If there’s one trend that’s prevalent in motors of all kinds, it’s the theme of increasing performance, more specifically a trio of highers: higher efficiency, higher power density and higher torque density.
These are incremental improvements in motor performance that are at least partly driven by the Department of Energy (DOE) energy efficiency requirements, said Dan Jones, consulting motor designer and president of Incremotion. For instance, the DOE has been pressing the ac induction motors ranging from 1 to 500 hp. The DOE did not increase the efficiency requirements beyond premium efficiency (IE3) in their recent review last year, but a number of U.S., Brazilian and European motor manufacturers have moved to brushless PM motor types to achieve higher motor efficiencies in the IE4 category, added Jones.
ABB provided the market with a different solution. They developed a family of synchronous motors with which they’ve achieved the IE4 motor efficiency levels. The major problem for brushless PM motors has been competitive pricing against the similar sized ac induction motor. The ground rules for achieving a range of higher motor efficiencies requires a Variable Frequency Drive (VFD) to achieve good efficiencies over a range of application loads. While a large number of smaller HVAC applications can use plug-in-the-wall power, a major trend in industrial applications is using VFDs with the induction motors.
As far as higher power density goes, axial flux motors (PM brushless) are high-power density motors that have been used in hybrid cars primarily because of their high power capability. Part of their secret to success is that they operate at load speeds approaching 10,000 rpm. The axial flux motor also develops about 30 to 40% more torque than a similar sized radial flux motor. The combination of the two aforementioned elements determines the axial flux motor’s high power density.
The best motor type for torque density is the transverse flux motor, said Jones. It uses a 3D magnetic circuit, and only a few motor companies are currently building this brushless PM configuration. It’s a complicated machine that can double the shaft torque normally achieved by a conventional brushless PM motor. There is a speed limitation of most current models under 1,500 rpm and some as low as 300 rpm load speed.
Another trend is the increasing call for specialization of motors for specific applications. “It has become increasingly important for motor designers to get as close as possible to the end application to optimize design and manufacturing,” stated Matt Morrow, business development manager with Portescap. “Examples of this include new materials, construction, magnets and manufacturing processes, each of which deliver a better product to the application, and ultimately to the end customer,” he added.
One area where specialization is especially important is the medical industry. “Medical device manufacturers are helping drive change in motor design,” said Walter Hock, director of product management at Portescap. Patient comfort and discretion is driving wearable insulin and drug delivery systems design. “Motor manufacturers help meet this market need by delivering high-precision motion from smaller, more efficient motor solutions that minimize device size and weight and improve battery life,” he added. To do this, they have to change the way they design miniature motor coils, transmission components and high-accuracy feedback devices that deliver required accuracy and efficiency.
Furthermore, said Hock, “healthcare providers are focused on reducing the overall cost of care. This places an intensified emphasis on total cost of ownership of surgical instruments, which pushes motor design in two seemingly opposing directions.” Cost conscience healthcare providers want longer device life and therefore a motor designed to withstand more sterilization cycles. But, new device designs expose the motor to harsher, more diverse environments during the surgical procedure. In both cases, this has challenged motor design teams to innovate improvements in material selection, motor sealing and over-molding techniques.
As far as motor manufacturing goes, the single biggest change in manufacturing, particularly in the medical industry, has been a strengthening of processes and controls, providing ongoing traceability and accountability for quality. As the FDA has placed more stringent requirements on medical device manufacturers to control and monitor second and third-tier suppliers, there has been an increase in regulatory scrutiny on motor manufacturers. Based on this increased scrutiny, motor manufacturers are incorporating further process controls into the design process. This translates into better process controls on the manufacturing side, which allows it to become an extension of the medical device manufacturer. The output is a superior manufactured product.
Beyond general technology trends for motors of all kinds, we asked some top manufacturers of specific motor types what trends they’re seeing in particular motors, such as servomotors and steppers, among others. Below are their responses to our query.
Technology trends in servomotors
Bill Sutton • Strategic Sales Manager • Kollmorgen
1) What are some of the key technological advances that have taken place in the area of servomotors?
We’ve developed a servomotor and associated cables that can be used in washdown environments without any restrictions on cleaning methods. Cleaning solutions ranging from 2 to 12 pH can be applied to the motor, cables and connectors without restriction. High-pressure spray up to 1,500 psi can be used on the motors and associated cables and connectors without restriction, as well. The technical advances that allow this are the application of compatible materials that can handle the tough environment without degradation; development of a venting design that allows for motor heating and cooling cycles without creating relative pressure differences between the inside and outside of the motor, making the motor much more resistant to ingress of moisture or cleaning solutions; and a little bit of motor design magic that keeps the motor from being too big and expensive. In addition to being durable, the motors are designed to meet hygienic machine design standards making them easier to clean. The primary hygienic features are a 32-µ surface finish including laser annealed nameplate, no metal-to-metal seams, no external hardware, no flat surfaces and no nooks to harbor pathogens.
2) What industries are directly spurring changes in the design of servomotors?
The food processing industry is driving the design of motors that better fit their needs. We surveyed more than 80 food processing companies, and the overwhelming response that we received was the need for electric motors that could be cleaned without failure and that were easier to clean, requiring less time and effort to ensure sanitation was achieved. The need for a more durable and cleanable design has existed for a while, but existing designs for stainless-steel servomotors were big and expensive and many times were not significantly more reliable than standard servomotors. So, the pent up demand plus the anticipation of the effect that the Food Safety Modernization Act (FSMA) will have on sanitation standards and machinery design is driving this market.
Technology trends in stepper motors
Clark Hummel • Director of Product Management • Schneider Electric Motion USA
1) What technological advances in the last few years would you say have improved the performance of stepper motors and helped foster their use in new kinds of applications?
First, the advent of integrated motion. Combining the stepper motor, drive, controller and encoder into one package that is easy to mount, wire and configure has proven to be a great advantage to machine builders. It reduces machine size, cost and complexity, while increasing the ease by which a system can be integrated.
Second is the creation of advanced control techniques, such as Hybrid Motion Technology (hMT). These controls maintain stepper motor advantages—high torque density, lack of jitter at standstill, no tuning requirements, cost effectiveness and more—while delivering typical servomotor advantages, such as no loss of synchronization, torque control capabilities, reduced heating and energy use.
2) Have any particular industries been responsible for improvements or changes in stepper motors in recent years? Are any particular industries increasing their use of motor drives? If so, can you say why?
Stepper’s strong position in biomedical/life science markets is longstanding. With recent improvements in integrated motors—including industrial connectors, IP ratings, hMT and the ability to reside on popular fieldbuses—steppers can proliferate in more industrial markets, such as packaging, food and beverage, and automotive.
3) Is there any particular motion control application you’ve seen recently that would have been impractical, say, five years ago?
Torque Control, a feature of Hybrid Motion Technology, was not previously possible with stepper motors. Torque Control supports applications such as winding, capping and clamping that were previously impossible to implement due to the motor’s loss of synchronization and stalling. Steppers are now being used in these applications every day.
Technology trends in linear motors
Peter Zafiro • LinMot USA
1) What are some of the key technological advances that have taken place in the area of linear motors?
Continued improvements in communication interfaces, the desire for better position control and the need for greater plant efficiencies are the key market drivers to using more electric actuators. These trends are definitely true for linear motor direct drive systems and now even in applications where induction motors and pneumatic cylinders were predominantly used.
The advent of Ethernet communications is driving the desire to put servo axes on the plant network. This provides significant data that plant managers can use to improve their productivity and throughput. Once this occurs, the next step is to get more flexibility in positioning and drive up productivity. Thus the drive to introduce servo axes in traditional induction motors and pneumatic applications. The last step in this process is to drive out cost and increase efficiency, which leads toward direct drive technologies, like linear motor driven actuators.
Eliminating belts, screws, cams and gears increases efficiency and reliability while providing higher throughput. In the end, it is all about up time and what a plant manager can do to decrease his weaker points in the production process. Mechanical drive systems bring limitations due to wear and have decreased performance characteristics. Decreasing the number of mechanical connections in almost all cases increases throughput and uptime.
There is a lasting benefit with direct-drive linear motor systems: energy savings. This is being taken advantage of heavily in Europe, and is just in its infancy here in North America. Even in some very traditional pneumatic applications, like a point-to-point positioning application, the direct drive tubular linear motor system can provide significant return on investment. The savings then flow to the bottom line in reduced energy costs and increased uptime.
2) What industries are you seeing that are spurring changes in the design of linear motors? Also, what industries are contributing to changes in linear motors?
The packaging industry has been a key driver in tubular linear motor development. Many pick-and-place applications are being upgraded to direct drive technologies simultaneously increasing productivity and decreasing energy costs. Another industry that is starting to affect linear motor development is the medical industry. The advantages of less mechanical connections mean cleaner running production lines. The ability to handle tough environmental requirements have driven significant developments into all stainless-steel IP69k tubular linear motor technologies. Many of the tough food processing and manufacturing environments are also a key player in this clean direct drive technology.
3) Are there any notable changes in manufacturing and/or distribution that have impacted linear motors? If so, what are they and how have they impacted designs?
Over the last ten years, many linear motor production processes have gone to mainstream production and thus allow for lower cost plant implementation. Another area that has evolved is logistics. Just shipping product from anywhere on the globe has gotten easier.
In North America, there has been a big push by the key automation distribution partners to increase their network and control knowledge, allowing the end customers and OEMs to concentrate on their core competences: producing the end product and/or manufacturing machines. These automation distributors are able to provide significant assistance to the plants and OEMs helping them achieve higher production goals and more efficient plant operations.
Technology trends in fractional-horsepower motors
Ed Tullars • Sales Manager • Groschopp
1) What are some of the key technological advances that have taken place in the area of fractional horsepower motors?
Mostly, the controls, electronics and sensors have come down in price, which has increased the demand for electric motors. As for changes in the motors themselves, one of the most prominent is that the cost of rare-earth material has improved, making different motor types easier to manufacture with more power.
2) What industries are you seeing that are spurring changes in the design of fractional horsepower motors? What industries are contributing to changes in fractional horsepower motors?
Really, a lot of industries are switching to electric power. You see this in the cars that GM and Ford and others are designing. There’s also a conversion from, let’s say, hydraulic systems to electric systems. Electric power is cleaner, easier and sometimes safer to use. Electric power equipment is also more accurate for robotics applications. Wherever we look, we’re seeing demand for more electric and automated products.
3) Are there any notable changes in manufacturing and/or distribution that have impacted fractional horsepower motors? If so, what are they and how have they impacted designs?
One notable change we see is more competition in the market driving a more competitive market place. It’s also harder and harder for some customers to find the correct motor for their application. It truly takes a trained person to get the correct motor speced for the correct application, based on speed, torque, stall startup torque, IP rating, duty cycle, current draw, and so no. In the past, you speced a motor that would not blow the fuse. Today we have to work with all the parameters to match the customer desired equipment needs.
Technology trends in DC Motors
Chad Hammerly • Motion Control Solutions • Business Unit Manager Rotary Products (Pittman)
1) What are some technological advances that have improved the performance of brushed and brushless dc motors or helped them get into new applications over the last few years?
One of the biggest and ongoing changes we’re seeing is the integration of controls in brushless motors.
2) What industries are spurring changes in the design of dc motors?
Medical and dental instrumentation, power tools, autonomous robots, drones and unmanned aircraft. Also, general factory automation is using a great deal of smart dc communications controls. High flexibility reduces costs and allows for faster installations.
3) Has the manufacture or distribution of dc motors, linear motors and integrated actuators changed over the last few years?
Yes. The Internet has allowed convenient features, such as web-based configurations. For instance, our Pittman Express program allows customers to go online and order a selection of products that are available to ship within 24 hours.
4) The range of miniature applications is expanding, with the use of miniature motors expanding with it. Why do you think miniature designs are so promising from a design standpoint?
Invasive surgeries and remote surgical robotics are applications where miniature motors are expanding due to the need for power and precision in a small package.
Also, evolutionary trends are requiring products to be lighter, more powerful and portable. We’re also seeing trends where smaller motors are being requested to aid in ergonomics for applications. For instance, smaller hand drills to fit smaller hands.