Motion Control Tips

Automation • Motion Control • Power Transmission

How do rotary voice coil actuators work?

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Most linear motion devices have a rotary equivalent, and voice coil actuators are no exception. While the versions depicted in most product images and videos are linear, rotary voice coil actuators fill a need for smooth, arc-shaped motion and torque production with fast response times. But unlike the design relationship between rotary and linear motors, developing a rotary voice coil actuator isn’t simply a matter of taking the linear version and rolling it into a cylinder. While their components are the same, the configurations of linear and rotary voice coil actuators are quite different.

Voice coil actuators work on the principle of the Lorentz force, which is the force generated when a current-carrying conductor is placed in a magnetic field. In the case of a voice coil actuator, the magnetic field is created by permanent magnets and the conductor is a coil of wire. When current is applied to the coil, a force is generated, and the magnitude of the force is proportional to the applied current. (All other variables in the force production, such as magnetic flux and length of wire, are fixed for a given voice coil design.)

F = k*B*L*I*N

F = force (N)

k = force constant

B = magnetic flux density (tesla)

L = length of wire (m)

I = current (amps)

N = number of conductors

The most common linear voice coil actuator design features a moving coil, although the actuator can be constructed so that either the coil or the magnet is the moving part. In the moving coil design, a stationary cylindrical permanent magnet produces a radial magnetic field. Housed inside the permanent magnet cylinder is a coil that is wrapped around a non-conducting structure, or holder. The permanent magnet is housed in a ferromagnetic cylinder that is open at one end and has a “core” through its middle, which is necessary for completing the magnetic circuit. The coil assembly rides in the air gap between this core and the interior surfaces of the permanent magnet. Although it sounds complicated, the construction is actually quite simple, as shown below.

rotary voice coil actuator

The construction of a linear voice coil actuator is relatively simple. In this example, the magnet is stationary and the coil moves.

A rotary voice coil actuator is sometimes referred to as a “flattened” version of the linear design described above. In other words, to transform a linear voice coil actuator into a rotary version, place the linear voice coil actuator lengthwise on a table (as it would sit if it were operating horizontally) and flatten it into an essentially 2-D object. Then bend the ends so that it forms an arc (like a piece of macaroni). Now you have a rotary voice coil actuator.

rotary voice coil actuators

In this rotary voice coil actuator, the permanent magnet segments are on the top and bottom (white) and the coil (gold) rides in the air gap between them.
Image credit: BEI Kimco

Rotary versions provide torque rather than force. Similar to their linear counterparts, the amount of torque generated is proportional to the applied current, and the direction of the current determines the direction of motion. Excursion angles are typically less than 180 degrees, and commonly fall between 15 and 60 degrees.

Voice coil actuators are, technically, non-commutated DC motors. The term “voice coil” is often used because one of their first applications was to vibrate the paper cones in loudspeakers. Rotary voice coil actuators are also referred to as “arc segment” actuators or “limited angle torque motors” because they produce arc-shaped motion.

One of the strengths of voice coil actuators is their extremely smooth, cog-free motion with no torque ripple. This makes rotary versions ideal for applications that require high torque and quick response, such as gimbal positioners. They are also well-suited for moving optics and for controlling stabilization devices.

rotary voice coil actuators

This gimbal assembly design uses two rotary voice coil actuators. The inner axis moves 40 degrees in 32 milliseconds, and the outer axis moves 20 degrees in 140 milliseconds.
Image credit: BEI Kimco

Feature image credit: H2W Technologies, Inc.

New Unitronics VFD offerings for motion control — integrate with PLC + HMI products

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In keeping with a commitment to centralize and streamline industrial automation and control, Unitronics is announcing a new VFD line. Unitronics, the leading experts in the development and manufacture of integrated PLC + HMI controllers, has launched its own line of variable frequency drives (VFDs). With this launch, the manufacturer can better meet customer demand for motor and motion control solutions.

Inverters — also called variable frequency drives (VFDs) — optimize machine performance, save energy, and lower machine lifecycle costs across a range of applications, including packaging, conveyance and material handling, machining, pump and fan applications, and more.

Unitronics’ VFDs seamlessly integrate with their existing lines of PLC + HMI All-in-One controllers: UniStream, Vision, and Samba.

The addition of a VFD product line simplifies workflow by enabling customers to obtain VFDs, PLCs, and HMIs from a single supplier, program them all in a single software, and receive support from the same team throughout a project.

Unitronics VFDs offer options for both single and three phase VFDs from 0.4 kW and up to 110 kW. Features include:

EMC Built-In Filters  Braking units are built in to VFD
Mounting options: Wall, Flange, Rail Sensorless vector and torque control
Operates over wide temperature range STO (Safe Torque Off)
Modbus RTU fieldbus Heavy-duty overload capacity

The VFDs are also UL approved and TÜV SÜD Safety and CE Certified.

VFD configuration and operation

Pairing Unitronics VFDs with Unitronics controllers offers a faster, easier alternative to other VFDs on the market: all tasks can be programmed using the same software environment as the PLC and HMI applications. Unitronics’ software enables the user to rapidly set up, configure, and commission multiple VFDs, as well as to monitor and debug the VFD via online watch or Scope Trace graph.

Users can also operate their VFD directly from the controller’s integrated HMI panel, allowing them to take advantage of the full color touchscreen. Another major benefit of an All-in-One Unitronics solution is Remote Access; users can monitor the VFD via the software, web server, or even a VNC connection.

This addition from Unitronics allows OEMs to simplify and centralize their control needs, relying on fewer components from fewer vendors; they now can save time, budget, and effort with this all-in-one approach. Unitronics continues to uphold its commitment to innovating and integrating industrial automation.

Unitronics designs, manufactures, and markets quality PLCs for the global market. Easy-to-use, efficient, and affordable, the products have been automating processes, systems, and stand-alone applications since 1989. The manufacturer maintains more than 160 distributors in over 55 countries around the globe, enabling the customers to purchase the products with local marketing support.

Unitronics’ field-proven PLCs automate hundreds of thousands of installations in diverse fields — including petrochemical, automotive, food processing, plastic & textile, energy & environment, water & waste water management … anywhere automated processes are required. Unitronics’ programmable controllers have been honored by Frost & Sullivan’s 2016 Product Line Strategy Leadership Award, and have received numerous trade awards.

For more information, visit  www.unitronics.com.

What is the Department of Energy’s Integral Horsepower Rule?

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The U.S. Department of Energy (DOE) has been regulating energy efficiency for electric motors since 1997, when the Energy Policy Act went into effect, requiring most 1 to 200 hp general-purpose motors to meet NEMA Energy Efficiency standards. Since then, the DOE energy efficiency regulations have evolved, with the Energy Independence and Security Act (EISA) of 2007 upping the efficiency requirements for 1-200 hp general-purpose motors to the new NEMA Premium Efficiency levels and adding the requirement for certain 201 to 500 hp motors to meet NEMA Energy Efficiency standards.

integral horsepower rule

Image credit: ABB

However, the 2007 EISA standard — which went into effect in December of 2010 — left significant gaps in the motors that were covered and made it relatively easy for manufacturers to work around the rules by producing motors with slight deviations from those covered by the standard — such as special mounting designs not specified in the regulations.

In 2010, a motor coalition was formed in order to, “Determine and document a plan to improve the efficiency of the greatest number of units, providing the greatest savings impact while reducing potential enforcement issues, while maintaining full product utility for American industry.” As a result of this coalition’s work, the Amended Integral HP Rule was released in May of 2014 and was implemented in June of 2016 as the Integral HP Motor Final Rule.

This Integral Horsepower Rule supersedes the EISA standard and specifies that nearly all motors covered must meet NEMA Premium Efficiency levels. But more importantly, it closes the gaps and potential loopholes in the EISA standard and expands the scope of covered motors to those that meet the following criteria:

  1. Is a single speed induction motor
  2. Is rated for continuous duty (MG 1) operation or for duty type S1 (IEC)
  3. Contains a squirrel-cage (MG 1) or cage (IEC) rotor
  4. Operates on polyphase alternating current (AC) 60-hertz sinusoidal line power
  5. Has 2-, 4-, 6-, or 8-pole configuration
  6. Is rated 600 volts or less
  7. Has a three or four digit NEMA frame size (or IEC metric equivalent), including those designs between two consecutive NEMA frame sizes (or IEC metric equivalent) or an enclosed 56 NEMA frame size (or IEC metric equivalent)
  8. Has no more than 500 horsepower, but greater than or equal to 1 horsepower (or kilowatt equivalent)
  9. Meets all the performance requirements of a NEMA design A, B or C electric motor or an IEC design N or H electric motor
integral horsepower rule

Annual energy and cost savings that can be achieved by replacing a standard efficiency motor with a premium efficiency motor, versus repairing the standard efficiency version, as outlined in the DOE’s Integral Horsepower Rule.
Image credit: U.S. Department of Energy

Still, the Integral Horsepower Rule does not include all motors used in industrial applications. The most significant omissions from the rule, relevant to industrial motion and motion control include:

  • Synchronous AC motors
  • Permanent magnet rotor AC motors
  • Servo motors

But there’s a good reason these motors aren’t covered by the Integral Horsepower Rule. The DOE considers permanent magnet (PM) motors, switched reluctance (SR) motors, and synchronous reluctance (SynRM) motors to be “newly emerging” or “advanced” technologies that can achieve significantly higher efficiency levels than NEMA Premium Efficiency. In fact, these motors may meet or exceed “super efficiency” standards, which have been explored, but not finalized or published, by NEMA.

Specifically, NEMA recognizes that permanent magnet and switched-reluctance motors have both high power density (torque-to-weight ratio) and high efficiency and recommends that they be considered for many types of industrial applications, including:

  • When the application requires speed control (i.e., when an adjustable speed drive is required for speed regulation)
  • When driven equipment is in operation for over 2,000 hours per year
  • When an old standard efficiency motor is driving a centrifugal load with throttled or damper flow control and can be replaced with a variable speed PM or SR motor and controller
  • When operations involve frequent starts and stops (this is a good application due to the low inertia of PM and SR motors)
  • When small motors operate at partial load a good deal of the time
  • When the PM or SR motor can be used in a direct drive configuration to displace a single or two-speed motor with gearbox (e.g., a cooling tower fan drive motor), a gear motor, or a belted power transmission system
  • In vertical pump-mount applications where resonance frequencies must be avoided.

The chart below demonstrates the efficiency of permanent magnet motors as compared to NEMA Energy Efficient and Premium Efficiency motors, as well as to IEEE 841 motors.

integral horsepower rule

Full-load efficiency values for Permanent Magnet versus NEMA Premium Efficiency, IEEE 841, and NEMA Energy Efficient motors.
Image credit: Baldor Electric

NEMA Premium Efficiency sets forth full-load efficiency standards for 1 to 500 hp, three-phase, low-voltage NEMA Design A and B general, special, and definite purpose induction motors. Because the Premium Efficiency levels are provided in Table 12-12 of the NEMA MG1 Motors and Generators standard, it is sometimes referred to as “12-12 efficiency.” For motors not produced in the United States, the IE3 classification, as defined in the IEC 60034-30-1 standard, is generally compatible with the NEMA Premium Efficiency standard.

How to kill your favorite variable frequency drive

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Though not a complete list, following are some tried-and-true methods some have unintentionally used to destroy variable frequency drives (VFDs). Avoid the following situations to help your VFD live a long and fruitful life.

By Paul Avery | Product Training Engineer at Yaskawa America • Drives and Motion Division

You once loved your VFD. Shiny and new, it earned rebates from the local power-supply company so happy to see your facility becoming more efficient (by consuming less power during lightly-loaded conditions). The VFD also earned accolades for driving its connected motor in a way that was electrically and mechanically gentler than alternatives. Plus with its Ethernet option board, it tied into your facility’s ever-expanding network of devices.

But now, the VFD’s reliability has worked against you, and your coworkers think that it will never break down — and that they don’t need you anymore. So now you must kill that once-loved VFD before there are more of them. Just trip on a fault would be insufficient because you need it to die. But how?

This VFD died after conductive washers dropped into the top of the drive and short circuited the dc bus.

Bad power input into the VFD

A VFD will accept any power sent its way. Enough voltage of short duration (in the form of a voltage spike) exceeding the rating of the bus capacitors will:

  • Stress the VFD’s capacitors to beyond their breaking point and
  • Destroy the VFD’s metal-oxide varistors (MOVs) and diode bridges.

Sometimes even lesser amounts of voltage — those that are below the peak value the capacitors can withstand, but present over longer periods of time — can kill a drive. That’s especially true if there’s no way for the VFD to disconnect itself from the high incoming line. So in the case of spikes, avoid the use of line reactors or instantaneous overload devices if you truly want to end the VFD’s tyranny.

Under-sizing or overloading the VFD for the application

Wherever a VFD is undersized for the load that it will regularly experience, that drive (with its overload-protection function) will most likely trigger frequent trips. So great — how do we kill the VFD if it’s protecting itself?

Well, overload protection is there to protect the drive components from enduring too much current for too long a time. Key parameters here are current and time because in certain combinations, they may not trip instantaneous overload devices such as fuses. Even so, current over time can contribute to thermal issues that drastically shorten a VFD’s life. Excessive heating-to-cooling cycles occur as the drive trips, is reset, and then trips again. This thermal cycling induces the premature demise of critical VFD devices such as IGBTs.

Poor cooling of the VFD

Speaking of cooling, nothing kills drives like too much heat. Some drives will shut down if any of the cooling fans fail. What’s more, nearly every major VFD product has some kind of heatsink temperature monitoring. If the drive gets too hot because the heatsink is caked in oil and dirt, the drive will shut down before the devices attached to the heatsink reach thermal breakdown. So to ensure a premature demise for a VFD, simply run the drive until it overheats and trips, and then let it cool down … and then repeat this process over and over again without fixing the underlying problem.

Wrong VFD enclosure type

Industrial devices operate in various environments. Each setting presents unique dangers to electrical devices such as VFDs. Specifications for enclosure types from the National Electrical Manufacturers Association (NEMA) outline which can withstand each environment type. For instance, basic NEMA Type 1 enclosures are suitable for indoor settings that aren’t overly dusty. Such NEMA 1 enclosures have solid tops to protect the VFD from falling debris but have vented sides to allow cooling air to flow through to the drive. So if an environment calls for protection from liquids (whether it’s directed from a hose or falling from above) then using a NEMA Type 1 enclosure will surely lead to a very early dirt nap for the VFD. For hose-down applications, a NEMA Type 4 enclosure is more appropriate … and for outdoor rain protection, it’s better to use a NEMA Type-3R-enclosed VFD.

Unqualified personnel working on VFD

It’s not just a program to protect electricians’ jobs: Having unqualified or unknowledgeable personnel doing VFD wiring or preventative maintenance can spell doom for wonderful drive. Let’s just consider things that can go very wrong during initial wiring and operation of the drive.

Put 480 V on a 240-V VFD — Maybe it’s because some motors are dual voltage, or maybe it’s because some people are unaware, but VFDs are not dual voltage. It’s either 240 or 480 Vac here in (most of) North America. If you’re lucky and try to apply 240 V to a 480-V drive and discover the error before attempting to drive a motor, you may only suffer slight embarrassment. However, if you apply 480 V to a VFD manufactured to only handle 240 V plus 10% (~264 V) then you’ll quickly discover which device in the VFD is the weakest link.

Switch the VFD input and output power leads — Even though nearly every major VFD manufacturer defaults to input power terminals on the left and output power terminals on the right, it’s still a regular occurrence that said manufacturers’ repair departments receive damaged drives where the connections are reversed. Some of today’s VFDs can withstand being powered up with the power leads reversed, but the failure rate increases if the RUN button is pressed.

Unintentional single phasing – Most but not all of today’s VFDs can operate with single-phase input … especially in sizes below 100 hp. But to source three-phase power out to the motor while only getting single-phase input power, the internal components of the VFD must be overrated for the application — or else the load must be decreased. Either way, the VFD in single-phase applications must be oversized to endure the increased bus voltage ripple and increased input currents. If your true intent is to ensure the VFD “buys the farm” way before its time, then don’t oversize the drive for the motor in single-phase applications … and wait for the continuous faults and eventual drive failure.

This VFD was subject to fire. Avoid such situations to make your VFD last longer.

Miscellaneous VFD abuse and a final serious note

Other things that will also prompt a VFD to cross the river Styx include bashing it with a hammer, running into it with a forklift, lighting it on fire, or purposely short circuiting the dc bus by dropping quarters into the top of the drive.

Of course, this article presents VFD pitfalls in a tongue-in-cheek way. Few engineers would wish ill on their VFDs. These drives improve and simplify a vast array of automated processes. So as a public service, we offer the preceding methods of killing VFD as list of what not to do. With a little care and some reasonable forethought, your favorite VFD will still be there when you finally “leave the building” — and by that we mean retire.

Elmo Motion Control at IMTS: Making smart machines smarter

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At IMTS 2018, Elmo Motion Control will showcase its new Double Gold Twitter ultra-small servo drive and its Platinum Maestro motion controller, which controls up to 256 axes. These motion products suit the most demanding applications in the era of Industry 4.0.

The new Double Gold Twitter is among the smallest STO-certified (IEC 61800-5-2, SIL-3) servo drives on the market. It delivers to 10,000 W and weighs only 1.2 oz — with continuous currents of 160 A (80 V) and 140 A (100 V).

Platinum Maestro motion controller

This miniature drive can mounts on moving loads, on motors, or inside motors to help engineers save space, improve machine performance, reduce cabling, and eliminate electrical cabinets, all while delivering unprecedented power.

Visit Elmo Motion Control at IMTS 2018 (IAMD) in Chicago at Booth #134142 to see these and other innovative motion solutions and capabilities for efficient and cost-effective smart machines.

Also — learn how smart drives and controls can help improve machine performance while enabling manufactures to achieve more for less at an Elmo Motion Control presentation.

The Paradox of Smart Manufacturing — which won the 2018 first prize SPS Roberto Maietti Award (recognizing thought-leading abstracts) will be presented in a session — Challenges of automation: Efficiency and flexibility. Join Elmo product & sales enablement manager Tomer Goldenberg for this live presentation on Tuesday, September 11, 2018 at 3:15 pm (W196-A).

Also be sure to visit www.elmomc.com.

NORD SK 02040.1 — new gearmotor offering with high-strength aluminum-alloy features

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With the new SK 02040.1 the NORD DRIVESYSTEMS range now includes a high performance, light, and versatile helical worm gear unit for myriad applications.

Manufacturers across a several industries will benefit from NORD DRIVESYSTEM’s newest helical-worm gear unit. The redesigned two-stage SK 02040.1 is suitable for conveyors in food and beverage, bottling, manufacturing, warehousing and packaging applications.

SK02040 line of Nord high-strength aluminium alloy gearmotors delivers significant savings over competitive products

The NORD SK 02040.1 gear unit is made from high-strength aluminum alloy. This one-piece die-cast aluminium UNICASE housing provides maximum strength and rigidity with low weight. In addition, a new universal mounting design offers significant customer advantages.

“The NORD gear unit provides nearly 900 lb-in of torque – which is suitable for countless conveyor and manufacturing applications. It can be quickly installed and offers a smart universal foot flange housing, and accessories for foot, flange or torque arm mounting. Plus, the aluminum is more than 30% lighter than cast iron,” said NORD product manager Jim Alt about the SK 02040.1 design.

“By using aluminum, the NORD SK 02040.1 helical worm gear unit is priced significantly below the product it´s replacing … and we expect customers could see double-digit savings compared to competitive products,” he added. The gear unit can also be ordered with NORD’s nsd tupH sealed surface conversion process, which provides comparable benefits of stainless steel at a 30 to 50% cost savings.

The new SK 02040.1 gear unit offers a wide power range from 0.16 to 1.5 hp (0.12 to 1.1 kW) and delivers output torque up to 885 lb-in. (100 Nm). The wide range of speed ratios (5.3:1 to 330:1) enables optimum adaptation to customer requirements.

All NORD helical worm products are available with solid, keyed or keyless hollow bores. The SK 02040.1 geared unit also offers input options to a variety of motors, including direct mounting, NEMA and IEC. The new SK 02040.1 unit is a drop-in replacement to the previous SK 02040 cast iron product. For a product sample, product information or a prototype, contact  local NORD sales representative at nord.com/locator.

To configure NORD helical worm units online, visit hubs.ly/H0cQ-NW0.

28 mm (1.10 in.) planetary and harmonic gearheads for dc input αSTEP AZ series stepper motors

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Oriental Motor now offers new planetary and harmonic gearheads for the AlphaStep AZ Series DC input stepper motor in 28 mm (1.10 in.) frame size.

The AlphaStep AZ Series stepper motors are part of the Hybrid Control System and delivers high efficiency and low vibration together with Oriental Motor’s newly developed Mechanical Absolute Sensor for absolute-type positioning. This breakthrough mechanical sensor doesn’t need a battery nor does it rely on external sensors, eliminating extra steps and parts and reducing costs in the application design process.

The AlphaStep Hybrid Control System constantly monitors the motor’s position, allowing for the benefits of open loop control while providing the assurance of closed-loop performance. The AlphaStep Hybrid Control System product line-up features the AZ and AR Series stepper motors as the common motor and driver for round shaft, geared and actuator motion control solutions.

Both of the new 28 mm gearheads have two gear ratios: the planetary gearhead is 7.2 and 10:1 while the harmonic gearhead is 50 and 100:1. Available with built-in controller or pulse input type driver which efficiently reduces heat generation. For multiple axis application, Oriental Motor offers a 2, 3 or 4 axis AZ Series multi-axis driver with built-in EtherCAT communication.

For mote information about Oriental Motor’s AlphaStep Hybrid Control System, the deep link to the page on orientalmotor.com on closed-loop stepper motors.

More details on the trend towards Ethernet-based networking protocols

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In a recent survey of industry experts, many mentioned Ethernet-based networking protocols overtaking traditional fieldbuses.

Recall that industrial communication protocols (including those based on Industrial Ethernet) are messaging systems for automated installations. Some fieldbuses are more reliable than nondeterministic Ethernet offerings, but Ethernet speeds now lead.

“Some old bus systems have data rates in the range of 1 to 20 Mbit and no real-time reaction,” said Horst Messerer, HELUKABEL data, network, and bus technology sales manager. “Certain types of manufacturing can tolerate these rates … so bus protocol won’t go away entirely — but they’re seeing reduced market share.”

In fact, industrial Ethernet-based networks now connect some 40% of industrial communication networks.

“That’s why more bus systems are being replaced with Ethernet-based equipment,” said Messerer. “The advantage of Ethernet is its faster data rate — with a minimum of 100 Mbit — which lets industrial-automation manufacturers view manufacturing and production process data in real-time. Having this kind of data quickly allows for improved reaction time to optimize processes for higher output per hour.”

Another benefit is that even though older variations such as 802.3c is slower than 802.3ab (at 1 Gbit/sec, which is called GbE) all use Cat5e cable. That makes Industrial Ethernet implementation easier. Both Cat5 and newer Cat6 cables for Ethernet work with Gigabit Ethernet, though Cat6 Ethernet cable is displacing the former.

“We’ve seen continued robust interest in both Cat5 and Cat6 flat cables,” said Rich Buchicchio of Cicoil Corp. “Our versions of these cables typically go in applications that benefit from high cable flexibility and durability to survive extreme environments better than common versions of these Ethernet cables.” The cables meet (and typically exceed) platform requirements.

Besides speed, other reasons for Ethernet’s rise include its ease of use, and ubiquitous design; multi-protocol network acceptance; familiarity thanks to commercial off-the-shelf (CotS) Ethernet; and consolidation of network-interface hardware. Plus unlike traditional device and fieldbus networks (that can have multiple physical layers) Ethernet networks run on one.

Controls and related motion hardware often dictate which fieldbus communications an installation will use.

“We continue development of integrated motors that can be powered over Ethernet (PoE),” said Eric Rice of Applied Motion Products. “Combining power and Ethernet over a single cable is an excellent example of the evolution of integration in motors, drives, and industrial Ethernet communications.”

PoE-enabled integrated motor offerings from the manufacturer include NEMA 14 and NEMA 17 frame motors.

Traditional industrial components feature Ethernet connectivity for an increasing array of functions. “Today, there are scalable I/O options for PLC control … and new hardware to communicate with remote I/O includes multi-Ethernet products to cover major Ethernet such as SERCOS, EtherCAT, PROFINET, and EtherNet/IP,” Joaquin Ocampo, product manager of motors and drives at Bosch Rexroth.

In fact, five real-time protocols — CC-Link, EtherCAT, EtherNet/IP, PROFINET, and SERCOS III capitalize on Ethernet advantages and deterministic networking.

The CC-Link protocol (supported by the CC-Link Partner Association) includes field-device, controller, and information networking and gets speeds to 10 Mbps at 100 m. Versions include CC-Link, CC-Link Safety, CC-Link/LT, and CC-Link Industrial Ethernet (IE) Control and Field. One CC-Link standard is a Seamless Message Protocol to let Ethernet-ready devices work on CC-Link IE networks. A new version of a Control and Communication System Profile (CSP+) simplifies integration of engineering tools and device profiles (in part by outlining the data necessary for setup and operation of CC-Link-compatible devices). Automation-component manufacturers primarily offer CC-Link functionality for servomotors, drives, robots, digital and analog I/O modules, and controllers including PCs and PLCs.

The Ethernet for Control Automation Technology (EtherCAT) protocol uses Ethernet and twisted-pair or coaxial cables with BNC adapters over distances to 1,000 m and optical cable beyond that. It gets Ethernet transfer rates and can control up to 65,535 nodes. Data processing through dedicated software and hardware allows deterministic communications. EtherCAT accommodates any topology and handles 1,000 I/O points in 30 μsec — capable of communicating with 100 servo axes in 100 μsec. Axes get values and control data and report position and status. A simple version of an IEEE 1588 distributed clock technique synchronizes axes with less than 1 μsec of jitter.

Shown here is a maxon motor EPOS04 Compact 50/8 EtherCAT smart drive-controller for programmable positioning.

Ethernet/IP is an industrial application-layer protocol for communication between industrial controls and I/O. It uses standard IEEE 802.3 TCP/IP and communications; Ethernet hardware pairs with TCP and UDP ports. Certain permutations enable synchronized and deterministic multi-axis motion control.

In fact, this and other industrial-Ethernet standards drive many product-development decisions that Applied Motion Products makes. “This year we enhanced our support for EtherNet/IP networks by introducing a set of improved Add-On Instructions for Rockwell’s RSLogix 5000 software,” said Rice. “We also introduced a new family of cost-effective motor drives for EtherCAT networks … and have begun development on drives and integrated motors for use on PROFINET networks,” he added.

Serial Real-time Communications System (SERCOS) is an open protocol for serial communication of closed-loop real-time data — over Ethernet cable for SERCOS III. Specifically for motion controllers, drives, actuators, sensors, I/O, the IEC-standard protocol closes servo loops in the drive to reduce motion-controller burden (and synchronize more motion axes than otherwise possible). Such closing of servo loops also avoids delays between motion controls and drives.

SERCOS III gets deterministic bidirectional real-time motion and control. It also enables higher-level I/O and transmission of conventional protocols over one Ethernet network in parallel with SERCOS real-time communication — with cycle times to 31.25 μsec.

PROFINET is from the same organization from the same organization that gave the motion industry PROFIBUS (PROFIBUS & PROFINET Intl. or PI) PROFINET use of Ethernet means larger messages, better bandwidth, and theoretically unlimited address space … as well as avoidance of network collisions. Deterministic communications are possible through real-time and isochronous real-time (IRT) operation. The latter gets update times down to 250 µsec, while PROFINET IRT gets them down to 31.25 µsec for synchronizing networked components.

Of course, industry-specific communication buses endure and even grow, as connectivity imparts design sophistication even to turnkey operation.

“Products with integrated industrial communications protocols simplify operation,” said Laura May of Thomson Industries. “For example, integration of J1939 CAN bus communications — most commonly used in mobile off-highway markets — means a system can programmed to let each of its actuators run with real-time awareness of speed and position of other actuators — enabling self-adjustment and deploying multiple actuators to handle heavy loads,” May added.

She added the manufacturer has work in progress to better support protocols commonly used in plant-floor automation.

Of course, an ever-growing (and cost-effective) array of gateways simplify network connections where J1939 CAN (and other buses) must interface with Ethernet. It’s common for fieldbus components to connect to Ethernet blocks for connectivity via Cat5E cable and Ethernet RJ45 connectors. Ultimately, Ethernet can even facilitate IIoT functionality to connect enterprise-level systems with machine, I/O, and device-level operations.

Ethernet-driven cloud-based IIoT along with (IEEE-802-compliant) wireless variations unify data streams for:

  • I/O and motion communications and controls
  • Safety functionality to protect equipment and personnel
  • Diagnostics, machine-condition monitoring, and energy management
  • Final product tracking and documentation of plant-operation statistics

 

“One of three smart Han modules available is the Mini Ethernet Switch Module,” said Mark Kojak, V.P. of product management and business development in the Americas at Harting Inc., manufacturer of interconnect components. This module incorporates a four-port Ethernet switch within the connector. The module can replace or reduce the port count in systems needing a multi-port Ethernet switch … and excels in systems that use a daisy-chaining architecture.

Case study: Slip rings use CC-Link IE for gigabit data transfer

By John Wozniak, P.E. | Manager of CC-Link Partner Association (CLPA) Americas

Manufacturer of mobile electrification and data transfer systems for industrial machinery Conductix-Wampfler now uses CC-Link IE open gigabit Ethernet (GbE) for high-performance connections in its slip rings. Traditionally used to supply continuous power and data communication to equipment on rotating assemblies, the slip rings are for new and existing machinery needing Industry 4.0 data connectivity.

Conductix-Wampfler specializes in power, signal, and data-transmission systems for container handling, tunneling, mining, and bulk material handling. Their slip rings find use on rotating arms and gantries, cranes, wind turbines, manipulators, and cable reels.

As a CLPA member, Conductix-Wampfler has technical specifications to develop compliant product … even for custom connectivity solutions that work with Ethernet up to 1Gbps.

“Our slip ring technology excels in everything from industrial machinery to theme park rides … and we see need to transfer an increasing amount of data in a secure and easily accessible manner,” said product manager at Conductix-Wampfler Matteo Mosconi. So the company joined CLPA to focus on CC-Link IE because it’s the first and only open protocol that works at 1Gbps with real-time characteristics — and the organization that supports it offered the technical support Mosconi wanted.

“Slip rings certified for CC-Link IE can transmit power … as well as data at very high transfer rates.”

Founded in 2000, CLPA is an international open-network organization with more than 3,000 members (and the leading open industrial-automation network technology in Asia) dedicated to technical development of CC-Link open automation networks. Main activities include the development of CC-Link IE and CC-Link technical specifications; conducting conformance tests and development support. CC-Link IE is an open GbE solution for Industry 4.0 automation with unmatched bandwidth.

CC-Link Partner Association (CLPA) member Conductix-Wampfler used CC-Link IE open GbE technical specifications to develop compliant slip rings.

PTDA Foundation endorses Manufacturing Day 2018

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Manufacturing Day, scheduled for October 5, 2018, presents an opportunity for power transmission/motion control (PT/MC) distributors to support their manufacturer suppliers and raise their own visibility as an employer within their own communities.

PT WORK Force, an initiative of PTDA Foundation to help PT/MC employers with employee recruitment, hiring and retention, has three new volunteer committees focused on enabling PT/MC employers to recruit new employees and attain a sufficient, vibrant workforce. They are advocating that PT/MC distributors participate in Manufacturing Day 2018.

PT WORK Force Outreach Committee Chair (and president of Bishop-Wisecarver) Pamela Kan has been participating in Manufacturing Day events for the past six years, since its beginning.

“This is a great opportunity for manufacturers and distributors of power transmission/motion control products to open their doors to the public and show students, educators and parents that a career in the PT/MC field offers a variety of things to do, a good income with benefits and meaningful work,” said Kan. “There are so many people who don’t know what we do and it’s up to us to educate them. I can’t think of a better way than inviting them into workplaces and showing them what we do.”

PT WORK Force has signed on as an endorser of Manufacturing Day 2018. The PTDA Foundation has long advocated for industrial distributors to host company tours for students and community members as well as attend classroom talks and career fairs to raise awareness of the PT/MC industry as a career field in communities across North America.

With many manufacturers opening their doors to the community on or around October 5, distributors are encouraged to join in the fun by visiting the Manufacturing Day website at www.mfgday.com to find resources and to sign up to host an event. Also be sure to visit ptda.org/PTWORKForce.

What’s the difference between an EC motor and a BLDC motor?

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Deciphering motor terminology can be frustrating, especially when comparing the operation and performance of various motor types. For example, some motors are characterized by their speed (synchronous or asynchronous) while others are characterized by their commutation method (brushed or brushless). And then there’s the issue of whether the motor is operated with AC or DC power — but even this seemingly simple distinction can be misleading. Case in point: “DC” motors use a DC power supply, but the current is switched to AC in order to feed the motor windings, so some experts argue that these motors should, technically, be placed in the same category as motors that run on AC power. And just when you think you have the terminology and specifications all figured out, along comes another name or acronym, added to the mix.

In the motion control world, a relatively new motor distinction that is becoming more widespread is the term “electronically commutated,” or “EC,” motor. So how does this “new” EC motor fit into the existing hierarchy?

The short answer is, EC motors are not a new technology. They are simply permanent magnet brushless DC (BLDC) motors that are being distinguished by their method of commutation (i.e. electronic) rather than by their physical characteristic of lacking brushes. These motors, whether referred to as “brushless DC” or “electronically commutated,” have a permanent magnet rotor with a wound stator. Electronics determine the sequence for commutation, or energizing of the stator windings, based on the rotor position, which is most often provided by either three Hall sensors or a rotary encoder (although there are methods of determining rotor position without additional feedback devices).

EC motor

The brushless DC (aka EC) motor on the right uses electronics to determine the sequence for energizing the stator windings, based on rotor position provided by Hall sensors or an encoder. The brushed DC motor on the left is mechanically commutated via brushes and a commutator.
Image credit: Think RC/JP Commerce, LLC

A quick google search of “EC motor” or “electronically commutated motor” reveals that this terminology is used extensively in the HVAC and refrigeration markets, especially for equipment such as fans, blowers, and compressors — all of which have traditionally been powered by AC induction motors.

Recall that AC induction motors operate via AC current provided to the stator, which creates a rotating magnetic field. This field induces a current, and therefore a magnetic field, in the rotor. The stator and rotor magnetic fields rotate at different speeds (aka “asynchronous”) to generate torque. While inexpensive and easy to operate, AC motors’ two main operating characteristics result in reduced efficiency when compared to BLDC, aka EC, motors. First, inducing current in the rotor windings increases power consumption, and second, the difference in speed between the magnetic fields — known as “slip” — causes heat generation. This inefficiency has not gone unnoticed by the United States Department of Energy.

EC motors

EC (aka BLDC) motors have higher efficiencies than AC induction motors, in part because EC motors don’t experience slip between the rotor and stator rotating fields.
Image credit: H.C. Nye Co.

BLDC, or EC, motors have high efficiency over a range of speeds, rather than a high peak efficiency at a single speed.

EC motor

Stricter, and more specific, energy efficiency rules from the DOE have made EC motors the preferred choice in HVAC and refrigeration applications.
Image credit: ebm-papst

This report, published in 2013, details the Department of Energy’s analysis of power consumption in the U.S. The report shows that residential and commercial end uses account for approximately 39 percent of annual energy consumption, with the industrial sector accounting for approximately 32 percent. (Transportation makes up the remaining 28 percent.)

The report then goes on to discuss opportunities and barriers to reducing overall energy consumption — primarily by increasing the efficiency of motor-driven systems and components in commercial and residential applications. One of the key ways to achieve this is by replacing the motors traditionally used in these applications — primarily AC induction motors — with higher efficiency motors — namely, EC designs.

This statement from the report explains…

For almost all equipment types in both the residential and commercial sectors, the market is transitioning to permanent magnet motor technology for the highest-efficiency models within each category. Permanent magnet motors are becoming increasingly cost-effective based purely on simple payback period. They also offer other non-energy benefits such as reduced noise and the ability to reach higher rotational speeds.

In fact, the DOE’s most recent Small Motor Efficiency Rule and Integral Horsepower Motor Rule, together with various DOE rules specific to HVAC and refrigeration equipment (think blowers and compressors) as well as to pumps and fans, have compelled motor manufacturers and equipment OEMs to transition from AC induction motors to EC motors in many types of applications and equipment.

So, if an EC motor is really just a BLDC motor by a different name, why add another term to the already complex hierarchy of motor nomenclature? One reason may be to avoid confusion for those who are most familiar with AC motors and might associate any DC motor with the brushed designs that dominated the DC motor market for many years. Using the term “electronically commutated,” rather than “brushless DC,” makes it less likely that users will confuse the modern, high-efficiency, long-life motors with brushed designs, which suffered from poor efficiency, frequent maintenance, and reduced service life.

Another reason can be found in the DOE publication cited earlier. There, the agency specifies (emphasis added):

In general, ECMs refer to low horsepower BLDC motors that have integrated drives and controls and are commonly found in HVAC applications.

Here, the agency makes a distinction between permanent magnet, brushless DC motors with separate drives and controls (BLDC motors) and those that have integrated drives and controls (EC motors). However, some manufacturers and OEMs clearly use the terms “EC motor” and “BLDC motor” interchangeably when describing a permanent magnet, brushless DC motor, regardless of whether the drives and controls are integrated into or separate from the motor.

Since numerous manufacturers of EC (BLDC) motors supply not only to the HVAC and refrigeration markets, but also to the motion control market, it’s no surprise that the terms “electronically commutated motor” and “EC motor” are permeating the motion control lexicon. And if it helps reduce the confusion between BLDC, PMSM, BLAC, and the plethora of other motor names and acronyms out there, that can only be a good thing for those of us tasked with decoding the jargon to evaluate and specify the best design for our application.

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