufficient for the safe operation of the EW50. However,

the owner is not expected to interact with the turbine in a technical manner. This manual comes 

with the controller, and is located in a pocket inside the control panel door.

NREL checked the manuals and documentation to determine if the turbine met the 

documentation requirements in the IEC small turbine design standard and noted many issues.

The following information was lacking in the documentation provided to NREL:

• How to properly use the front panel rotary switch

• How to secure the yaw mechanism

• Howe to de-energize the system

• How to safely climb the tower

• What to do in case of a non-auto restarting error.

6.3. Dynamic Behavior

The operation was observed by NREL personnel for at least 5 minutes at wind speeds of 

approximately 5 m/s, 10 m/s, 15 m/s, and 20 m/s for a total observation period of at least 1 hour. 

NREL did not measure accelerations on the EW50.

The EW50 produced a significant amount of gearbox noise. When the generator was operating 

at synchronous speed, the turbine was relatively quiet, but it was not quiet when the generator 

was operating at sub-synchronous or super-synchronous speed. Significant amount of noise

was produced when the brakes were deployed. The parking brake deployment slams the tip 

brakes back to their stow/operate position and cause a shudder through the entire turbine.
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Although vibrations could be felt in the tower and sometimes seen, the vibrations were not 

deemed excessive.

Yaw oscillations could be severe at times, particularly in gusty winds. The rotor was seen to 

swing 60 degrees in approximately one second. In gusty winds, the rotor could get stuck 

upwind, a position, which, in winds below approximately 10 m/s, appeared almost as 

dynamically stable as the downwind orientation. In winds above 15 m/s the turbine rarely 

operated in the upwind position.

6.4. Graphs and Plots of Turbine Responses

Figure 3 Power response to wind speed, 1-minute data 

(Red–maxima, Green–minima, Blue–average, Black–bin average)
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Figure 4 Resized power axis of Figure 3. 

(Red–maxima, Green–minima, Blue–average, Black–bin average)

Figure 5 Normal operation in winds around rated wind speed, 1-Hz data
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Figure 6 Motor-up in winds around cut-in; 1-Hz data, showing 20 minutes

Figure 7 Upwind Power and Cp curves; 10-second data
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Figure 8 Rotor speed as a function of wind speed, bin averages in black; 1-minute data

Figure 9 Control panel rotary switch to “Stop” winds above rated; 1-Hz data
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Figure 10 Grid disconnect; without controller UPS, brakes act immediately; 1-Hz data

Figure 11 Restart in winds greater than rated; generator over-speed detected (altered set 

points); 1-Hz data
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Figure 12 Commanded “Stop” in gusty winds; tip brakes deployed for 30 seconds, then 

parking brake engages to stop rotor; 1-Hz data

Figure 13 Control panel, showing a rotary switch

(Photo by Joe Smith, NREL PIX# 22247)
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Figure 14 Signs on outer enclosure of control panel; “Notice” sticker added by NREL

(Photo by Joe Smith, NREL PIX# 22244)
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Figure 15 EW50 lockable disconnect switch at data shed

(Photo by Joe Smith, NREL PIX# 22242)

Figure 16 Warning sign on outer cover of EW50 control panel

(Photo by Joe Smith, NREL PIX# 22245)
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Figure 17 Bent yaw lock pin and cosmetically damaged yaw ring bolts

(Photo by Joe Smith, NREL PIX# 22249)
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Figure 18 Strain relief prevents the cable twist from transferring to the cable decouples at 

the tower base (Photo by Joe Smith, NREL PIX# 22240)

7. Exceptions

7.1. Exceptions to the Standard

None.

7.2. Exceptions to NWTC Quality Assurance System

The DAS modules were used beyond the calibration due dates. These were calibrated post-test 

and were found to have held their calibrations for the test period. Appendix A includes the posttest calibration sheets.
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8. Reference Document List

“EW50 Wind Turbine User Manual” (2008 edition)

“EW50 Orbital controller standard limit settings” (27 March 2009)

“EW50 Commissioning Documents”

“EW50/EW15 1 year advanced inspection record”

“EW50/EW15 6 month inspection record”
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A. Appendix - Equipment Calibration Sheets

A.1. Primary anemometer calibration sheet; 1st instrument; installed 25 February 

2009, removed 24 February 2010

A.2. Primary anemometer pre-test calibration; 2nd instrument; installed 24 February 

2010, removed 23 July 2010

A.3. Primary anemometer pre-test calibration; 3rd instrument; installed 23 July 2010, 

used until end of test

A.4. Power transducer calibration sheet; installed 25 February 2009, removed 8

February 2010

A.5. Power transducer calibration sheet; recalibrated and reinstalled on 19 February 

2010, used until end of test

A.6. Wind vane calibration sheet; 1st instrument; installed 25 February 2009, removed 

24 February 2010

A.7. Wind vane calibration sheet; 2nd instrument; installed 24 February 2010, used 

until end of test

A.8. NI 9229 data acquisition module calibration; 1st module; installed 25 February 

2009, removed 3 Feb 2010 (calibration pasted due)

A.9. NI 9205 data acquisition module calibration; 1st module; installed 25 February 

2009, removed 3 February 2010 (calibration pasted due)

A.10. NI 9229 data acquisition module post-test calibration; 1st module

A.11. NI 9205 data acquisition module post-test calibration; 1st module

A.12. NI 9229 data acquisition module calibration; 2nd module; installed 3 February 

2010, used until end of test 

A.13. NI 9205 data acquisition module calibration; 2nd instrument; installed 3 February 

2010, used until end of test
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Figure A.1. Primary anemometer calibration sheet; 1st instrument; installed 25Feb09, 

removed 24Feb10
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Figure A.2. Primary anemometer pre-test calibration; 2nd instrument; installed 24Feb10, 

removed 23Jul10
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Figure A.3. Primary anemometer pre-test calibration; 3rd instrument; installed 23Jul10, 

used until end of test
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Figure A.4. Power transducer calibration sheet; installed 25Feb09, removed 8Feb10
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Figure A.5. Power transducer calibration sheet; recalibrated and reinstalled on 19Feb10, 

used until end of test
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Figure A.6. Wind vane calibration sheet; 1st instrument; installed 25Feb09, removed 

24Feb10
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Figure A.7. Wind vane calibration sheet; 2nd instrument; installed 24Feb10, used until 

end of test
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Figure A.8. NI 9229 data acquisition module calibration; 1st module; installed 25Feb09, 

removed 3Feb10 (calibration pasted due)
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Figure A.9. NI 9205 data acquisition module calibration; 1st module; installed 25Feb09, 

removed 3Feb10 (calibration pasted due)
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Figure A.10. NI 9229 data acquisition module post-test calibration; 1st module
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Figure A.11. NI 9205 data acquisition module post-test calibration; 1st module
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Figure A.12. NI 9229 data acquisition module calibration; 2nd module; installed 3Feb10, 

used until end of test
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Figure A.13. NI 9205 data acquisition module calibration; 2nd instrument; installed 

3Feb10, used until end of test