HM Series Hybrid Stepper Motors from Portescap

Portescap’s new HM series hybrid stepper motors are available in 42mm and 57mm frame sizes with short stack, one stack and two stack design in each frame size. Windings can be customized to satisfy specific application requirements at no extra cost. HM series motors include optional encoder mounting features, and their ability to adapt to closed-loop control systems helps eliminate the need for customization. Depending on the stack length, HM 42 size motors provide holding torque up to 65 oz-in and HM57 size motors up to 330 oz-in. 

HM series hybrid stepper motors, as drop-in replacements in most industrial and medical hybrid applications, allow machine builders to reduce the ownership cost of their machine with no noticeable sacrifice in performance.  As a result, these RoHS-compliant hybrid step motors are an ideal solution in life sciences, fluid handling, industrial automation equipment, medical devices and vending/ticketing applications.

For more information, email sales.america@portescap.com or visit www.portescap.com.

Stepper motors

One of the most common motors used in motion control applications is the stepper motor. These motors are used mostly in positioning applications and have the advantage of being able to be very accurately controlled for the most precise positioning applications, down to fractions of a degree without the use of feedback devices such as encoders or resolvers. They are operated in open-loop (not closed-loop), without the need for tuning parameters as in closed-loop servo systems.

Steppers are generally classified by the number of allowable steps they can be commanded to move. For instance, a 1.8 degree step motor is capable of 200 steps/revolution (1.8 x 200 = 360 degrees, or one full revolution) in full-step mode. If operated in half-step mode, each step becomes 0.9 degrees and the motor can then turn 400 steps/revolution. Another mode called microstepping subdivides the degrees per step even further, allowing for extremely precise movements.

There are several different stepper motor technologies including permanent magnet motors, variable reluctance, and hybrid types. The principle of operation for stepper motors is fairly straightforward. Traditional variable reluctance stepper motors have a large number of electromagnets arranged around a central gear-shaped piece of iron. When any individual electromagnet is energized, the geared iron tooth closest to that electromagnet will align with it. This makes them slightly offset from the next electromagnet so when it is turned on and the other switched off, the gear moves slightly to realign. This continues with the energizing and de-energizing of individual electromagnets, thus creating the individual steps of motion.

Hybrid stepper motors are more expensive than permanent magnet stepper motors but provide better performance with respect to step resolution, torque and speed. Hybrid steppers combine the best features of both the permanent magnet and variable reluctance type stepper motors. The rotor is multi-toothed like the variable reluctance motor and contains an axially magnetized concentric magnet around its shaft. The teeth on the rotor provide a path to help guide the magnetic flux to preferred locations in the airgap. This further increases the detent, holding and dynamic torque characteristics of the motor when compared with both the variable reluctance and permanent magnet motor.

Stepper motors are relatively inexpensive and can be run open loop, requiring no feedback devices. Also, because the speed is proportional to the frequency of the input pulses, a wide range of speeds is attainable. However, while stepper motors are capable of producing high torque at low speeds, they generally are well suited for lower power applications not for applications requiring lots of torque to move heavier loads. They are best for applications requiring the control of rotation angle, speed, and position.

A few drawbacks are that not properly controlling the motor can produce undesired resonance in the system. Also, stepper motors are generally not easy to operate at extremely high speeds. And as the motor speed increases, torque decreases.

For two-phase stepper motors, there are two basic kinds of winding structures; unipolor and bipolar. A unipolar arrangement uses 6 wires but current can only flow in one direction. These types of motors also require a unipolar driver. A bipolar winding uses 4 wires and current can flow in 2 directions and it requires a bipolar drive. Bipolar motors are generally more efficient and can provide more torque than unipolar models, although they can heat up faster than unipolar motors.

A stepper motor’s low-speed torque varies directly with current. How quickly the torque falls off at higher speeds depends on a number of factors such as the winding inductance and drive circuitry including the drive voltage. Steppers are generally sized according to torque curves, which are typically specified by the manufacturer.

Stepper Motors from Nippon Pulse for High Torque Applications

Radford, Va. – For high torque applications in a variety of industries, Nippon Pulse offers the PF55 stepper motor, a two-phase tin-can style brushless motor available with both unipolar and bipolar windings. 

With a unipolar winding, the PF55 stepper offers a holding torque of 120N, while a bipolar winding provides 150N of holding torque. In a full-step (2-2) excitation mode, the PF55 has 48 steps per revolution, a rated voltage of 5 and 12V, inductance between 12 and 37mH, and resistance between 5 and 36 ohms.

The PF55 stepper motor also comes in a gearhead model with 20 different ratio options, ranging from 6/25 to 1/300. These gearhead motors provide maximum torques of 400, 700, and 1000mN·m. All variations of the PF55 motor are also available with a connector.

Nippon Pulse PF55 motors are ideally suited for liquid dispensing devices, valve control machines, torque metrology instruments, printing machines, and medical diagnostic systems.

For more information, visit www.nipponpulse.com

www.nipponpulse.com

35mm Linear Stepper Motor from Nippon Pulse

Radford, Va. – Nippon Pulse’s PFL35T LINEARSTEP® tin-can type linear actuator gives engineers the ability to design a linear motion system simply and at a low cost. Nippon Pulse’s LINEARSTEP series offers direct linear motion without the need for any mechanical transformers, allowing users the ability to design a simple system at a low cost. 

The PFL35T features an outer diameter of 35mm and features neodymium magnets, which allow for a high driving force. Its sturdy design and construction and its ball bearing support makes the PFL35T durable and gives it a long life cycle.

The PFL35T is available with three lead screw pitches (0.48mm, 0.96mm, and 1.2mm), both bipolar and unipolar windings, a force rating up to 39.5N (at 200pps), rated voltages of 5V and 12V, and 48 steps per revolution.

Applications for the PFL35T include XY stages, liquid dispensing devices, medical pumps, semiconductor wafer handling machines, and data storage recorders.

For more information, visit www.nipponpulse.com.

PF25G gearhead stepper motor delivers high torque in compact package

Nippon Pulse (www.nipponpulse.com) has unveiled its latest PFG25G gearhead stepper motor.

Coming from the company’s well-established portfolio of tin-can stepper products, PFG25G gearhead stepper motor is suitable for medical device industry’s projects that demand for high torque motor but have limited space.

The gearhead stepper motor is offered both in unipolar and bipolar winding and features 24 steps or 48 steps per revolution. Depending on the device’s step number and winding, Nippon’s gearhead stepper motor offers a rated voltage of either five volts or 12 volts. It also delivers a resistance ranging from 15 ohms and 122 ohms, a holding torque that stands between 8 mNom and 12 mNom. Weighting 35 grams, the PFG25G stepper motor’s other remarkable features include a starting pulse of 490 pps or 790 pps, a maximum torque of 100 mNom and a motor diameter of 25 mm.

Nippon’s PFG25G stepper motor offers customers the choice of more than 20 gearhead ratios, starting from 6/25 to 1/300. Depending on the motor’s gear ratio, it produces a maximum torque of between 20 mNom and 100 mNom.

Just like the rest of Nippon Pulse stepper motor products, the company offers customers the option to customize their PFG25G motor to meet their individual need. The Nippon Pulse factory and model shop can add longer lead wires, connectors, ball bearings, customized flanges, pinions and many other motor options.

Borries integrates high-speed drives in its markers

Borries Marking Systems (www.borries.com) has announced the release of the latest high-speed motor drives integrated in its programmable dot peen and scribe marking machines. These drives replace the more complex and expensive servo drive systems, which are current alternative for marking situations.

Borries latest markers feature an upgraded, high-speed stepper motor drive system that reduces cycle time in half-or more.

The drives were originally developed in response to the demands of the automotive industry for lower machine cycle times but faster production rates, as manifested by automotive stamping plants, where the stamping plants deliver 12 characters in three seconds at a speed of 5 mm.

Aside from the new systems, which are capable of increasing the throughput and reducing the cycle time, the company also provides retrofit packages for existing devices.

With the use of higher speed drives, the devices can be installed as retrofit kits either at the Borries factory or in the field. This gives users an affordable solution for optimizing marking speeds without the need of acquiring a new device.

Borries’ high-speed drives can be translated into several marking technologies: Stylus Marking, which utilizes fast-vibrating needle technology to produce minimal force on three-dimensional material; Scribe Marking, which is ideal in almost all deformable, three-dimensional configuration and delivers continuous-line mark that are easily-readable; Dot Matrix Marking, which is similar to Stylus Marking and Scribe Marking, but provides a visible dotted appearance; and DataMatrix Marking, which uses the same tool with the dot matrix and provides 2D codes (ECC 200 standard) that are camera-legible.

These high-speed drives are offered in the company’s programmable dot peen and scribe machines portfolio.

Rohm introduces high-performance stepper motor drivers

Rohm Semiconductor (www.rohm.com) is proud to announce the release of its new high-reliability, high-performance stepper motor drivers that offer selectable excitation modes, full-step to 16th-step with 1 A or 2.0 A output current and full-step to 8th-step with 2.5 A output current. The stepper motor drivers are now available in RS Components stocks (www.rs-components.com).

The microstep drivers allow designers to optimize vibration, noise and motor torque for a broad range of applications. The circuit design is simplified by combining the features of an internal voltage regulator, DMOS output and control input translator. Operating from a maximum single 36 V supply, Rohm advanced DMOS (Pch + Nch) output topology does away with the need for external charge pump components.

The stepper motor drivers incorporate over-voltage, thermal protection and under-voltage not typically integrated in motor driver ICs. The drivers’ packaging benefits include a bottom-side heat sinking to simplify thermal design, pin-compatibility within parts with different current ratings, as well as adjacent-pin short protection on most of the models to reduce field and production failures, said the company.

B&R Expands Line of Synchronous and Stepper Motors

B&R Industrial Automation announces the addition of precision planetary gears to its line of synchronous and stepper motors. The result is a high performance and economical drive program for all industrial fields that can be optimized to meet customers’ needs and is provided from a single supplier. Together with the renowned German manufacturer Neugart, B&R developed a motor-gear building block principle that is otherwise not available on the market.

The planetary gears are delivered fully mounted on B&R’s 8LSA, 8LVA, 8JSA and 80MP series motors. Troublesome communication problems between the motor supplier and gear supplier are now a thing of the past. Gears in both straight and angled designs and with all conventional drive flange geometries were developed together with Neugart as technology partner.

The standard gears are single-stage for gear ratios i=3, 4, 5, 8 and 10 and have ≤ 8 – 15 arcmin backlash. The gears are also offered in two-stage or three-stage designs. At the top of the product line, the premium series provides backlash ≤ 1 arcmin as an option paired with high output torques.

B&R Industrial Automation
www.br-automation.com

Micromech introduces TMCM-078 stepper motor drive module

Micromech (www.micromech.co.uk) is pleased to launch its TMCM-078 stepper motor drive module with coil currents up to 7A and 75V.

The TMCM-078 stepper motor drive is made for bipolar two-phase stepper motors, operating with motor coil currents of 0.7A to 7A (rms) (9.8A peak) and voltages of 15V to a maximum of 75V.

Depending upon the application, a high RPM of up to 256 micro steps or a high accuracy is possible, according to the press release.

A sensor-less load measurement capability can detect mechanical blocking, thus it can substitute reference switches plus the needed wiring.

The inputs for the direction, step and enable signals are optically isolated. The motor current is reduced to an adjustable level in standstills (standby) to prevent the motor from heating up unnecessarily, as well as to prevent the waste of energy.

All the outputs and inputs can be linked with JST crimp connectors or screw-pluggable connectors.

The module is available in rugged aluminum housing measuring 145mm x 96mm x 33mm.

TI introduces new DRV8412 evaluation kit

Texas Instruments Incorporated (www.ti.com) is pleased to introduce its all-new DRV8412 evaluation kit (DRV8412-C2-KIT) – a new line of scalable evaluation platforms intended for spinning motors. The kit includes all of the software and hardware needed to spin a single stepper motor or two brushed DC motors out of the box. It also speeds up development time for stepper and brushed DC motors running up to 6A continuous/12A peak at 50V. Applications include gate openers, medical pumps, textile manufacturing tools, stage lighting, and consumer or industrial robotics.

Among the kit’s features are out-of-the-box motor control and driver solution, which includes motors, the DRV8412-C2-KIT, a quick-start GUI, full development source code, Code Composer Studio (CCStudio) fitted with development environment (IDE), and a real-time control C2000 Piccolo microcontroller (MCU) controlCARD module. Modular control architecture provides flexibility to choose the suitable level of processing performance for the application. Additional TI MCU options will also be available next year.

The DRV8412 motor with integrated MOSFETs offers up to three times lower Rdson than other solutions, allowing up to 97% efficient operation, and delivers 6A continuous/12A peak current at 50V, eliminating the need for a costly heat sink. The motor driver also incorporates advanced on-chip protection such as under-voltage protection, over-temperature, and cycle-by-cycle over-current, to reduce design board space and complexity and ensure higher system reliability.

C2000 Piccolo MCU can perform communications, debug and control. The 32-bit C2000 MCU incorporates the most advanced CPU capability and control peripherals in an embedded MCU device family. This includes open-tooled reference designs through free controlSUITE software, real-time debug capabilities and access to the most systematic set of motor control software modules.

Easy-to-use GUI and C source code demonstrate current and voltage control of one or two brushed DC motors, as well as index and speed, which include up to 128 microsteps, of a stepper motor.

JVL launches world’s shortest stepper motor

Danish motor specialist JVL (www.jvl.dk) is proud to launch an integrated stepper motor – which it says is the world’s shortest stepper motor with a built-in controller. The 3-Nm version of the motor is only 95 mm long, but incorporates all the stepper control electronics, such as a programmable motion controller and IP67-protected CANopen and RS-485 interfaces.

The stepper motors offer a resolution of 819,200 steps/rev for smooth and quiet operation. The motors integrate everything needed for stand-alone control or operation from a PC or PLC. A total of eight I/O points can be configured as digital inputs/outputs, or analogue inputs. Aside from the 95 mm-long version, there is also a 126 mm version that can deliver 6.1 Nm, as well as a 156 mm version that delivers 9 Nm.

The stepper motors are said to deliver an acceleration precision of 1rpm/s and a velocity precision of 0.01rpm. The motors operate from 12V DC to 80V DC supplies and can deliver high torque at high speeds.

An ActiveX/OCX driver is also supplied to simplify interfacing with Excel, VB, LabView or other PC-based programs. Use of MAC protocol from JVL allows SMC85 controllers and QuickStep and MAC motors to be integrated on the RS-485 bus, supporting multiaxis or point-to-point operation of up to 254 axes.

Options include planetary gears, RS-485 and RS-422 interfaces for encoder I/O and connection to external PLCs or HMIs, double-shaft and single- or multi-turn encoders, and a pulse/direction mode for electronic gearing. The stepper motor can be available with wireless WLAN, Bluetooth or ZigBee functions, and is ready for next-generation options such as industrial Ethernet, Profibus and multi-turn encoders without external batteries.

Prior Scientific introduces LF210 system: stepper motor focus control

Prior Scientific (www.prior.com) is proud to announce the release of its all-new LF210 Laser Auto Focus system that is intended for use with a wide variety of reflective samples including hard disc drive platens and semi-conductor wafers. Developed from the Industry Standard LF100, this new LF210 integrates a number of refinements resulting in a more stable and sensitive machine unit. This means that the system can be used to maintain focus on a broader range of specimens. An integrated modulated laser diode helps the LF210 to be one of the most stable Laser Focus Unit available on the market.

The new LF210 Laser Auto Focus system can control stepper motor focus drive or piezo focusing devices like Prior Scientific’s NanoScan. Line or Spot laser modes are now designed as user selectable. This means that one unit can be utilized for all types of sample irrespective of the number of features present.

The LF210 is ideal for use on upright microscopes with infinity corrected optics. A range of mounting flanges is also available to suit specific microscopes.

The LF210 also features a fast auto-focusing for reflective samples, piezo focus control from 0V to 10V output, LF100K keypad for stand alone operations, and stepper motor focus control.

Encoder Options for All Angles of Stepping Motors

Oriental Motor announces that encoder options are now available for their 0.36° and 0.72° stepping motors. With the addition of the encoder option to 0.36º and 0.72º stepping motors, Oriental Motor’s entire range of stepping motors (including 0.9 º and 1.8º stepping motors) now has the option for an encoder. Additionally, the stepping motors are available as a stepping motor only or as a stepping motor and driver package.

The new stepping motor encoder options for 0.36º and 0.72º motors are:

• 500 or 1000 pulses/rev
• 2 or 3 channel
• TTL or Differential (line driver type)

For 0.36° and 0.72° stepping motor and driver packages, Oriental Motor has introduced the CRK stepping motor and driver package. The CRK stepping motor and driver package highlights include:

• Pulse input 24 volt driver
→ 500 or 1000 pulses/rev
→ 2 or 3-channel TTL type encoders

• Built-in controller type
→ 500 or 1000 pulses/rev
→ 3-channel differential line driver type encoders

Oriental Motor
www.orientalmotor.com

Toshiba Electronics introduces motor driver ICs for arcade games, card readers

Toshiba Electronics Europe (www.toshiba-components.com) is proud to announce the release of its two high-voltage, high current motor driver ICs, which are designed to simplify stepper motor-based designs in various industrial and office automation applications.

The TB62215FNG and TB62213FNG, based on a PWM constant current drive scheme, are single-chip two-phase bipolar stepper motor drivers that can deliver maximum motor output currents of 3.0A per phase and maximum motor output voltages of 40V.

The TB62215FNG operates with a clock-in decoder for clock input control, while the TB62213FNG has a control interface that makes use of phase input information provided by a host microcontroller.

Each driver has an on-chip voltage regulator to help create complete stepper motor control designs with the use of a single-motor power supply of as high as 40V.

Further flexibility in the design results from its capability to select two-phase, W1-2-phase, or 1-2-phase excitation modes.

A power-on-reset (POR) function and on-board thermal over-current shutdown help in minimizing component count and board space.

Manufactured through the company’s  BiCD process, the TB62215FNG and TB62213FNG incorporate DMOS FETs as output power transistors.

Supplied in 48-pin HTSSOP packages, the motor driver ICs will be ideal to applications ranging from vending machines and office automation equipment to arcade games and card readers.

Servo2Go.com Expands Line of Integrated Step Motors

Greenville, DE- Servo2Go.com has expanded it’s line of Integrated Step Motors to include many new NEMA 17 frame models.

Manufactured by Applied Motion Products, the STM is a Drive + Motor + Control unit, fusing step motor and drive technologies into a single device, offering savings on space, wiring and cost over conventional motor and drive solutions.

Communication options include: RS232, RS485, CANopen, Ethernet and Ethernet/IP. Models are CE marked, and RoHS Compliant.

Servo2Go.com

Stepper motors power Open Date’s thermal transfer printer

UK-based Open Date Equipment (www.opendate.co.uk) is proud to announce the release of its Thermocode iQ thermal transfer printer.

“The iQ has advantages in both print accuracy and reduced operating costs compared with other machines, while maintaining the speed and precision associated with more expensive models. It is designed to operate with all intermittent labeling and packaging machinery,” said Gary Cowlard, chief executive of Open Date.

“The high specification iQ uses no compressed air to operate the print head, which is electronically driven by three stepper motors. These motors can be very accurately controlled, which in turn allows more print cycles per minute (currently up to 800) as well as better quality and consistency.”

“When developing this state-of-the-art thermal printer we took into consideration both the performance and sustainability criteria demanded by end users. With no need for compressed air the printer is a major step forward for this technology addresses both these key requirements. In addition the gentler handling of the motor means the life expectancy of a print head is twice that of air operated printers. Running costs are also significantly reduced and maintenance intervals are longer than for traditional machines.”

The Thermocode runs at a total speed of 600mm/s with a maximum print area of 53mm x 110mm. It is controlled by a 7″ touchscreen on which stored printed images can be edited and print settings can be adjusted during use. Program updates and print images can be downloaded through a USB port, which can be used as back-up memory. On-board memory stands at 8mb.

With its accurate ribbon drive system, 1,000 meter ribbon capacity and its ability to make fine manual adjustments, the Thermocode provides maximum efficiency of ribbon usage that further reduces operating costs and wastes.

High Torque Hybrid Stepper Motors from Applied Motion Products

Greenville, Del. – Servo2Go announces a new NEMA 24 frame series of high torque hybrid stepper motors. Manufactured by Applied Motion Products (AMP), the HT24 motors are a new frame size stepper motor offering up to 30% more torque than the previous HT23 series in a similar package size. The only significant difference in size between an HT23 and HT24 is that the HT24 has a larger shaft diameter. The HT24 motors mount within the same mounting pattern as the NEMA 23 frame motor family.

HT24 motors are ideal for applications where more power is required but changing to a size 34 motor is not possible. HT24 motors are available with single or dual shafts, have four leads and are suitable for bipolar and unipolar connections, and are optimized for microstepping. Three different stack lengths with holding torques ranging from 123 to 354 oz-in are available. Optional encoders, gearheads and brakes are also available.

Specifically wound for low inductance and low rated per phase current, the HT24 motors are ideally suited to run with AMP’s low cost STR4 microstepping drive.

For more information on HT24 Stepper Motors, visit http://www.servo2go.com/product.php?ID=105285

www.servo2go.com

B&R Automation’s new stepper motors

B&R Automation (www.br-automation.com) is proud to introduce the new 80MPF series stepper motors with 60mm flanges described as cost-effective and powerful. The 80MPF series stepper motors, with 30% less power loss and 25% more torque, are ideal for applications with high clock rates such as filling systems or packaging machines.

The 60mm 80MPF, 86mm 80MPH and 56mm 80MPD motors are known to be one of the most powerful stepper motors available in the market with regard to holding torque. The company now offers motors for demanding applications with holding torque ratings between 1.1Nm and 13.6Nm.

To control the motors, B&R offers Acoposmicro, X67 system and X20 system stepper motor modules that handle currents between 1A and 10A.

Special attention was paid when designing the 80MPF series to ensure that the installation flange is matched with the current 56mm motors from the 80MPD series. Thus, the two motors series’ mounting holes are identical. Just like all B&R motors, the new robust stepper motors also have a long operating life thanks to the high-quality materials.

The company carefully made the right selection for stepper motor bearings since these are major elements when it comes to reliability in harsh conditions.  Moreover, the seals on the bearings offer protection from moisture and contamination.

The 80MPF series motors have IP30 as standard, but IP65 protection can be achieved with the optional cover. The 60mm motors can be equipped with an ABR encoder, a motor brake and/or an SSI encoder depending on the application requirements.

Super Torque 5818 Stepper Motor Series from Lin Engineering

Lin Engineering announces the release of the new Super Torque 5818 stepper motor series. Although these motors measure in at a mere 2.40”, they boast up to 305 oz-in of holding torque.

The 5818 stepper motor series is a slightly larger version of Lin Engineering’s popular 5718 step motor line. Although they share the same mounting as the 5718 motor series, the new Super Torque 5818 stepper motor provides up to 50% more torque due to its slightly larger body. Bipolar and unipolar windings are available with the added option of getting a custom winding for high speeds or low resonance at no extra cost.

Common industries that may benefit from the added torque of a 5818 stepper motor are: packaging, automation, printing, semiconductor, dispensing, and many more. Custom options such as shaft modifications, cabling & wire harnesses, pulleys, and high temp materials are also available.

Lin Engineering
www.linengineering.com

The Many Faces of Stepper Motor Drives

Drives for stepper motors continue to advance beyond the basic L/R type drives.

A typical linear motion control system has several basic components, including motors, actuators, controllers and drives. The drive type plays an important role in the overall system. Here’s a look at the most basic drive configurations, including the latest advancements in chopper drives.

The IDEA programmable actuator from Haydon Kerk is an example of cutting-edge intelligent chopper drive technology. IDEA consists of an advanced microstepping chopper drive with an intelligent programmable controller mounted to the rear section of a hybrid stepper motor linear actuator in one fully integrated package.

Defining the L/R Type Drive
An L/R type drive is a voltage source drive, where the L refers to electrical inductance and R stands for electrical resistance. Inductance is an electrical parameter relating mainly to inductors that are coils of wire wrapped around a core material that can be metallic, non-metallic, solid, liquid, or even air. Typical inductors are transformers, chokes, and motor coils (including the windings in stepper motors and stepper motor linear actuators). A related parameter called inductive reactance in an electrical circuit impedes the flow of current relative to the voltage frequency. It can be thought of as a “dynamic resistance,” increasing and impeding more of the current flow as the frequency increases. An analogy for inductance in the mechanical field would be the principle of inertia.

Resistance also impedes the flow of current in an electrical circuit but is a constant value and is not affected by the frequency value of the voltage or current. The stepper motor coil resistance remains essentially the same from standstill through maximum step frequency with only minor fluctuations due to temperature. A mechanical equivalent of electrical resistance would be the friction in a system.

Stepper motor manufacturers offer a variety of coil voltage ratings. With an L/R type of drive, you set the output voltage of the drive (measured at the motor leads) equal to the voltage rating of the stepper motor. The voltage level of the drive power supply will be set slightly higher due to voltage drops across the power transistors. The ratio of inductance to resistance (L/R) determines the current flow through the windings at a given step rate (or frequency) in steps per second. L/R = 1 time constant, which is equal to approximately 63% of the final steady-state current. At standstill, the maximum current flow into the windings is determined by the coil resistance alone. The impedance effect due to inductance is zero when the frequency is zero. This is the condition where the motor has maximum torque (holding torque) due to maximum ampere-turns, defined by:

T_H α N x I

Where:

T_H = the holding torque
N = the number of turns in the motor coil
I = the electrical current

As the step rate increases, the coil inductive reactance (X_L) also increases according to the formula:
X_L = 2πfL

Where:
X_L = the inductive reactance
f = the frequency (step rate)
L = the inductance of the motor coil

With a constant voltage source L/R type driver, the motor current decreases as the total impedance (X_L + R) increases.

Because torque, both static and dynamic, depends on ampere-turns, the output performance of the stepper motor or stepper motor linear actuator drops off as the speed increases. Another factor affecting motor performance is the back-EMF (electro-motive force) produced by the rotor rotating in a magnetic field. Motors also behave as generators. High step rates may produce peak back-EMF levels approaching or exceeding the L/R drive output voltage level. One method used to partially compensate for these effects is to improve the inductance to resistance (L/R) ratio by adding external series resistors and increasing the power supply voltage. Some common configurations are the L/2R and the L/4R drivers. Because the respective voltage sources would have to be doubled or quadrupled, the efficiency drops significantly and much more of the power is wasted as heat in the external resistors.

Categories of L/R Drives: Unipolar and Bipolar
Unipolar drives have simple output configurations and are used infrequently due to the relatively low torque output and low efficiency. A unipolar drive contributes to a torque reduction of approximately 30% as compared to a bipolar drive at the same electrical power. In a unipolar drive, only half the phase winding is energized at one time, whereas in a bipolar drive, the entire phase winding is energized.

A unipolar drive configuration. Notice that the motor phase winding is center-tapped, thus allowing current to flow through only half the phase winding at a time.

A bipolar drive configuration.

Bipolar drives have more complex output stages. Many of the new specialized integrated circuits have come down in cost, making bipolar drives more affordable. The output configuration is an “H-Bridge” which allows the reversal of the phase currents. Instead of the phase currents being switched on and off in just half of the windings like in a unipolar configuration, the currents flowing through the entire motor windings are reversed in bipolar drives. At equal electrical power into a given frame size stepper motor, the bipolar driver/motor configuration can produce greater static and dynamic torque than that of a unipolar driver/motor combination.

Chopper Drives
The term chopper refers to the method of rapidly switching a relatively high voltage to the windings on and off. This technique of switching the output voltage on and off controls the average current per phase.

There are several steps involved in selecting a chopper drive. First, choose a power supply that has a high output voltage relative to the voltage rating of the stepper motor to be driven. The high available voltage compensates for the increasing coil impedance due to rising inductive reactance as the motor speed increases. A power supply to motor coil voltage ratio of 8:1 or higher will provide the best performance at the higher motor speeds. Second, low-voltage steppers, with correspondingly lower inductance coils, are recommended. Linear type motor power supplies work well with these drives. Third, virtually all chopper-type drivers are a bipolar configuration, making use of the entire motor windings, which yields improved torque. Even unipolar stepper motors can be driven with these bipolar choppers as long as their rated coil voltage is not too high. Six-lead unipolar motors would be connected as a four-lead type by leaving the center-tap leads unconnected. With eight-lead steppers, you can connect the two coils of each phase in series (especially low-voltage coils) or in parallel. Because inductance changes as the square of the number of turns, putting two coils in series yields four times the inductance. Stepper motor performance improves at the higher speeds, as compared to an L/R type drive, due to the chopper drive’s method of monitoring and controlling motor current throughout the usable speed range.

To control the average current through the phase windings, this type of drive technology “chops” the high output voltage on and off. Most choppers use a fixed chopping frequency of approximately 20 kHz or higher. This helps keep system noise low, since the chopping frequency is above audible range. Based on this constant fixed chopping frequency, the average output current is controlled by varying the pulse width of these repetitive output pulses, a technique known as pulse width modulation (PWM).

The output current is monitored by comparing the voltage level across a small ohmic value series sense resistor with a set voltage that represents the rated motor current. During each cycle of the typical 20-kHz waveform, the voltage across the sense resistor begins to rise as the current increases through the motor winding. An electronic comparator continuously monitors this voltage level; when it equals the set reference voltage it turns off the output voltage until the start of the next 20-kHz cycle. The current in each motor winding builds and decays as the voltage source switches on and off during each cycle, yielding the proper average current per phase.

As the motor step rate, or speed, increases or decreases, so does the corresponding winding impedance and the chopper drive electronics help to compensate for this effect. At slow speeds (lower winding impedance) the on time of the voltage source is relatively short per cycle (small pulse width). At higher speeds (higher winding impedance) the on time is longer per cycle to allow the current to increase to the proper level (large pulse width); thus the term pulse width modulation.

Advances in Chopper Drives
Chopper drives are now selected for most new stepper motor linear actuator applications and there has been ongoing progress in this drive technology. For instance, the use of low on-resistance Field Effect Transistors (FETs) in the output power stage increases system efficiency and reduces power dissipation within the drive, which also reduces the required heatsink area and physical size of the drive package. Also, new power stage circuitry can provide the higher phase currents required from low-voltage, low-inductance motors, which can yield improved performance over a wider speed range. Enhanced phase current control increases motor performance such as automatically providing boosted current levels during acceleration and deceleration ramping, or shaping to reduce overall resonance of the system.

Other advances include multiple levels of microstepping (electronically splitting a full step into smaller increments) to increase motor resolution, reduce motor resonance, and lower the motor’s audible sound level during operation. Also, the integration of smart controllers, by use of on-board microprocessors, which allows for execution of real-time motion functions such as indexing with or without ramping, and creating complete interactive motion profile programs. These programs can be downloaded into non-volatile memory on the controller and then run independently and un-tethered from any host computer.

In the realm of I/O, interactive optically isolated inputs and outputs now allow the driver/controller to fully communicate with other devices and equipment in a motion control system. And smart controllers can accept encoder feedback, which can be used for motor positional verification or speed control.

Discuss this on the Engineering Exchange:

Haydon Kerk Motion Solutions
www.haydonkerk.com

::Design World::

Fully Integrated Stepper Motor/Driver from Johnson Electric

Vandalia, Oh. – Johnson Electric introduces the Saia Compact Driver, a fully integrated step driver/motor solution that reduces design and integration time, and improves device performance compared with traditional stepper solutions by virtue of reduced parts count and greater immunity to electromagnetic interference.   Where space and power is at a premium, the Compact Driver’s low power consumption and small footprint make it a particularly attractive motion solution for battery powered portable devices.

The Compact Driver provides 3-wire operation of 28mm Saia motors, including UCL and UCE linear step motors and UCD and UCB rotary stepper motors. The linear Compact Driver solution provides forces from 0.1 to 50N with a step resolution down to 0.021mm and distances up to 150mm. The rotary Compact Driver solution can be combined with an Saia UGA, UGD or UGM gearbox to obtain higher torque and RPM outputs, and increase step resolution, all from the same integrated driver board.

The Compact Driver’s algorithm is programmed to detect the end of the motor’s stroke. This automated end stop detection eliminates noise, reduces mechanical stress, and compensates for transverse distance tolerances, helping decrease system hysteresis and maximizing operating life.

Additionally, the Compact Driver is available with three different types of control interfaces that can be used for any number of applications where on/off or proportional functions are desired, making it simple to integrate into new and existing device designs. The ON/OFF mode is operated by an external switch where the proportional function is controlled by a 0-10V or pulse width modulation (PMW) signal.

For more information, contact Johnson Electric at (937) 454-2345 or by fax at (937) 898-8624.

www.saia-motor-usa.com

High-speed MODBUS with Integrated Servo Motors from JVL

JVL Industri Elektronik A/S now offers yet another feature: The latest firmware for the integrated servo motors MAC400 and MAC800 now supports the MODBUS RTU protocol.

The implementation supports the Read Holding Registers and Write Multiple Registers commands, which will give R/W access to all motor registers at speeds up to 1 Mbit/s, though typically the PC standard rates of 9600..115200 and 230400 bits/s would be used.

The implementation uses the original V1.1 version of the MODBUS protocol for maximum compatibility. For systems requiring a 2-wire RS-485, the MAC00-P4 interface module is used. For 4-wire RS-422, the MAC00-FSx modules or one of the MAC00-Bx modules are used.

MODBUS is generally considered the most widely used serial communications protocol in the industry.

JVL International
www.jvlusa.com

High-Performance Hybrid Stepper Motors from AMETEK

Kent, Oh. – AMETEK Technical and Industrial Products’ new MAE^® brand Size 34 (Model HS 200) hybrid stepper motors exhibit superior torque characteristics to power a wide range of industrial equipment applications. Their low detent torque to holding torque ratios deliver smooth and quiet operation and the fine positioning capability required for microstepping.

Their top-to-bottom insulation system incorporating stator insulators and other components enables the steppers to withstand internal temperatures up to 130ºC. Robust design and rugged construction contribute to reliability and long service life.

These hybrid steppers include three versions with step resolutions of 1.8º (200 steps per rev) in full-step mode. Holding torques (bipolar) of 779 oz-in, 1062 oz-in, or 1416 oz-in can be achieved, depending on motor type. All are available in standard NEMA34 mounting configuration.

Other features include precision-honed stators and ground rotors for tight air gap and maximum performance, single- or double-ended shaft extensions, and high-temperature grade neodymium iron bore magnets. Motors can be supplied with 4 leads and single- or double-ended shafts upon request and can additionally be customized with gearboxes, encoders, and other options to satisfy particular application specifications.

Typical applications for these steppers include actuators, packaging machinery, pumps, and other equipment across industries. The motors are CE approved and manufactured according to EN 60034-1 specifications. UL versions are available upon request.

www.ametektechnicalproducts.com

Saia® UAL series Linear Stepper Motors from Johnson Electric

VANDALIA, OH – Johnson Electric introduces Saia® UAL series Linear Stepper Motors. These motors deliver constant positioning force up to 30 N over the full travel distance of up to 15 mm, at speeds up to 4.16 mm/s at 200 Hz. They feature a unique removable bayonet-style flange for easy mounting, a flexible design that easily accommodates various custom requirements, and a compact 20 x 30 mm footprint to deliver advanced performance in space restricted applications.

Saia UAL series motors are available in unipolar or bipolar models, with performance attributes that make them well suited for use in instrumentation, valve control, dispensing, metering pump, auger and medical automation applications.

Johnson Electric
www.saia-motor-usa.com

Powerful Stepper Motors from B&R Automation

B&R is expanding its range of products to include additional high-performance standard devices for the automation industry – with five new 86 mm flange stepper motors (NEMA 34) that have holding torque values ranging from 4.0 to 13.6 Nm. The design and control enables high-precision and cost-effective positioning without an encoder system. The 80MPH series stepper motors with an 86 mm flange as well as the 56 mm 80MPD series motors are among the most powerful motors currently available on the market in regard to holding torque and length.

With the 80MPH series and 80MPD series, B&R offers the most powerful and efficient stepper motors on the market.

Equipped with an aluminum housing, the new NEMA 34 motors are able to transport thermal power dissipation with the lowest possible thermal resistance. This considerably reduces heating of the motor, which increases the lifespan of the bearings. As critical components, B&R places great value on adherence to the highest quality standards when selecting the ball bearings. The close-fitting seals not only protect against oil loss, they also generally prevent dirt particles from penetrating, which ensures that the lubricant is working at full efficiency. This even prevents oil loss when operating at high speeds. The optional IP65 upgrade with built-in clamp for the back of the motor makes wiring easier and permits use in particularly harsh environmental conditions.

The outstanding dimensioning of the components enables the motors to handle high longitudinal and transverse forces. The stepper motors can be delivered with or without an encoder system. The mechanical robustness of the magnetic encoders ensures trouble-free operation in industrial applications and therefore offers customers maximum reliability.

B&R Automation
www.br-automation.com

Lin Engineering’s New 4518 NEMA 17 Stepper Motors

Santa Clara, CA — Lin Engineering are pleased to introduce the new 4518 NEMA 17 stepper motors. The 4518 series, designed exclusively with Lin Engineering’s patent pending Signature Series technology, is the new and improved version of the 4118 motors delivering both super torque and smooth motion.

The 4518 series is available in three different stack lengths starting with the nimble 4518S at 1.34” in thickness and the powerful 4518L measuring in at 1.89”. Depending on the stack length, these motors are capable of producing up to 83 oz-in of holding torque. As an added value, Lin Engineering is able to customize the motor performance and create new windings at no extra cost; various bipoloar and unipolar windings are available based on the needs of the application. Additionally, Lin Engineering is able to offer a number of mechanical customizations such as shafts and wiring harnesses.

The new 4518 series is suggested in applications where size is a factor and load capacities are critical to precision system operation. Industries currently benefiting from the features of this motor in their applications are: medical, printing, imaging, optical, and robotics.

Signature Series Technology:
Lin Engineering’s new patent pending Signature Series technology is now available with the 4518 motor series. The Signature Series was developed exclusively to help reduce system resonance and provide overall smooth motion. Depending on the application, using motors with the Signature Series technology may result in up to 50% less resonance being produced.

www.linengineering.com

Portescap’s h3 Stepper Motors

WEST CHESTER, PA – Portescap offers a stator-enhanced version of its h3 Series Step Motors. New h3 models feature patented enhancing magnets in the stator to provide 25+% more torque output across the entire speed range compared with original h3 models, which already deliver up to 40% more torque than traditional hybrid step motors.

With its industry-leading efficiency and performance, the h3 allows machine builders to reduce the size and weight of their machine by utilizing a smaller motor to deliver the same performance of larger hybrid steppers. This further allows machine builders to use smaller drives, which reduces power requirements and overall system costs. Machine builders using the same size h3 as a standard hybrid will realize increased machine throughput. As a result, these RoHS-compliant hybrid step motors are an ideal solution in medical device, semiconductor equipment and laboratory instrumentation applications.

These 1.8-degree step motors feature aluminum housing for superior heat dissipation, Neodymium iron boron magnets for optimized torque density, and a bearing retainer and o-ring to help reduce motor noise. Larger bearings enable the motor to effectively handle higher side and radial loads. They are available in NEMA 17, 23 and 34 frame sizes, with various stack lengths available in each frame size. Windings can be customized to suit individual application needs.

www.portescap.com