The toughest encoder for the most challenging conditions

Ideally suited to the wind power generation industry, the NorthStar Series HD35R Generator Encoder is designed with harsh conditions in mind. It features advanced optical ASIC technology and encapsulation technologies that ensure long-term resistance to dust, water, heat, mechanical shock, vibration and more. Features include phased array sensor for reliable signal output, rugged design with wide-spaced oversized bearings, unbreakable code disc (up to 5000 PPR), improved seal design for increased moisture resistance, extended temperature range of -40 to +100°C, IP67 Enclosure Rating.

DYNAPAR

www.dynapar.com

 

Hollow-shaft version of magnetic rotary encoder

The Magnetocode (MCD) absolute rotary encoders feature reliability, accuracy, and adaptability. Now, a new hollow-shaft version of the MCD encoder makes it easy to mount these devices on shafts up to 20-mm dia. The recent devices are available with analog (voltage/current) or digital electrical interfaces. Analog versions are a substitute for traditional potentiometers, offering superior reliability, longevity, and accuracy than units they replace. The measurement technology is based on a rotating magnet and Hall-effect sensors. Unlike traditional potentiometers, there is no contact between these components and no loss of accuracy due to wear or surface contamination. Another advantage is a flexible range-setting feature. With this, the installer can ‘teach’ the device the limits of mechanical motion that will be experienced during operations. Once these limits have been defined – which can involve multiple rotations – the device will self-calibrate so the full range of the electrical output (e.g. 0-5 volts) exactly matches the full range of mechanical movement. This improves the overall accuracy of the control system. Buttons and LEDs on the casing of the analog-output models simplify set-up. MCD encoders are well suited for applications requiring extended multi-turn capabilities (up to 8,192 revolutions). A self-powered rotation-counter (based on Wiegand wire technology) records the number of rotations – even if these occur when there is no power supplied to the sensor.

Digital outputs for MCD encoders include serial (SSI), CANopen and DeviceNet.

MCD encoders are tough. Heavy-duty enclosures protect the measurement components from mechanical loads, shock, and vibration, dust and moisture (up to IP 69K ratings). Hollow-shaft versions have a permanently lubricated steel and brass gear-set for a long, trouble-free service life.

FRABA Inc.
www.fraba.com

Rugged encoder line adds another for wind turbines

A line of rugged encoders has added a heavy duty, incremental, shafted version to deliver superior reliability in tough wind generator, steel, and paper applications. The HD35R, made by Dynapar in the U.S., will feature a 10-day lead time, and will be an excellent alternative to the Hubner POG90, according to the company.

A few features include a:

• 100-mm IEC flange with an 11-mm shaft containing a 4-mm key for European standard motor mounting.

• Dynapar’s phased array, wide-gap encoder engine, combined with a plastic code disk, to deliver superior shock and vibration resistance.

• Two, large-gauge, over-sized bearings to handle excessive shaft loading, up to 100-lb axial and 50-lbs radial.

• IP67 rated for work in harsh duty environments

• Sealed junction box for field wiring and protection against moisture.

• Wide temperature spec of -40 to 100°C for higher temperature applications.

Dynapar

http://www.dynapar.com/Products_and_Solutions/Series_HD35R_Heavy_Duty_Encoder/

Stainless steel encoders

Sensor products deployed in harsh environments demand specific housing and sealing techniques as protection against prevailing adverse conditions. Typical applications include the offshore industry, chemical industry, and container ship loading facilities. Encoders installed there must withstand salty air, aggressive media and lubricants, oils and cleaning agents. Baumer offers a wide range of stainless steel encoder designs that meet all these demanding requirements.

The Baumer encoder portfolio comprises incremental and absolute encoders that come in stainless steel housings and are intended for operation under extreme ambient conditions. The compact encoders are available with all common housings, as solid or hollow shaft designs and provide IP68 and 69K protection. For demanding applications in potentially explosive atmospheres there are ATEX-certified variants. Thanks to the interface versatility the encoders offer a high degree of flexibility for easy integration into automation systems. Users can choose between SSI, fieldbus and Ethernet interfaces such as CANopen, DeviceNet, EtherCAT, EtherNet/IP, SAEJ1939, Profibus, PROFINET or POWERLINK.

A highlight in the stainless steel encoder range is the absolute multiturn encoder series “MAGRES hermetic“ with hermetically encapsulated electronics and sensing. Impermeable to fluids, the encoders provide IP68 and IP69K protection. The absolute encoder GE404 with optical sensing comes in an extremely reliable V4-A stainless steel design compliant to class 1.4404 or 1.4435. Viton seals are ultra-resistant against chemicals and high temperature. Incremental signal tracks are available as an option for simultaneous detection of rotational speed and velocity. Lastly, the multiturn-encoder series GEMMH excels with the modular bus cover concept. A modular bus cover hosting the required fieldbus electronics docks onto the basic encoder model.

Baumer Ltd.
baumer.com

What are wind turbine encoders?

These devices indicate the angular position of a rotating shaft. They are described most often as incremental or absolute.

Incremental encoders: This version needs an input voltage, often between 5 and 30 Vdc. The design is similar to a rotary switch in that it is on or off, so the output is 0 or the input (supply) voltage. When supplying an encoder with 5 Vdc, that will be the high output voltage. Because the output is either 0 or the input voltage, the output is always a square wave.

These are further identified in terms of pulses per revolution (ppr). A common incremental resolution is 1,024 ppr. So for every complete rotation, the encoder produces 1,024 pulses. Another common resolution is 2,048 ppr, but incremental encoders come in many different resolutions, from 1 to 10,000 ppr. Most applications in a wind turbine will be 1,024. On the generator, however, expect 3,072 ppr. Each pulse is exactly the same. A controller would count the number of outputs to know a shaft’s position.

Absolute encoders: These are a bit different. Their output data is relative to their position. They output a unique digital word for each individual position. They also output in several different field-bus-communication protocols. Instead of using pulses-per-revolution to describe their resolution, they use bits. Rather than say an absolute encoder has a resolution of 1,024 ppr, it is described as 10 bits.

Here are a few windpower applications. A common one is inside the turbine hub on pitch control units. Encoders are either sandwiched between pitch motors and brakes or on the back ends of motors. Shafted encoders are picked for these applications as well as hollow-shaft devices. An important element to keep in mind when looking at encoders for these applications is the temperature spec. it’s not surprising that encoders sandwiched between motors and brakes get hot, so make sure the selected device can tolerate the heat. Specs up to 130°C are not unusual.

Not all encoders are built to tolerate heat, so when they get hot, several things can happen. For one, glued components can come apart and cause the device to fail. Also, signal quality can be affected by extreme heat causing the drive system to misunderstand the position reported by the encoder. Both of these failures can be avoided by understanding the encoder’s capabilities.

Another common wind-turbine application is on the back end of a generator. Encoders there are used to regulate speed and, in some cases, determine position. Like the feedback used on pitch systems, generator feedback applications are considered mission critical. if either of these feedback applications fails, the turbine cannot produce power. Also expect encoder problems on those with undersized bearing on a generator. Failed bearings are the number one cause of generator-encoder failures. Electrical and thermal isolation further enhances feedback reliability.

One OEM uses a pulse encoder on each rotor blade and one to track where the turbine is pointing. The main control system uses that position information to optimize generator speed relative to wind speed and direction. It is essential to use reliable components because wind turbines are sited in areas with large temperature fluctuations. In addition, many wind turbines are offshore, so their components must be reliable and durable, otherwise servicing and maintenance costs can spiral out of control.

Magnetic hollow-shaft encoders: These provide a third type. They are hermetically-sealed magnetic encoders, heavy-duty devices said to detect wear and maintenance issues. one line of these encoders can be mounted onto generator shafts up to 740-mm diameter, yet have only a 27-mm profile. These encoders provide 17-bit single- turn resolution, which provides accurate speed, rotation, and position data even at low turning speeds. With FpgA signal processing, the encoders are precise, generating maximum incremental square pulses of 524,288 periods/ rev and a maximum sine/cosine interpolation of 32,768 periods/rev. The units come with an ip68 stainless steel encoder wheel and an ip67-rated sensing head. The encoders have no moving parts, light source, or breakable components. The manufacturer also makes hermetically sealed magnetic encoders also ip69K-rated. Such encoders are protected from salt, dust, temperature extremes, moisture, and other contaminants. The
most recent encoders of this sort feature a monitoring system that notifies users in advance regarding wear and maintenance issues. A checking system in the encoder monitors all functions over the full speed range and sends an alarm when needed.

Shock tolerant heavy-duty encoder insulated to 2.5 kV

This edited  article come from encoder manufacturer Leine & Linde

It’s sometimes the small modules such as rotary encoders in production equipment that make it necessary to shutdown a plant for their replacement in case of faults. This results in enormous costs, often way out of proportion to their size. In the windpower industry, revenue loss from downtime can average $50,000/week, part replacement can vary from $20,000 to $300,000, and if a crane must be mobilized, expect a $250,000 charge.

Such charges can be avoided by using rotary encoders capable of self diagnosis that indicates internal problems so maintenance can be planned as early as possible.

Rotary encoders are key components of modern machinery and plant controls, so it makes sense to equip them with a diagnostic system that continuously monitors the internal functions of the rotary encoder and provide a basis for initiating maintenance measures in good time. Rotary encoders used in production plants are often subjected to high stresses from shock and vibrations as well as high temperatures. The following typical component specifications reflect these stresses: Vibration-resistance up to 100 m/s², shock resistance up to 1,000 m/s², axial load 100N and radial loads to 300N. Under these general conditions a positioning accuracy of 0.1 mm must still be ensured.

 

Why rotary encoders fail

It is no wonder that rotary encoders break down in spite of their apparent durability. Encoders can fail for several reasons. For instance:

• Worn-out ball bearings due to poor installation: The connection of the rotary encoder to the motor shaft is made either with a coupling (typical for shaft encoders) or by plugging onto the shaft (typical for hollow shaft encoders). A torque support keeps the encoder from spinning. If the specified tolerances are not complied with, imbalance results, which causes premature wear to the ball bearings. The result: the increment-disc wobbles. Individual areas lose contrast, which in turn looses several pulses. This means the rotary encoder still functions, but the entire drive unit becomes irregular as the frequency inverter attempts to compensate for these fluctuations.
• A “loose contact” produces an imbalanced drive unit which puts excess strain on soldered joints and (terminal) contacts. Hence, bad contacting causes sporadic faults.
• Dirt in the rotary encoder clinging to the increment disc: The encoder then detects two increment lines as one and produces one pulse too few. This can happen with equipment in dusty regions common for windpower equipment, and especially when the nacelle cover is opened. In such cases it is advisable to use encoder versions with external plug connections.

• Moisture in the connector or in the housing: Cables too thin let moisture penetrate into the rotary encoder through the cable gland and cause sporadic malfunctions. This is especially possible in offshore windpower applications.

• Overheating: Rotary encoders are often installed behind a fan so the exhaust air from the motor passes over the encoder. If a motor runs hot, as it could as bearing fails, the hot exhaust air from the motor can cause the failure of the rotary encoder.
  

  Software for the ADS provides users with an overview of the type of rotary encoder problem, the time of the fault and the condition and encoder data.

A fault with many installations is also the fact that monitoring the rotary encoder is only implemented in the frequency inverter. However, between the inverter and rotary encoder there are enough cables and terminals to cause problems. For example, a crushed cable can lead to a signal interruption, which is mistakenly interpreted as an encoder fault by the inverter. Then an O&M crew would swap out a component without fixing the problem. A lot of these problems can be avoided if the encoder could tell why it is malfunctioning.

One such encoder from the author’s company has a built in early warning system called Advanced Diagnostic System (ADS). This automatic self-diagnosis works like this:

 

The rotary encoder internally monitors the completeness of the pulses and the correct pulse sequence. Even a single counter difference from the programmed division is registered by the system and reported via a potential-free switching output. This can, for example, be evaluated and displayed by an overriding system control system. For this an additional wire is necessary. In parallel to the switching output, the fault is indicated by a flashing LED on the rear of the housing. In case of upgrading, this allows using ADS without additional wiring. Often, rotary encoders are installed in visible position, so a sporadic visual check by the user is sufficient. The flashing LED can be easily seen at a distance of 10 m.

As part of ADS, the manufacturer stores the time of the fault and the corresponding error code in the rotary encoder so users have the opportunity to read out and analyze the error code via an RS-232 interface (once the encoder has been removed). For statistical purposes, the number of operating hours, speed of rotation and current temperature are also measured in the encoder. The highest and lowest temperature is also stored. In addition, there is a differentiation between individually occurring errors and continuous problems.

Leine & Linde
Leinelinde.com

The Sweden-based encoder manufacturer distributes in the U.S. through HEIDENHAIN Corp., Schaumburg, Illinois.

Heidenhain
heidenhain.com

Absolute encoder well suited for electric motors

Recent absolute, inductive rotary encoder. Called the ECI 119, this encoder sets itself apart with a low profile (height of 19 mm, outside diameter 92 mm) and large through shaft (50, 38, or 30 mm), making it well suited for electric motors in many applications.

The Heidenhain ECI 119 is a single turn, absolute encoder offering 524,288 (19 bit) positions per revolution, and provides ±90 sec system accuracy. An advantage of the ECI 119 is its bearingless design. As a modular encoder, there is no need to worry about bearing wear or loading, and concerns of mechanical self heating of the encoder and shaft currents are eliminated. If all the mounting tolerances are met, the encoder requires virtually no maintenance outside of contamination protection.

The company’s two types of output are offered: purely serial data (EnDat21) or serial data with 1 Vpp incremental signals (EnDat 01). The SSI interface can also be implemented, but this requires a minimum value order. The EnDat feature lets users transfer incremental and absolute position data along with online diagnostics.

A recent version of Adjusting and Testing Software is available with the ECI 119. The software allows diagnostic checks of the encoder position signals. And the ExI Mounting Wizard allows checking the scanning gap and signal amplitude to assess mounting quality. This ensures reliable and repeatable field mounting.

Heidenhain Corp.
www.heidenhain.us

Encoder comes with self diagnostics

To avoid false diagnoses or costly downtime an early warning system called ADS (Advanced Diagnostic System) is built into Leine & Linde’s 800 Series of rotary encoders. These devices are often subjected to high mechanical stresses in the form of shock and vibrations as well as high temperatures. Encoders with ADS have detected worn-out ball bearings due to poor installation, dust contamination, moisture issues, and overheating. These self-diagnosis system works by internally monitoring the completeness of the rotary-encoder pulses and the correct pulse sequence. Even a single counter difference is registered and reported by the system. This error is relayed as a flashing LED on the rear of the encoder housing. The time of the fault and the corresponding error code are stored in the encoder so users can analyze the error code via an RS-32 interface once the encoder is removed. A report can also be displayed directly at the machine if additional wiring is added to an overriding system control.

Leine & Linde
www.leinelinde.com
www.heidenhain.com

Rugged IP69-rated inductive sensors handles the harsh outdoors

For outdoor applications exposed to harsh environments, Baumer has introduced the IWRR/IFRR Inductive Sensors for object detection and distance measurement up to 12 mm. These reliable IP67 and IP69-rated sensors are sealed against moisture and contaminants and easily withstand temperature ranges from -40 to +80ºC.

Available in digital and analog versions, IWRR and IFRR inductive sensors meet the manufacturer’s rigorous standard, guaranteeing the sensors’ impermeability for reliable operation in demanding environments that involve changing temperatures. The company says these low-maintenance sensors have an expected MTTF greater than 100 years.

Because the sensors resist long-term exposure to salt water, oils, and aggressive detergents, they are especially suited to the demands of on and off-shore wind turbines.

The compact sensors are available with IP69-rated V4A stainless steel housings for strenuous offshore environments or IP67-rated nickel-plated brass housings for onshore applications. Digital inductive sensors are mainly used to detect nacelle position and rotor speed. Measuring sensors are applied for brake monitoring and shaft deflection.

In addition to wind power, the IWRR and IFRR Inductive Sensors offer proven performance in a range of applications such as heavy vehicles including refuse collection and forestry machines, solar wafer manufacturing, the rail industry, and other rigorous applications exposed to challenging outdoor environments with high and low ambient temperatures.

Baumer Electric
baumerelectric.com/usa

Encoder manufacturer launches new website

Dynapar has launched its newly revamped website, Dynapar.com. Intended to enhance the overall customer experience, it helps users find what they need in minutes to resolve their motion feedback control challenges. The company instituted the new, online customization capabilities to deliver the same level of service as an in-person consultation, at the customer’s convenience. A few new online capabilities include:

• A Product Configurator for easy product search and customization. Once customized,customers can then receive an email quote, contact a distributor or purchase directly online. Configurator searches can be conducted based on product type and mounting option or duty classification.
• Brands include Dynapar, NorthStar, Hengstler, Harowe
• Industries served include wind power, aerospace & defense and more.
• Expanded Service and Support section to locate distributors, compare competitor products and streamline product returns.
• Product Quicklinks provide a comprehensive portfolio of Dynapar’s encoders and resolvers, complete with downloadable PDF data sheets.

Dynapar
www.dynapar.com