Motors - Motion Control Tips

How can a universal motor operate on either DC or AC supply?

May 15, 2018 by Danielle Collins Leave a Comment

A universal motor is a series-wound motor — meaning that the field and armature windings are connected in series — and is mechanically commutated with brushes and a commutator. Although its construction is very similar to a series-wound DC motor, a universal motor incorporates several modifications that allow it operate properly on either DC or AC power supply.

For proper operation with AC supply, a universal motor incorporates a compensation winding, in series with the armature and field winding.
Image credit: circuitglobe.com

When the motor runs on AC voltage, the alternating flux causes a reactance voltage, which limits the current to a much lower level than would be produced with DC voltage. To limit the effects of this armature reaction, the universal motor uses a compensation winding, which is installed in the slots of the stator, 90 degrees electrical from the main field winding and connected in series with the armature and field winding. (This arrangement is referred to as “conductively compensated.”) The current flowing in each coil of the compensating winding is in a direction opposite to the current in the corresponding armature loop near it. The winding of equal coils in opposite directions produces a cancelling effect that reduces inductance, and therefore, reactance.

AC supply also induces more significant eddy currents than are produced when the motor operates on DC supply. To curtail eddy current losses, universal motors use laminated cores (rather than solid iron), which increases their resistance and reduces eddy currents.

Armature reaction is the interference of the main field flux caused by the armature flux. This distortion and weakening of the main field flux changes the location of the magnetic neutral plane, which is the axis along which the brushes should be placed.

Armature reaction changes the location of the magnetic neutral plane, which is the axis along which the brushes should be mounted.
Image credit: Precision Microdrives Limited

It is because the armature and field windings are connected in series that a universal motor can operate with either DC or AC supply. Being connected in series means that both windings are supplied by the same source, so if the voltage source changes polarity, as it does with AC supply, both the armature and field currents also change polarity and the direction of torque does not change. (The direction of rotation is reversed by reversing the current in the field circuit.)

To reduce inductance in the armature, the current flowing in each coil of the compensating winding is in a direction opposite to the current in the corresponding armature loop near it.
Image credit: Festo Didactic

One of the primary benefits of a universal motor is its ability to achieve (theoretically) unlimited speed, with speeds up to 20,000 rpm in real-world applications. The speed-torque curve is essentially a straight line between stall torque (zero speed) and no-load speed (zero torque), meaning that as the load (torque) increases, the speed decreases. In fact, like a series-wound DC motor, running a universal motor with no load (zero torque) could lead to a runaway condition, where the speed increases until the motor begins to break apart. The converse of this phenomenon is that universal motors produce very good starting torque (high torque at low speeds).

A universal motor can produce extremely high speed at zero torque, but speed drops rapidly as torque increases.
Image credit: Groschopp, Inc.

This ability to run at very high speeds means that universal motors are good for applications that involve rapidly spinning components, such as fans, blow dryers, and vacuum cleaners. And their ability to produce high torque at low speeds makes them suitable for applications such as blenders and portable drills. Because they’re mechanically commutated, universal motors generally aren’t suitable for continuous-duty applications, due to brush maintenance and wear. The brushes also make them relatively noisy, so their primary areas of application are small consumer appliances.

Feature image credit: Groschopp, Inc.

How to design gearmotors for extreme ambient conditions

April 10, 2018 by Miles Budimir Leave a Comment

Following some straightforward advice on gearmotor design will help ensure your gearmotor works in the most extreme environments.

Gabriel Venzin
President
ABM Drives Inc.

Designing a gearmotor application is tough enough in more or less “normal” conditions, normal here meaning something like room temperature and stable or typical humidity and altitude. Throw that application into an extreme environment and the design gets more complicated. But it doesn’t have to be. For anyone designing a gearmotor application in extreme ambient conditions, there are some guidelines that when adhered to will help ensure that the design succeeds.

First, the basics
A gearmotor is a combination of a gear reducer and an electric motor. The two most important factors at the gearmotor output shaft are its rpm and torque. A right angle, straight or parallel shaft gearbox can be combined with a permanent magnet ac, ac induction, or brushless dc motor.

The gearmotor applications discussed here are not exposed to high-pressure water spray, such as in freezers, unheated facilities or enclosures. They’re used in applications such as forklifts and electric vehicles, lifting technology, construction equipment, packaging machinery, as well as dockside crane hoists, and trolley and bridge drives, among others.

The goal is to have the gearmotor operate for decades of exposure to extreme ambient conditions with low maintenance because they may not be easily accessible. There’s not much mechanically different in a gearmotor for extreme temperatures and altitudes; mainly it’s lubrication, duty cycles, heating or cooling considerations and construction materials selection. So these tips can be used to upgrade existing systems as well.

The typical types of gearmotors we’re talking about include hoist drive gearmotors, which lift loads between 3.2 and 40 metric tons. They are powered by a 2.5 to 38 kW asynchronous cylindrical-rotor motor with 3-stage parallel shaft gearboxes for lifting speeds of 4 to 8 m/min at drum diameters of 140 to 405 mm and 4/1 reeving. Typical pole-switching motors (8/2-pole) are used. Variable speeds are programmed with inverters for acceleration and deceleration ramps with extremely slow start and braking which minimizes load swings.

A good start is to review data on past extreme temperature conditions in which the application will be operating and any other unique conditions that may be relevant to the design. In the following sections we’ll cover temperature, altitude and humidity and the way these factors influence gearmotor selection.

A 3D CAD model of a gearmotor for extreme environments from ABM Drives.

Temperature

What happens to the gearmotor when the temperature drops to -40 C?
From -40˚ C (-40˚ F) to +60˚ C (+140˚ F) a meter of ductile iron expands 0.123 mm. That’s the temperature range we’ll be covering here.

Altitude is the other extreme we’ll be covering. For an internal combustion engine, the general rule of thumb is a 3 to 4% power loss for each 1,000 feet above sea level. So a 300 hp car at 10,000 feet would lose 30 to 40 hp. Less density means less compression. Less actual matter in the atmosphere (oxygen, nitrogen, and argon mostly) is being drawn into the cylinders, and therefore compression is less. For a gearmotor, that means less atmosphere to dissipate heat.

How to compensate for temperature extremes? (A standard temperature range is -20 to +40° C.)
A common extreme temperature swing is when a forklift moves from a -30˚ C freezer to a +40° C dock door. For both extremely cold (-40˚ C) to very hot conditions (+60˚ C) you’ll need to address the following.

Gearbox oil – Synthetic lubricants are used when mineral oils have reached their performance limit for frequent starts and stops, high loads, system shocks, low or high-temperature service, extended oil service interval requirements and reduced internal friction besides reduced operating temperatures. They also operate at higher temperatures without losing viscosity, forming residues and offering resistance to foaming. Petroleum products begin to degrade at or below +100°C, whereas synthetic hydrocarbon lubricants function well to +125°C. Synthetics offer extreme low-temperature advantages as well. They also have lower vapor pressures than petroleum products, an important factor in ensuring that the lubricant doesn’t break down. The chemical homogeneity of synthetic lubricants results in greater load carrying capacity, higher viscosity indexes, better lubricity, greater efficiency and extended serviceability than their petroleum-based counterparts.

Shaft seals – If the gearmotor remains at low temperatures for extended periods of time, upgrade motor shaft seals to NBR (elastomeric) material or use high-grade grease for shaft seal lubrication. Elastomeric materials are composed of a polymer, filler, processing aid, protectants, and curing agents. Many times standard oil seals are made of Nitrile or rubber and are rated for temperatures up to +125˚ C. If ambient or oil temperatures rise above this level, you will have to use higher performance materials.

Motor cooling fan – These should be made of aluminum, GGG (nodular iron) or special plastic material.

Gearmotor systems for demanding applications, such as dockside crane hoists, trolley and bridge drives, need to be engineered for many years of severe duty cycles that demand minimum maintenance.

For proper function and use in temperatures from -20° to -40°C
Housings – Switch end shield material from GG (grey cast iron) to GGG (nodular iron). Nodular ductile iron possesses high strength, ductility and resistance to shock. Annealed nodular ductile iron can be bent, twisted or deformed without fracturing. Its strength, toughness and ductility duplicate many grades of steel but have low-cost casting procedures similar to gray cast iron. Ordinary gray cast iron has a random flake graphite pattern. Nodular ductile iron has a few hundredths of a percent of magnesium or cerium in its formula causing the graphite to form in small spheroid “nodules” rather than flakes. They cause fewer discontinuities in the structure of the metal for a stronger, more “ductile” iron. You can also use aluminum if allowable stress is not exceeded.

Rotor shaft – Switch material from 1045 steel to alloy steel, e.g., 42CrMo4 or similar. 1045 is a low hardenability carbon steel with a typical medium tensile strength range of 570 to 700 Mpa or Brinell hardness range of 170 to 210. It’s characterized by fairly good strength and impact properties. 42CrMo4 Alloy Steel is chromium-molybdenum steel with high strength and hardenability. It has high fatigue strength and good low-temperature impact toughness.

Motor heating – This could be a heater jacket, motor heating bands or the winding could be powered to maintain a certain temperature (this is also used to prevent moisture build-up in high humidity environments). External heating jackets, covers or housings are often installed by crane builders because they also need to protect the gearbox and other components.

Junction Boxes – Switch from plastic to aluminum

Fan Shroud – Switch from plastic to sheet metal version

Brake Design – Completely enclosed instead of open design

De-rating Torque – It might even be necessary to de-rate the maximum acceptable gearbox torque or use a larger gearbox.

For proper function and use in temperatures from +40° to +60° C
Note that temperatures above this must be reviewed on a case by case basis and cannot be covered by simply changing certain components.

If the gearmotor is mounted inside an enclosure near combustion engines or other systems that generate heat or are exposed to direct sunlight, it will require internal motor components that have higher temperature ratings. High ambient temperatures can also negatively impact motor torque and direct sunlight will degrade sealing components.

Junction Box – Switch from plastic to aluminum

Fan Shroud – Switch from plastic to sheet metal version

Altitude

For proper function and use at high altitudes
Heat dissipation on the surface of motors and gear units decreases with altitude. The thermal performance is reduced due to thinner air. Typically rated installation altitude is a maximum of 1,000 m above sea level. For higher altitudes, you should consider the following.

Verify the actual duty cycle of your application and ask yourself is a continuous duty motor really needed here? If it turns out that the application requires the same duty cycle as the rating of a motor at 1,000 m above sea level you can install a larger motor or add forced-air cooling to compensate reduced cooling capacity provided by the thinner air. In many cases, it makes sense to discuss possible options with the motor OEM.

A word about duty cycles
Duty cycles do not only impact the motor performance rating, e.g., a continuous duty cycle S1 motor will provide a higher output if it’s used at an S3 intermittent duty cycle, but also especially for gearboxes used in extraordinary applications where torque peaks and system shocks are possible. For such situations, it’s critical to carefully determine what duty cycle and what peaks/shocks per a specific time period are experienced so the engineering team of the motor/gearbox OEM can select and recommend a suitable drive system. So even if the application does not have a high rated torque and duty cycle requirement, other operational factors could result in the need for a much larger and stronger geared motor to be required to assure a satisfactory service life. And as a final word, always inform the motor OEM if your application is being used in extreme ambient conditions – this can be a game changer.

More information about recommended service lives for different applications have been published by the American Gear Manufacturers Association (AGMA.) These duty cycle recommendations have been determined from the experience of many gearmotor manufacturers. AGMA standard 6009 lists many applications by a service class (I (1 to 1.39), II (1.40 to 1.99), III (2 and above)) with class I being the simplest applications and class III being the hardest. Typically the total duty cycle for an application will take into account ambient temperature, cyclic duration, mass acceleration, operating time, and cycles per hour.

Wind turbine pitch drives are engineered for decades of continuous duty cycle that demand minimum maintenance and must satisfy the toughest requirements for reliability and durability.

How to determine duty cycle
First, you need to establish a target life. Not the calendar time, but the operating time. You need to know the duty cycle of the application during operation, and the number of hours the machine operates during the day.

As an example; a gearmotor drives a conveyor in short bursts, 2 minutes at a time, with 2 minutes off before repeating, over and over, during two 10-hour shifts, five days a week. You need it to operate trouble-free for at least five years or 13,000 hours.

Service life is 25,000 hours nominal with a 1.0 service factor, based on an AGMA standard. 25,000 hours is a nominal figure, so 50% won’t last that long. Use L10 life ratings, which means that 10% of the gearboxes operated at that load are expected to fail before the L10 life, and 90% are expected to last longer. So a gearbox with a nominal life of 25,000 hours would have an L10 life of 5,000 hours. According to AGMA guidelines, a conveyor not uniformly fed and operated more than 10 hours a day should have a 1.50 service factor. A similar calculation will need to be done for the motor.

Humidity
The most common system used to classify a product’s intrusion and water resistant compatibility is the IP rating, which is published by the International Electrotechnical Commission (IEC). (IP stands for International Protection, but is sometimes referred to as Ingress Protection.) Today, ac induction and permanent magnet ac motors typically meet protection classes IP54 or 55 and with certain steps can even satisfy IP65 or 67 demands. So the IP ratings do not properly provide protection for high humidity environments and other steps are necessary to protect the gearmotor. To prevent corrosion, protect all bare metal surfaces. Also, motor laminations should be painted. Use a continuous low voltage and current power supply to your winding to prevent condensation when the motor is not in use. For brakes, all wear surfaces must be stainless steel and sometimes a completely enclosed outdoor brake is the best solution.

Feedback and improvement
Life Cycle Cost analysis is a management tool that can help companies minimize waste and maximize energy efficiency for many types of systems. A complete understanding of everything that makes up the total cost of a system throughout its lifespan provides an opportunity to reduce energy, operational and maintenance costs.

Analyze each element of the life cycle and determine a realistic value for use in computing the total life cost, including purchase price; installation and commissioning cost (including training); energy costs; operation costs; maintenance and repair costs; downtime costs; environmental costs (disposal of contaminant liquids and contaminated used parts, such as seals); and decommissioning/disposal costs (including restoration of the local environment and auxiliary services.)

In addition to supporting a design decision, the LCC analysis can be used to reflect changes in scope, schedule or application. The process can become a valuable tool for continuous improvement.

ABM Drives, Inc.
www.abm-drives.com

New large contactors from Rockwell simplify motor control, improve energy efficiency

March 30, 2018 by Miles Budimir Leave a Comment

Global machine and equipment builders designing panels for global markets need to select the right components to meet numerous international standards as well as address changing energy-efficiency guidelines. To address these needs, Rockwell Automation has released the Allen-Bradley Bulletin 300 NEMA contactors and Bulletin 100-E IEC contactors to help machine builders design smaller, more energy-efficient panels.

Traditionally, contactors have been used to switch electrical loads in numerous applications, such as motors, fans and pumps. However, large size contactors are increasingly used in applications to isolate or bypass these loads and for switching of resistive loads. To accommodate this change, new lines of contactors feature a universal coil, which offers operators more flexibility when controlling with multiple voltages.

“Typically, with contactors, you need to specify what voltage you want to control with,” said Tom Peterson, global product marketing manager, NEMA Contactors, Rockwell Automation. “With the new lines, the contactors can be controlled with 40 to 50 different voltages, ranging from 24 to 500 V, with only four different coil options.”

Previous options were available in multiple voltages and often required an ac or dc coil to control applications. With the introduction of the universal coil, operators can more easily control voltage on multiple applications with fewer parts.

“These coils are also much more energy efficient,” said Peterson. “With the new device, operators can operate the same applications with a smaller power supply.”

In addition to the universal coil, the new contactors are significantly smaller than previous product lines. The Bulletin 100-E IEC contactors have a 25 percent smaller footprint while the Bulletin 300 NEMA contactors are 45 percent smaller than previous product lines.

The new contactors replace the Allen-Bradley Bulletin 100-D IEC and Bulletin 500 NEMA Size 6-8 contactors. While the previous line featured contactors for applications from 115 to 860 A, the new contactors are designed for applications from 116 to 2650 A.

Click here for more information.

www.rockwellautomation.com

Hysteresis loss and eddy current loss: What’s the difference?

March 30, 2018 by Danielle Collins Leave a Comment

All electric motors experience rotational losses during the conversion of electrical power to mechanical power. These losses are generally categorized as magnetic losses, mechanical losses, copper losses, brush losses, or stray losses, depending on the underlying cause and mechanism. Included in the category of magnetic losses are two types — hysteresis loss and eddy current loss.

Hysteresis loss

Hysteresis loss is caused by the magnetization and demagnetization of the core as current flows in the forward and reverse directions. As the magnetizing force (current) increases, the magnetic flux increases. But when the magnetizing force (current) is decreased, the magnetic flux doesn’t decrease at the same rate, but less gradually. Therefore, when the magnetizing force reaches zero, the flux density still has a positive value. In order for the flux density to reach zero, the magnetizing force must be applied in the negative direction.

The relationship between the magnetizing force, H, and the flux density, B, is shown on a hysteresis curve, or loop. The area of the hysteresis loop shows the energy required to complete a full cycle of magnetizing and de-magnetizing, and the area of the loop represents the energy lost during this process.

A hysteresis loop shows the relationship between the induced magnetic flux density (B) and the magnetizing force (H). It is often referred to as the B-H loop.
Image credit: NDT Resource Center

The equation for hysteresis loss is given as:

P_b = η * B_maxⁿ * f * V

P_b = hysteresis loss (W)

η = Steinmetz hysteresis coefficient, depending on material (J/m³)

B_max = maximum flux density (Wb/m²)

n = Steinmetz exponent, ranges from 1.5 to 2.5, depending on material

f = frequency of magnetic reversals per second (Hz)

V = volume of magnetic material (m³)

Eddy current losses

Eddy current losses are the result of Farady’s law, which states that, “Any change in the environment of a coil of wire will cause a voltage to be induced in the coil, regardless of how the magnetic change is produced.” Thus, when a motor core is rotated in a magnetic field, a voltage, or EMF, is induced in the coils. This induced EMF causes circulating currents to flow, referred to as eddy currents. The power loss caused by these currents is known as eddy current loss.

Motors armature cores use many, thin pieces of iron (referred to as “laminations”), rather than a single piece, because the resistance of individual pieces is higher than the resistance of one, solid piece. This higher resistance (due to smaller area per piece) reduces eddy currents, and in turn, eddy current losses. The laminations are insulated from each other with a lacquer coating to prevent the eddy currents from “jumping” from one lamination to another.

Eddy currents in laminated cores (right) are smaller than those in solid cores (left).
Image credit: wikipedia.org

The equation for eddy current loss is given as:

P_e= K_e * B_max² * f² * t²* V

P_e = eddy current loss (W)

K_e = eddy current constant

B = flux density (Wb/m²)

f = frequency of magnetic reversals per second (Hz)

t = material thickness (m)

V = volume (m³)

Magnetic losses are so named because they depend on the magnetic paths in the motor, but they are also referred to as “core losses” and “iron losses.”

Motion Trends: Customized solutions drive gearmotor development

March 27, 2018 by Miles Budimir Leave a Comment

The driving force in gearmotor design and development in large part is the desire for customized solutions, which consists in large part of simplifying integration into mechanical designs.

These trends are driving gearmotor manufacturers to offer their customers more simplicity. Along these lines, suppliers are offering their customers more in-house engineering resources to help them with their designs, which translates into more custom solutions.

Also as new applications arise, they call for design changes, such as in newer battery-powered designs. Case in point; engineers at Bodine Electric have been developing and testing gearmotors with optimized windings and motors for efficient operation at low voltages in outdoor and battery powered systems. Design enhancements include new winding configurations optimized for low resistance, and new magnetic configurations to optimize performance with the lower voltages available in battery powered designs.

This 3D-CAD model of Bodine Electric’s new PMDC planetary gearmotor shows the two stages of planetary gearing along with the O-rings on all the mating surfaces giving it an IP-66 rating.

Battery powered gearmotors and motors for mobile equipment and AGV applications are usually required to be as small and as efficient as possible. Designers of these mobile robots aim for the smallest possible motor footprint. Integrating sensors and actuator mechanisms with the gearmotor is a practical way of improving the use of available space.

The trend toward more custom designs also continues to impact gearmotor designs. “Many of our customers require custom electrical designs and mechanical features,” notes Mark Marhoefer, Director of Technical Research and Controls for Bodine Electric. “Typical customization of our gearmotors ranges from minor details like special tapped holes in the housings to custom magnetics, special castings, shafts, sensors, customized controllers and motor and control testing. We also conduct ongoing outdoors and environmental testing of these products to further validate out IP ratings.”

Others examples include adding custom castings to a gearmotor assembly that allowed an OEM to integrate their drive wheel mechanisms with the gearmotor, making the assembly and installation of the drive unit much easier and more compact. Bodine regularly incorporates custom feedback solutions within the motor design to allow the customer to easily interface the gearmotor with their electronics. These solutions include many types of temperature sensors, various shaft feedback devices for speed and position sensing and custom feedback designs for actuator arms with limited range of motion. Especially with the rising interest in the industrial IoT, companies are seeing an increasing the demand for sensor technologies at the motor. This typically includes increased demand for motor temperature sensors and sensors for velocity or position feedback.

Some examples of custom designed motors from Bodine Electric with integrated gearheads, wheel drive mechanisms and integrated sensors for automated warehousing applications.

Customization also includes more integration up front. For instance, motors with actuators designed for defined purposes such as lift actuators, rotating actuators and wheel drives. Also, gearmotors with integrated controllers allow the envelope to be more compact and eliminates the wiring typically required between the controller and the motor.

“Instead of selling a motor and letting the customer do the integration of actuator components for the application, we work with them to design a product that directly interface to the drive mechanisms,” explains Marhoefer. “This might involve integrating a pinion gear or actuator arm on our drive shaft with provisions to locate and mount the gearmotor. This will provide the correct fits and tolerances to allow the customer to bolt the gearmotor into their equipment and use it with minimal effort at the time of assembly.”

More integration also means gearmotor designs that are smaller and more compact. For instance, Bodine recently introduced an integrated planetary gearbox design that allows the gearmotor to produce twice the torque from a smaller diameter gearbox than comparable parallel shaft gearboxes. “Our customers benefit from the higher torque density and smaller overall gearmotor size, and the integral gearhead design eliminates the need for mounting flanges, couplings, and all related alignment challenges that come with separable gearhead assemblies,” adds Marhoefer.

Servo motor torque curves: What you need to know

March 20, 2018 by Danielle Collins Leave a Comment

A servo motor, when coupled with a feedback device, servo amplifier, and error-correcting control loops, can maintain a tightly controlled position, torque, or speed in applications that require closed-loop operation and the ability to respond to disturbances. But another benefit of servo motors is their ability to produce a significant servo motor torque curve over a wide range of speeds.

Accordingly, the servo motor torque curve, which depicts the amount of torque a motor can produce over its range of operating speeds, is one of the most useful tools in servo motor sizing and selection.

The servo motor torque curve shows two operating zones—continuous and intermittent. The continuous operating zone encompasses the combinations of torque and speed that the motor can produce indefinitely.

When evaluating whether an application lies within the continuous duty zone, the motor’s root mean square (RMS) torque is used. RMS torque takes into account the varying torque requirements during the motor’s full duty cycle—including acceleration, constant velocity, deceleration, and dwell—as well as the amount of time that each level of torque must be produced. The purpose of RMS torque is to determine the torque value that, if it was produced continuously by the motor, would result in the same level of motor heating as all the various torques and durations the motor experiences during its duty cycle.

Ambient temperature also affects how quickly the motor will reach its thermal limit, and therefore, its continuous torque rating. If the motor will be operated in an area with an ambient temperature greater than that specified by the manufacturer, the servo motor torque curve will need to be adjusted (de-rated) accordingly. Conversely, if the ambient temperature around the motor is well below the ambient temperature specified by the manufacturer, the motor’s continuous torque rating may be increased.

Servo motors have two operating zones: continuous duty and intermittent (peak) duty.
Image credit: Moog Animatics

Servo motor torque curves are relatively flat up to the motor’s maximum speed, unlike stepper motors, whose torque drops sharply beyond a certain operating speed.

The maximum torque required by the motor is typically the sum of torque during acceleration, torque due to the load, and torque to overcome friction. Because maximum torque is required for only a short amount of time, it can fall outside of the motor’s continuous operating zone, but must fall within the intermittent duty zone.

However, there are two caveats when considering the application’s maximum and its relationship to the motor’s intermittent operation zone: 1) the duration of maximum torque must fall within the time limit defined by the motor manufacturer for intermittent operation, and 2) both the maximum torque and maximum speed should fall within the intermittent zone (if either parameter lies outside the motor’s operating limits, damage to the motor could occur).

The maximum speed of the motor is limited by voltage, or more specifically, by back EMF voltage. Back EMF is generated by the motor’s rotation and opposes the applied voltage. As speed increases, so does back EMF, and at some point, the back EMF can reach or exceed the voltage supplied by the drive.

It’s important to note that the servo amplifier (aka servo drive) can limit the motor’s maximum operating parameters, so torque-speed curves are often developed for specific motor-amplifier combinations. Using a different amplifier than that specified for the torque-speed curve could change the motor’s continuous and intermittent operation limits.

Fortive selling Portescap, Kollmorgen, and Thomson to Altra Industrial Motion

March 9, 2018 by Lisa Eitel Leave a Comment

Fortive Corp. — a 2016 spinoff of Danaher — has agreed to combine four operating companies from its Automation & Specialty platform (A&S platform) with Altra Industrial Motion Corp. to form a global leader in the power transmission and motion control market.

The A&S business includes the market-leading brands of Kollmorgen, Thomson, Portescap, and Jacobs Vehicle Systems.

This A&S platform generated approximately $907 million in revenue for its fiscal year ended December 2017.

The $3.0 billion deal includes $1.4 billion in cash proceeds and debt reduction for Fortive and 35 million newly issued Altra common shares to Fortive’s shareholders — valued at $1.6 billion.

“We’re excited about this announcement, as it represents a major step forward in portfolio enhancement work towards increasing focus on software and service exposure, while adding significantly to our M&A capacity,” said James A. Lico, President and CEO of Fortive.

According to Lico, the combination represents value creation for Fortive and Altra shareholders, customers, and employees.

“We have great respect for the Altra team and their commitment to continuous improvement and customer satisfaction,” added Lico. “This combination of powerful brands and remarkable people creates an organization well-positioned to capture robust Industry 4.0 growth opportunities.”

“This transaction transforms Altra and represents a major milestone towards accelerating the acquisition strategy,” said Carl Christenson, Chairman and CEO of Altra. “The addition of the A&S platform bolsters our ability to compete effectively on a larger global scale in the broader automation space, to further our continuous improvement journey … and to optimize our portfolio in an expanded acquisition universe.”

The combination will be effected as a Reverse Morris Trust (and expected to be tax-efficient to Fortive). Fortive shareholders will get shares representing approximately 54.4% of the issued and outstanding shares of Altra after giving effect to the transaction and valued at approximately $1.6 billion. In addition, Fortive will directly receive added consideration of $1.4 billion through a combination of cash proceeds and debt reduction. Until closing (expected before the end of 2018) the A&S platform businesses will operate within the Industrial Technology segment of Fortive, and financial results will be reported in continuing operations.

Fortive will have the right to designate one member of Altra’s board of directors, expected to initially be Patrick J. Murphy — Senior V.P. of Fortive.

Fortive is a diversified industrial growth company comprised of Professional Instrumentation and Industrial Technologies businesses that are saw leaders in attractive markets. With 2017 revenues of $6.7 billion, Fortive’s well-known brands hold leading positions in field instrumentation, transportation, sensing, product realization, automation and specialty, and franchise distribution. Fortive is headquartered in Everett, Washington and employs a team of more than 26,000 research and development, manufacturing, sales, distribution, service and administrative employees in more than 50 countries around the world. With a culture rooted in continuous improvement, the core of the company’s operating model is the Fortive Business System. For more information, visit www.fortive.com.

New autoclavable BLDC motor controller from Portescap

March 5, 2018 by Lisa Eitel Leave a Comment

Portescap now sells an autoclavable Brushless DC motor controller — the CNT1530 — for driving large bone orthopedic handpiece motors. The controller leverages Portescap’s market leading autoclavable design capability and surgical application expertise to provide a reliable, customizable setup to the orthopedic market. This new controller will help improve surgical hand tool’s performance and reliability, and take application to market sooner.

The CNT1530 controller uses on-board hall effect sensors; the magnetic actuation of speed and direction provided by this design delivers exceptional reliability due to a lack of mechanical components. In addition, the electronic components are encapsulated in a silicone potting material within an aluminum housing, which provides protection of the circuit board from the harsh environments of sterilization washers and autoclaves. The controller is compatible with a range of input voltages allowing for use with multiple battery types. A small form factor enables designers to house the controller within a tool’s pistol grip to create exceptionally ergonomic designs.

The new BLDC controller is compatible with Portescap’s Large Bone Orthopedic motors. Customization is available for partners needing tailored setups.

Portescap offers the broadest miniature and specialty motor products in the industry, encompassing coreless brush DC, brushless DC, stepper can stack, gearheads, digital linear actuators, and disc magnet technologies. Portescap products have been serving diverse motion control needs in wide spectrum of medical and industrial applications – medical, life science, instrumentation, automation, aerospace and commercial applications, for more than 70 years.

Distributor insight: Conversation with Warren Osak on motion-control trends

March 2, 2018 by Lisa Eitel Leave a Comment

In a recent phone interview, we got to chat with Warren Osak, CEO of Toronto-based Electromate Inc. — a distributor founded in 1986 that focuses on electromechanical motion control. More specifically, Osak’s company sells primarily servo systems and stepper systems — often for demanding or challenging applications requiring high precision, accuracy, and bi-directional repeatability. Electromate also specializes applications destined for harsh environments and high duty cycles. Here’s what Osak had to say about current trends in the motion industry.

Lisa Eitel • Design World: One trend we see is an uptick in both traditional stepper-motor applications and those for hybrid steppers … especially in robots and medical applications.

Osak • Electromate: In the field of stepper motors, it’s a tale of two technologies. On one end of the spectrum, you have low-end steppers … and these can take the form of tin-can stepper motors (also known as can-stack stepper motors) that output rotary or linear motion. For the latter, the motor often incorporates an acme screw instead of an output shaft. Such technology is low cost and highly customizable — but there’s a lot of price pressure in this marketplace.

On the other end of the spectrum are integrated stepper motors. These have servo-like performance by closing the position loop around a feedback device such as an encoder. Plus, anti-resonance circuitry built into these stepper motors can ensure smooth acceleration between 50 and 500 Hz.

We see the middle of the market — actuated by the traditional 1.8° hybrid stepper motor as a standalone device — kind of going away. Technology is either migrating upward (and taking the form of integrated motors or smart motors) or migrating downward — to lower-cost motors with less sophisticated structures. More specifically, the use of traditional hybrid stepper motors has been yielding to integrated products … while in lower-end applications, we see more use of less-sophisticated motors with customer-provided integrated chips (ICs) to drive them.

Eitel: Battery-powered equipment is proliferating — especially in the form of ATVs, AGVs, drones, and service robots. What are the design challenges here?

Osak: For embedded robotic applications, we’re seeing a lot more 48-V and 24-V designs … and even some 12-V applications. Note that when I say embedded robotic, I’m talking about frameless motors — the brushless motors that run off low voltage and directly integrate into the wheel drives of AGVs, ATVs, and utility-task vehicles. In our marketplace, size requirements are increasingly challenging — with torque-density requirements also increasing … and that’s especially true for motion designs that run off low-voltage battery-operated systems.

Eitel: No conversation about trends is complete without some discussion of IIoT. What are your thoughts?

Osak: IoT has been a buzzword over the last few years, and we see a lot of IoT connectivity in the HMI and automation-control space … where HMIs connect on fieldbus networks to enterprise networks and other systems outside the motion design — including vision systems, supervisory control systems, and SCADA systems. All of these are increasingly interconnected — primarily through HMI devices with full IoT (Industrie 4.0) connectivity. But we’re not seeing a proliferation of IoT devices on the motion-control side of things — in motion controllers or programmable automation controllers, for example. I believe that adoption will come, but right now we’re not seeing it.

Today’s localized motion controllers or distributed controllers primarily handle I/O and not vast data processing and analysis … as they’re still task-specific motion-system components. In contrast, at the HMI level there’s much more networked manufacturing I/O.

Eitel: Do you see more OEMs wanting turnkey motion solutions?

Osak: There’s definitely continued push for more integration, and our customers often want to tie their machine controls into our motion control for a unified integrated solution — programmable under one language. That said, we don’t see individual component providers going away, as there will always be need for bespoke and best-of-breed manufacturers that build custom products for custom applications.

maxon precision motors EC 4 brushless dc motors (which can be fitted with GP 4 planetary gearheads) are 4 mm in diameter with an ironless winding.

Eitel: Anything you’re seeing in design miniaturization that impresses you?

Osak: There have been big advancements in the construction of servomotors. The physics of optimizing the magnetic flux generated from rare-earth magnet assemblies (and new production techniques) have leveraged improvements in motor designs. So, we’re seeing continued improvement in the torque density of servomotors well beyond what I once believed achievable.

In layman’s terms, the torque output one could get out of a NEMA-34-frame servomotor from eight or 10 years ago is now achievable with a NEMA-23-frame servomotor. In the same way, torque output of a NEMA 23 frame servomotor from eight to 10 years ago is now what today’s NEMA-17-frame motors can produce. So motors are definitively more power dense than in the past — and in fact for a given package size, there’s 50 to 100% increase in torque output versus motors produced a decade years ago.

What’s more, miniaturization is going to continue, because miniaturization imparts better use of space, reductions in mass, and reductions in cost — so I don’t see a point of diminishing return. Of course, there will be a point at which we get diminishing returns — where gains in servomotor construction simply don’t boost torque output appreciably — but we haven’t gotten there yet.

Eitel: Anything you’re seeing that’s prompting new uses for linear-motion technologies?

Osak: We’re seeing adoption of roller-screw actuation devices, which are more efficient than traditional forms of actuation (such linear bearing systems and round-rail bearing systems paired with ballscrew and acme screw drives). Increasing linear servo-actuator efficiency in turn allows design engineers to use more compact (yet higher thrust) actuators in applications traditionally driven by hydraulic actuation. In fact, electric linear actuators with roller-screw drive mechanisms can in some cases replace hydraulic drives even in very high-powered systems.

Eitel: Onto the topic of fluid power … what’s your take on servo-pneumatic designs?

Osak: We don’t sell any pneumatic systems, so I can’t comment on that directly … But I can say we get feedback from customers who want reliable solutions with longer mean time between failure (MTBF) — and a reduction in part count is a great way to get a higher MTBF. Because electrically driven servo actuators have fewer parts than pneumatic or hydraulic systems, they ultimately need (in theory at least) less downtime.

Eitel: Do you see any products that incorporate advanced materials to boost performance?

Osak: We see increased use of ceramics in gearing technology — with a few gearbox manufacturers now replacing case-hardened and steel and alloy gears with ceramic gears. We’re also seeing ceramic shafts and bits (such as pins) in gearboxes as well. Ceramic has a lot of unique properties — the most important being noise reduction. So in fact, planetary gearboxes with ceramic internals are half as noisy as traditional planetary gearheads … and they have a lower coefficient of heat expansion, so exhibit less stress than metal alloys when hot. Because ceramic components don’t expand as much, they also have tighter backlash and runout tolerances than comparable internals made of metal.

Eitel: This is news to me — because I primarily associate the use of advanced ceramics with rotary bearings.

Osak: Well, consider maxon precision motors. If I had to give a very rough guesstimate, I’d say 10% of all their gearbox products we see now have ceramic internals. They have a division that manufactures ceramic injection molding (CIM) and metal injection molding (MIM) gearbox internals for high-performance gearmotor designs. These include low-moisture gearboxes, low-backlash gearboxes, and high-torque gearboxes. Ceramic subcomponents definitely make sense in smaller-frame motors — especially those destined for medical applications where minimization of noise and vibration (and high load capacity) are critical.

Eitel: What technologies for motion control are currently showing the most innovation?

Osak: Sensor technologies seem to be advancing about twice as fast as other components used in motion-control systems. New developments for feedback devices also outnumber those for servo drives, rotary actuators, linear actuators, and motors — and I don’t know why that is. There’s certainly a lot of cutting-edge R&D in the world of feedback devices … so the pace of advancement in encoder, resolver, and linear variable differential transformer (LVDT) designs has just been astounding.

Eitel: We see electronics improving sensing and motion feedback.

Osak: Yes — and even with all this new technology, the price for feedback is coming down — it’s unbelievable. Just to give real-world example: Traditionally a design engineer would buy a motor and specify encoder resolution — and (whether incremental or absolute) encoder resolution was preset. But sometimes after that motor or servo actuator was deployed, you’d realize more (or less) resolution was needed. So what do you do? In the past, you had to buy another motor … or (in some rare cases) you could send the motor back, and the supplier would fit a different encoder.

Well today encoders can be field programmable. So you can buy an encoder … and if you think you need more resolution, you just program it (while it’s still in the field) with a handheld device. How cool is that? The ability to program an encoder for an application in the field in 30 seconds or less — without a pre-specified resolution — also means you can stock a supply of one given encoder model and just pull them off the shelf for programming as they’re needed. So design engineers have a lot more flexibility to standardize.

In fact, this is just the tip of the iceberg. Some encoders even include ASICs to allow more than just the programming of resolution. Some linear encoders even let end users program for pitch, N+1 feedback, and redundant feedback.

Eitel: Posital Fraba comes to mind here, as they sell very configurable encoders.

Osak: We sell Posital Fraba products, including encoders that have multiple tracks: One feedback signal is absolute, and one feedback signal is incremental, but they come from the same device. Each signal can be at a different frequency range and a different resolution. Electronics enable all this functionality and (in a lot of cases) field programmability. In short, this manufacturer listens to engineers and identifies their requirements … and then comes out with specialized product to meet those requirements. That differs from the “build it and they will come” motion-manufacturer mentality. So Posital Fraba manufactures more than a million encoder varieties — literally more than a million — and each is one customizable to each specific customer requirement.

Electric motors: Trends in stepper, battery-powered, and integrated motion designs

March 2, 2018 by Lisa Eitel Leave a Comment

From induction motors in electric vehicles to tiny coreless dc motors in drug-delivery equipment, electric motors continue to proliferate. Last year we saw consumer products, implantable medical devices, and automation of previously manual tasks spur the most innovation in motor design and use. This year those trends continue — and now we see increased use of servo and stepper motors in robotics.

maxon precision motors EC 4 brushless dc motors (which can be fitted with GP 4 planetary gearheads) are 4 mm in diameter with an ironless winding; ISO 13485 certified; and suitable for use in laboratory robots, micropumps, and diagnostic devices. Two lengths deliver power to 0.5 and 1 W. “We also want to offer more value-add services, as more companies than ever in the U.S. want finished motor and motion systems — so-called drop-in designs,” said McGrath of maxon. “So to that end, our expanding U.S. factory will have the capacity to supply custom assemblies and PCBs.”

In fact, whether it’s basic tin-can motors for low-cost custom actuation or integrated motors that output servo-like performance, overall use of stepper motors is growing. On the latter, a study by P&S Market Research projects a CAGR of 6.3% through 2023 for the global closed-loop stepper motor market. P&S cites the well-known benefits of control-feedback signals and power-adjusted current control as key reasons for the technology’s steady adoption.

Low-current dc motors from ISL Products Intl. Ltd. come in myriad mechanical and electrical configurations. Sometimes gearmotor modifications help the dc motors meet exacting OEM application specifications. In other cases, the motor must have special construction to avoid inducing EMI and RFI interference (Here, raw materials in the motor components are a main consideration, said to Kawaller of ISL.) Designs with reduced power consumption benefit from motors with specialized internal construction and nontraditional component materials.

Warren Osak, CEO of Toronto-based distributor Electromate Inc., sees this trend for integrated stepper motors, even while the middle of the stepper-motor market (actuated by standalone 1.8° hybrid stepper motors) recedes. Technology is either migrating upward (and taking the form of integrated motors or smart motors) or migrating downward — to lower-cost motors with less sophisticated structures, according to Osak.

“The use of traditional hybrid stepper motors has been yielding to integrated products … while in lower-end applications, we see more use of less-sophisticated motors with customer-provided integrated chips (ICs) to drive them,” he added.

Full interview with Osak: Motion-control trends distributor insight

Some closed-loop stepper manufacturers we surveyed for the Design World Trends issue include Schneider Electric Motion USA, Applied Motion Products Inc., Lin Engineering, MICROMO of Faulhaber, Oriental Motor Co., and Nippon Pulse America Inc. — with commentary from the latter in our actuator trends coverage. All detail pre-integrated or application-specific motor offerings. Case in point: Automation in the oil and gas industry has created numerous opportunities for motion control products, but stringent requirements for hazardous location ratings rule out most standard motor and drive solutions.

Use of tin-can stepper motors is on the rise, and now some new tools let engineers check their programming on the little motors more easily. Consider the Motion Checker 5 controller from Nippon Pulse America Inc. — a standalone handheld controller with an integrated driver circuit. Using it is as simple as plugging it into a normal outlet and connecting a stepper motor to run through motion sequences.

“To serve engineers in this industry, we’ve released the world’s only ATEX-rated stepper drive for hazardous locations … and this year we’ll introduce our first explosion-proof step motor to pair with it,” said Eric Rice of Applied Motion Products. “The drive is already being used on rigs in the oil field for applications where accurate braking and speed control of drill strings are required.”

Motors in (proliferating) battery-powered designs

Battery-powered designs such as ATVs, mobile robotics (including AGVs), scooters, ebikes, and drones present unique motion-system challenges. Motors that integrate into these designs might need to accept 48, 24, or 12-V input, and nearly all of them must meet tough efficiency requirements … NEXT PAGE →