Electric drives improved in density, efficiency and reliability

“Motorettes” implemented to study the effects of high voltage gradients on the voltage distribution among windings

RAISE European Project, coordinated by the group of Electrical Machines and Drives – MeltingLab of University of Modena and Reggio Emilia (UniMoRe), aims at offering solutions to improve the reliability of power converters, of machines and of the entire electric drive, without damaging their performance and efficiency. Benefits and ameliorations that are likely to exert positive repercussions in both the short and the long term, besides being exploited by manufacturers to face the competitive Asian market.

In recent years, the need of implementing increasingly powerful, light and efficient electric and electronic devices has become a priority target in all industrial sectors. For this reason, the release on the market of new wide bandgap based power devices, made of silicon carbide (SiC) and gallium nitride (GaN) semiconductor materials, has aroused lively interest in scientific and industrial communities.

Time trend of power devices’ power densities

Automotive and aerospace industries rank among those that can most benefit from these devices.
In this context, according to recent development trends focused on “More Electric Vehicle” (MEV) and “More Electric Aircraft” (MEA), the replacement of hydraulic/mechanical actuators with electric drives implies a neat improvement of efficiency and power density, which means also weight reduction, minor fuel consumption and lower emissions of noise and polluting substances.

The added-value of wide bandgap based power devices

The converters based on wide bandgap power devices feature superior characteristics than conventional devices based on silicon (Si). Such devices offer faster switchovers, minor power losses and they can operate at higher voltages and temperatures than their silicon counterparts, so allowing also a further reduction of volume and weight in converters’ cooling system.

Simplified scheme of an electric converter-cable-motor system. — Simplified scheme of an electric converter-cable-motor system

«It is then clear – explains Dr Stefano Nuzzo, member of the research team of UniMore, University of Modena and Reggio Emilia, “Electrical Converters, Machines and Drives”, together with Professor Davide Barater, Professor Giovanni Franceschini and Mr Marco Pastura – that the new devices based on SiC and GaN semiconductors materials perfectly match the above-mentioned targets».

However, the electric stress combined with the high voltage gradients they can reach, in addition to the combined action of other environmental stresses (like temperature, pressure and humidity) can shorten the life time of the insulation system of electric motors powered by converters that use SiC and GaN semiconductors.
Therefore, reliability problems can emerge in this type of electric drives. Moreover, the physical length of the power supply cables that connect the power converter to the motor can be comparable, or even exceed, the so-called “critical length”. «In this case – Dr Nuzzo underlines– the high rising and falling voltage pulses make cables behave like transmission lines, with waves that travel forward and backward along cables themselves due to the reflection phenomenon. These high-frequency phenomena can cause dangerous overvoltages at motor terminals, up to twice the direct-current bus voltage, the worst case, which can seriously damage the electric insulation of motor windings».

Prototype of the SiC converter used, with possibility of setting different levels of voltage gradients.

In particular, if the values of the dielectric rigidity of insulations are exceeded because of voltage levels at electric motor terminals, conductive phenomena through a portion of the insulation material occur, leading to the so-called partial discharge phenomenon. Partial discharges occur on the surface of the electric insulation, causing a progressive erosion up to the complete breakdown. The critical length is proportional to the switchover time, therefore the very short switching times of SiC and GaN devices have made the cable use problematic even for an extension of few metres. Besides, electric power transmission networks currently proposed for aircrafts are addressing the use of higher and higher voltage levels on bus in direct current, to minimize conduction losses.

However, the voltage rise on bus in direct current causes a further stress on the stator winding insulation, thus worsening the issues connected with the use of wide bandgap based devices.

From the state-of-the-art to the progress beyond it

The project RAISE – “Reliable Aircraft electrical Insulation sElection” is framed in this context. The project, started in March 2018, is funded by Clean Sky consortium, the primary research programme on European scale, included in Horizon 2020 funding system, which aims at the development of innovative solutions for the reduction of CO₂, of greenhouse gases and of the acoustic pollution. The group of Electrical Machines and Drives – MeltingLab of University of Modena and Reggio Emilia (UniMoRe), led by Professor Giovanni Franceschini, is coordinator of RAISE project and Professor Davide Barater is its Principal Investigator. Other two members of the MeltingLab assist their work in the project: Dr Stefano Nuzzo himself and Mr Marco Pastura. «MeltingLab – Dr Nuzzo specifies – collaborates with the main groups of the Department of Engineering “Enzo Ferrari”, of which it too is part, and cooperates with the most renowned area companies operating in the sectors of automotive, electric drives, industrial electronics and electrical machines».

Complete experimental bench: converter-cable-motor

In the last years, the group’s research has focused on electric mobility, mainly working on the design of electric drives for the control of high-performance electric motors through advanced prototypes of power converters with SiC modules, and on the design of electric machines featuring high efficiency and reliability.
Considering all criticalities previously highlighted, it is worth first of all assessing whether the insulating materials currently in use in electrical machines and in electronic power devices are suitable for applications that exploit higher and higher power supply voltages and switching gradients, such as in the case of the wide bandgap based semiconductors previously mentioned. Therefore, the first phase of RAISE project was committed to the analysis of the state-ofthe-art and to the experimental evaluation of insulation materials and systems used in in current aerospace applications. Afterwards, to better understand the impact of high voltage gradients, they have developed some models to quantitatively assess the values observed in a typical system composed by power converter, cable and electric machine, considering the typical operating conditions of the aerospace environment and the dependence on the alternating voltage (three-phase at 115 Vrms versus 230 Vrms).

Typical voltage distribution in the windings of an electric machine

The limit for the direct-current bus voltage was fixed at 1 kV, while the maximum voltage gradient considered is 20 kV/µs. Nevertheless, for these studies, they have considered also higher voltage and gradient levels, which might be reached in the next future. «These models – Dr Nuzzo specifies– can assess also the voltage distribution inside the windings of the electric machine and its dependence on the key parameters of the machine».

RAISE PROJECT (RELIABLE AIRCRAFT ELECTRICAL INSULATION SYSTEM SELECTION)

RAISE (Reliable aircraft electrical insulation system selection) is a 30-month project, receiving funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme. The consortium brings together two of the most prestigious Italian Universities: University of Modena and Reggio
(UniMoRe) and University of Bologna (UniBo). UniMore leads the consortium as project coordinator whereas the company LiebherrAerospace, multinational operating in the aerospace sector, acts as Topic Manager for the project. RAISE aims at investigating and assessing partial discharges and breakdowns of electric insulation in electrical machines’ windings driven by wide bandgap converters of silicon carbide (SiC) and gallium nitride (GaN). Goal of the project is offering solutions to improve the reliability of power converters, of machines and of the whole electric drive, without damaging performance and efficiency. Consequently, the aircraft of the future, besides being “more electric”, will be more reliable, more compact and lighter, and fuel consumptions and the environmental impact, mainly measured on CO₂ emissions, will be drastically reduced. It will be possible to transfer conceptually and practically the results of the project to the automotive industry, where the same electrification trend is taking place.

To demonstrate the validity and the accuracy of these models and to customize simulation parameters, they have built some “motorettes” representing senting a typical stator slot, suitably wound. Afterwards, they have also built some samples of electric motors, on which they have carried out some specific experimental tests. The experimental bench represents a typical converter-cable-motor system, with which it is possible to set up different levels of direct-current bus voltage and of voltage gradients, eventually exceeding, where required, the maximum pre-established of 20 kV/µs.

Innovative methodologies to reduce high voltage gradients

The project subjected to in-depth study is also aimed at verifying when the partial discharge phenomenon on insulation systems starts. «In this second phase, – Dr Nuzzo highlights – we developed some models based on the estimation of components’ life time and we carried out some experimental tests aimed at studying the impact of the voltage variation speed on partial discharges.

Research team of UniMore, MeltingLab of University of Modena and Reggio Emilia, “Electrical Converters, Machines and Drives”, (from the left): Professor Giovanni Franceschini, Mr Marco Pastura, Professor Barater, Dr Stefano Nuzzo

The investigation was executed considering also the variations of environmental conditions in terms of temperature, humidity and pressure».
The final goal consists in making the developed models represent some guidelines for the detail design of components “free” from partial discharges, through the estimation of the service life of insulation systems. The capability of designing insulation systems free from partial discharges will allow then granting the reliability of all the components of the electric system at stake and consequently of the entire aircraft.

AUTO-MEA PROJECT (AUTOmated Manufactoring of wound components for next generation Electrical Machines)

The final project phase, whose activities will be performed during 2020 and will go on until the end of the project planned by October 2020, will consist in the study and in the development of innovative methodologies for the reduction of the high voltage gradients iat the machine input terminals, without damaging the demanded efficiency and power density requirements.The results of this project – Dr Nuzzo specifies– will allow using power converters based on wide bandgap SiC and GaN semiconductor materials on board of aircrafts. Such converters will be characterized by high power densities and, as direct consequence, we will achieve a substantial reduction of the weight of the aircraft itself, of the fuel consumption and of its environmental impact». The outcomes of the project itself will be used by designers of motors and electric drives to test solutions and to adopt precautions before the implementation of physical prototypes.Since November 2019, UniMoRe has been also the coordinator of the European project AUTO-MEA (AUTOmated Manufacturing of wound components for next generation Electrical machines). The target of the initiative, included in Clean Sky 2 European Research Programme, is the development of new methodologies for the manufacturing of wound components of electric motors to be used in the aerospace field. AUTO-MEA consortium, in addition to UniMoRe, is composed by CopperING srl, reference company in the production of manufacturing lines for electrical machines’ stators in automotive fi ld, and by the University of Nottingham, which acts also as project Topic Manager. The replacement of pneumatic and hydraulic actuators with electric drives standing out for compactness and reliability represents one of the most promising trends nowadays but it needs innovative solutions for the design of electrical machines. AUTO-MEA will focus on the typology of preformed “hairpin” windings that, even providing numerous advantages compared to “random” windings at low frequencies (such as higher reliability and power density), reduce electrical machines’ efficiency at high frequencies. The project is aimed at pushing the boundaries of hairpin windings’ operational frequencies. The results by AUTO-MEA will have relevant repercussions also in other sectors, especially in the automotive industry where the Emilia territory is protagonist on a world scale.

This will improve the reliability of the electric drive and of the whole aircraft, which has always been one of the limiting factors in MEA context. «We expect – Dr Nuzzo concludes– such improvements will exert positive repercussions in both the short and long term and they can be exploited by European electric drive manufacturers to face the Asian market and then to be more competitive on a world scale».
(by Gianandrea Mazzola)

The vibro-acoustic analysis in electric motors

Editorial Staff

The vibro-acoustic analysis is fundamental in the sizing of any mechanical component. Not only because vibrations produce both mechanical and noise effects but also because the mechanical motion can generate stress and/or undesired dynamic behaviour of the system. Besides, the induced stress is correlated to fatigue and can cause premature breakages of the device. The fatigue failure depends on the number of cycles: even if the stress level is by far inferior to the maximum tensile stress of the component, at the end a failure can occur. With the rise of the power density of electric motors and more ad more demanding specifications, the vibration forecast in the initial design phase has then become a very important matter. An operational ambit where is protagonist Spin Applicazioni Magnetiche, service company working in the sector of electromechanical device design and distribution of simulation programmes for electromagnetic devices, electric motors, mechanical analysis and control systems. «In many industrial applications – Alessandro Tassi, CEO of Spin Applicazioni Magnetiche, explains – low vibration/noise levels are demanded: from the automotive industry to household appliances, from the diversified HVAC to the variegated power tools. The comfort of end users is as fundamental as the failure prevention».

The added-value of the multi-disciplinary analysis

Forefront Finite Element calculation instruments (Fem) allow an assessment of the behaviour of an electromechanical device since the first design stages, avoiding corrective actions when it is difficult to modify already advanced design choices, unless with cost increases and with an extension of the product time to market. Spin Applicazioni Magnetiche holds the expertise to guide accurate multi-disciplinary analyses on such theme.

Spin Torque-power performances — Torque-power performances of the motor for automotive

«From the electromagnetic context of the Fem calculation – Tassi underlines – we extrapolate the electromagnetic forcings and, through a dedicated connection, we evaluate, in the mechanical context of finite elements, the iterations with the mechanical structure equipped with the motor, allowing the determination of the real displacement of all parts, and eventually analysing noise radiation aspects». The company can boast multi-year experience in such applications, both through dedicated consulting in home-appliance field and in automotive sector.

Electromagnetic and vibrational FEA analysis

As confirmed by the numerous assignments entrusted for the management of entire projects, from the initial design to the implementation of very performing prototypes, where the vibro-acoustic analysis has been the key element of the project.

High power density at the service of automotive

The development of a traction motor for sports cars is an example of the above- mentioned workflow. Spin Applicazioni Magnetiche, from simple inputs of power (120 kW) and speed (30,000 rpm) and maximum footprint, has guided the customer to the implementation of prototypes. «The motor design –Tassi further explains – started from the typical white sheet, with electromagnetic and mechanical optimization as elements that have guided the device development since the beginning. The electromagnetic forcings calculated have become the input for mechanical analyses; the motor structure has been optimized to reduce vibrations, stator and rotor laminations, magnets, the frame and the shields were subjected to a single vibro-acoustic optimization».

In comparison with the first hypothesized design of the automotive motor featuring 120 kW of power and 30,000 rpm, the team of Spin Applicazioni Magnetiche has succeeded in notably reducing acceleration peaks

Such approach has allowed notably reducing some acceleration peaks, up to 94% versus the first hypothesized design, the thermal analysis has concluded the design course, providing this brushless motor with remarkable performances in a volume slightly under three litres. «Through this calculation method –Tassi confirms – prototypes were validated and, without turning to design modifications, we could immediately proceed to the implementation of samples for the approvals needed for the mass production. All that with notable decrease of design times and costs».

High efficiency and low noise at the service of the home appliance

The same multi-disciplinary operational methodology was applied in another successful case, for the testing of household appliance motors for which, besides efficiency, also the noise becomes a key issue that makes the difference in the product. «The electromagnetic and mechanical model of a high-speed motor for household appliances –Tassi highlights – has given excellent results of correlation with experimental measurements, too, allowing the customer to understand how to act in the reduction of accelerations in determinate harmonics that generated resonance phenomena with the entire application where the motor itself was mounted».

VIBRATION, THIS (UN)KNOWN

The vibration term specifically refers to a mechanical oscillation around a point of balance. The oscillation can be periodical, like the motion of a pendulum, or random, like the motion of a tire on an asphalt road; the frequency measurement unit for periodical oscillations is the Hertz that corresponds to how many times, in a second, the same configuration occurs again.

In many cases, vibrations can represent a wished phenomenon: for instance, in the operation of the diapason and of many musical instruments. However, more often vibrations are not welcome as they can disperse energy and create unwanted sounds and noises. For instance, in the running of cars and motors in general. The studies concerning the sound and the various vibrations are strictly connected. Sounds, pressure waves, are generated by vibrating structures (for instance vocal cords) and pressure waves can generate structure vibration. Therefore, when we try to decrease noise, the issue is reducing the vibration that causes it.

This has permitted to act on the source of the problem, to optimize it and to avoid a long empiric approach to find scarcely flexible and expensive stopgap solutions. It is perfectly clear how the vibro-acoustic multi-disciplinary simulation approach must become a standard workflow for each designer of rotating electrical machines, so avoiding unpleasant surprises during prototype tests. «Spin Applicazioni Magnetiche –Tassi ends – can support its customers both through the supply of specific software and through targeted know-how supported by a long-term experience gained by our skilled team on such fundamental theme».

Alessandro Tassi, CEO Spin Applicazioni Magnetiche

THE COMPANY IN BRIEF

Spin Applicazioni Magnetiche is a service company operating in the design of electromechanical devices and the distribution of simulation programmes for electromagnetic devices, electric motors, mechanical analysis and control systems. It pays particular attention to users’ requirements via software customization, creation of prototypes and magnetic measurements.
Spin Applicazioni Magnetiche is also distributor of highly professional calculation software, benchmark in the simulation field for many engineering disciplines, i.e. a very broad range of available programmes that cover all design aspects. The decennial knowhow gained in electromagnetic simulation is completed by expertise in structural mechanical analysis, multi-body, thermal analysis, fluiddynamics (Cfd), mechatronics and all that is typically included in the multiphysics design sphere. In addition,
Spin Applicazioni Magnetiche is also enabled to the training and use of calculation programmes; it supplies technical- scientific consulting, support in the development of new designs and it can take care of complete projects from the initial idea to the production of prototypes and manufacturing technologies.

(By Gianandrea Mazzola)

Comau introduces a new 4.0 seaming system for electric vehicles

Editorial Staff

Comau, pioneer in the development of advanced laser welding processes and applications, has created highly specialized laser laboratories to support companies in the development, implementation and optimization of laser processes that concern the manufacturing and the assembling of electric motors and batteries.
With two laboratories at Grugliasco (Turin) – one specialized in batteries and the other dedicated to e-motors, besides other laboratories in Shanghai and Detroit, Comau has all-round strengthened its value chain in the electric sector with the offer of a broad range of laser processes for various industrial sectors, such as automotive, aerospace, General Industry, energy and Oil & Gas.
In this way, Comau aims at increasing the efficiency, the speed and the value of companies’ productions, allowing them to offer highly competitive solutions in the electrification field.
For this reason, its specialized laser laboratories have been equipped with Comau NJ-220 robots, able to work simultaneously and on different kinds of applications, powered by the innovative LHYTE (Laser Hybrid Technology) system, developed by Comau in collaboration with Prima Electro.
LHYTE is suitable for numerous different applications due to a patented solution that allows automatically alternating fibre and diode laser to guarantee an optimal high-precision junction, fundamental for assembling an electric battery or an electric motor.
Moreover, LHYTE can manage the complexity of working materials, such as copper and aluminium, characterized by different melting temperatures, meanwhile assuring a strong joint tightness with a low level of electrical resistance.
“We can make any type of battery pack with whatever power level, besides, we can assemble the entire electrical battery, from the welding of the single cells that make up a module to the stacking of the various modules that constitute a battery pack, up to the laser welding of the entire “case” – explains Giovanni Di Stefano, Chief Technology Officer – Electrification of Comau. “In our brand-new laboratory we are also developing a similar solution for the laser welding of hairpin motors”.
Comau laser laboratories can be configured, equipped and adapted according to the demanded working process and to the type of product under manufacturing.
Besides satisfying a broad range of applications, Comau develops and optimizes each phase of the laser welding process, from prototyping to the production of pre-series, when requested by customers.
Each project is supported by a dedicated team of engineers, who develop and identify the best welding solution for each customer, with services that range from feasibility studies to the process optimization.

The innovation of printed circuit board stator motor

Redazione

The innovation promised by Infinitum Electric, Texan start-up, concerns the stator. It is implemented in printed circuit board on plastic support instead of with conventional iron. In this solution, the copper circuit is integrated in a single printed circuit board, to reduce the energy dispersions associated to the core, thus proving to be 60% lighter, up to 10% more efficient, more compact and even 25% cheaper than a standard electric motor. Moreover, the electric unit can reduce the torque ripple, minimizing noise while used, can integrate drives in the motor and install all sensors in the printed circuit board stator.

These novelties are expected to make the motor sturdier and more durable because the stator, which contains the entire coil, can boast a thermal expansion coefficient that remains homogeneous in all points. Technologies are protected by 5 patents already registered and other 11 under certification; recently, Infinitum Electric has accomplished the funding of 12.5 million dollars to produce the new motor on a world scale.

Magnetization process for PM rotors

Luca Melideo

The Permanent Magnet (PM) motor is a critical part in many electric car powertrain designs, which is undergoing rigorous improvement and changes. PM motors offer compact design and higher system efficiency among other advantages.

The race for the electric cars has begun in the automotive industry and companies are vying for an edge in this market segment. The Permanent Magnet (PM) motor is a critical part in many electric car powertrain designs, which is undergoing rigorous improvement and changes. PM motors offer compact design and higher system efficiency among other advantages.

Electric motor Engineering magazine asked Laboratorio Elettrofisico, a global company that specializes in design and manufacturing of high-quality magnetizing and measurement equipment, to illustrate how to deal with this important process.
In recent years, Laboratorio Elettrofisico (LE) has made great strides in the research, development and implementation of in-situ magnetization for PM rotors in powertrain applications.

MAGNET ARRANGEMENTS

Tab. 1 – Hsat expressed in kA/m is the magnetic field required to fully saturate a magnet from its unmagnetized, green state. For convenience, it has been expressed in terms of Flux Density, B[T]

LE offers solutions based on not only the electro-magnetic analysis, but on a complete multi-physics analysis, that includes thermal and stress analysis, pertaining to the in-situ magnetization. Finally, customers are offered custom design solutions, specific to their needs. In most cases, magnetizing systems will typically consist of a dedicated magnetizer along with a custom build magnetizing fixture and associated measurement and automation devices.
The magnetizer is a standalone pulse power supply unit for magnetizing fixtures. It mainly consists of a power capacitor along with its charge and discharge unit. In addition, it contains sophisticated signal processing and other software controllers, managed via HMI-TS display with remote control capability. Beside local remote control, an intercontinental connection is also available for remote service. Tailor made magnetizers feed energy to the magnetizing fixtures, necessary for magnetizing PM devices. Depending upon the electrical conductivity of both magnet materials and surrounding assembly parts, either low capacitance, high voltage configuration or vice versa, high capacitance and low voltage combination may be needed for proper magnetization avoiding eddy current effects. LE latest series of iMag magnetizers caters to all such needs.

Structural dynamic simulation on a bench frame (Displacements scaled up)

PM rotors come in many different shapes and sizes due to many contributing factors. The magnet position is one such contributing factor. PM rotors can have magnets in V-shape, spoke shaped or they can be surface mounted, among other shapes. Each magnet arrangement necessitates a unique magnetizing fixture with an optimal design besides being durable as well as tailored for mass production.
Magnetizing fixture design is affected by a multitude of factors such as number of poles in the rotor, rotor skew, height of a rotor, magnet material, space availability, customer specific requirements such as particular field along a specified path or surface, etc. Additionally, with growing system complexity, the market requirements are evolving, and, in some cases, customers request to not only saturate the magnets, but also knock them down after magnetization to a desired level of saturation.

PEOPLE AND SKILLS

Laboratorio Elettrofisico is a global company specializing in the engineering, design, and manufacture of magnetizing and magnetic measuring equipment. Founded in 1959, the company is headquartered in the Nerviano area of Milan, Italy. In addition to design and manufacturing operations in Italy, LE has laboratories, testing facilities, support staff, and services centers in the United States and China.

Design phase overview

Pulse field magnetization is evaluated using FEA software. Target of this design phase is to simulate the field required for saturating the rotor magnets. Depending on the market needs, field produced on an external surface or path, harmonics, etc. may also be evaluated and used as control parameters. Fixture design starts with electromagnetic FE simulations. Subsequently, thermal behavior and cooling requirements are evaluated, in thermal design phase. Lastly, stress analysis is performed to understand the forces acting on the rotor. These can be exported and provided to the customers if required, to aid in their own mechanical design, or to LE engineering department for the automation design. The above-mentioned design phases are sometimes performed parallelly instead of sequentially to create a feedback loop for complex design cases.

The main tasks of a magnetization bench are to position the magnet correctly during the pulse magnetization process. It also has to withstand large forces generated during the pulse magnetization and the forces generated by the magnets on overall bench post magnetization. These forces can be significantly higher in case of rotor-fixture angular misalignment or if the rotor is not positioned correctly during magnetization. Using electromagnetic FE simulation these forces are evaluated and exported to run a stress analysis on the entire bench, while considering safety factors higher than three or four times Von-Mises stress limit.

Overview of 3D FE simulation in fixture design. 1D optimization approach may be used when high number of geometrical and physical parameters are involved 8. 3D FE thermal simulation on a magnetizing fixture

Design impact of pole number

For a two-pole rotor a uniform magnetizing field is needed along half the circumference, while on the other hand, for a 30 poles rotor, a sharp magnetization between poles must be obtained. This is successfully done by optimizing the slots design for optimal conductor placement. FEA software and optimization tools are used to adjust parameters such as the slot depth, slot opening etc.

Design impact of rotor skew and height

Typical dimensions of a powertrain rotor height can range up to a few hundreds of mm. Axial distributions of magnets in rotor can be straight, skewed, step skewed. There are two ways to manage magnetization of such long rotors.

Magnetize the rotor stack by stack with axial steps. This process is usually slow and needs as many numbers of magnetizing shots as the number of stacks in the rotor assembly. This is quite versatile as using the same magnetizing fixture heads, rotors with varying skew patterns and rotor height can be easily magnetized.
Second method of handling large rotors is to use a single shot magnetization, where the magnetizing fixture is usually taller than the rotor, this process is more energy efficient and only one shot is required, but it is dedicated to one model. If you change the skew angle or the rotor height you would need a different fixture.

Design impact of magnetic material

Magnets used in PM motors can be rare earth compounds, such as Nd or SmCo alloys or ferrites or even Alnicos (which are still used in specific cases). Magnet material is the most important deciding factor in the fixture design. It not only decides the energy requirement for magnetization, but also greatly impacts thermal and stress consideration in the design of magnetizing fixtures. For two identical rotors with different magnet material, a particular magnetizer may not be capable of magnetizing both the rotors as the applied saturation field required for each material vary greatly and fixture thermal and safety limits can be constraining factors. In the table 1, the typical values of the saturation field for the most widely used materials are presented.

3D FE thermal simulation on a magnetizing fixture

Positioning of rotors in a magnetizing fixture

Depending upon space requirements and rotor shapes, either an internal or an external magnetizing fixture can be chosen. In an external magnetizing fixture, a rotor has to be inserted and properly oriented, if indexed. In many cases, the fixture itself orients the rotor according to its material anisotropy. Automation may be provided for rapid positioning of rotors in magnetizing fixtures.

Improved winding technology

Winding arrangement can be a key decision during fixture design. Based on each specific requirement, LE may adopt a standard round wire conductor which is an all-purpose solution, or the windings may have skewed slots that follow rotor skewing, to better saturate magnets in each stack. Recently, thanks to the latest 3D printers, LE has started adopting winding guides, which has enabled us to wind the rectangular wires easily in complex designs this greatly improves thermal dissipation and is critical especially when the goal is to reduce the cycle time.

Magnetizing fixture tolerances

One of the most frequently asked questions from LE customers is how strict the positioning tolerances need to be during magnetization. For answering the question and for giving reliable results, LE runs tolerance DOE, whereby small deviations are given to the nominal values and the effect of these deviations on the magnetization are evaluated. In this way, it is easier to decide where to put strict tolerances constraints, and where the constraints need not be strict. This helps automation design team to focus on what really matters for positioning the rotor in the magnetizing fixture.

Measurement

For a reliable system, measurement is indispensable. Some routine measurements include incoming parts mechanical inspection, characterization of the materials and the validation of the results. A typical magnetizing fixture will have measurement systems embedded to check the magnetization process. An embedded flux sense coil detects the flux exerted by the rotor, post magnetization. LE offers diverse measurement solutions to customers for quick and reliable measurement checks such as magnetic imaging systems for post magnetization validation.

Rendering of an all-in-one complete magnetization, testing and handling station for PM rotors by LE

Automation

The magnetizing system is often incorporated with automation system, for rapid rotor positioning, magnetization, measurement and extraction.
An automated process is a good option for fast and repeatable magnetization. Handling big rotors can be troublesome. This required us the design and manufacture of automatic magnetization benches for rapid magnetization and measurement of rotors, integrated seamlessly into a production line. Semi-automatic benches are also offered, where a few operations are manual. For quick inspection, identification cameras, QR readers and reject shooting procedures are implemented.
Only poka-yoke devices with safety as the highest priority are considered in the manufacturing and assembly of magnetizing stations.

Accuracy in the battery monitoring

Claudia di Sante

With the possibility of scaling on supervision circuits of batteries from 6 to 90 cells in series, the new reference Texas Instruments project for BMS, battery management system, by TI presents the advanced BQ79606A-Q1 battery precision monitor with balancer.
Engineers can rapidly release their automotive designs on the market by using the reference project, which implements the monitor for the battery in a daisy-chain configuration to create a very accurate and reliable system structure for lithium ion battery packs from 3 to 378 series, 12 V- 1.5 kV.
High-integration BQ79606A-Q1 allows an accurate monitoring of temperature and voltage levels and aids to maximise the duration of the battery and the driving autonomy. Besides, the BQ79606A-Q1 battery monitor is equipped with safe-state communication to aid system engineers to comply with requisites up to ASIL D (Automotive Safety Integrity Level D), i.e. the highest functional safety target defined by ISO 26262 regulation for road vehicles.

Acquisition to expand condition-based monitoring for Industry 4.0

Editorial Staff

Kevin Carlin, Vice President Automation and Energy Group, of Analog Devices

Among the most recent news of the specific market, there is the takeover of Test Motors, specialized in the predictive maintenance of electric motors and generators, by Analog Devices, Inc. (ADI), which so widens its portfolio for the condition based monitoring, permitting to identify appliances’ failures before they occur and therefore expensive machine downtimes.
Headquartered in Barcelona, Test Motors offers in fact products and services that detect anomalies and problems on electric motors before they cause damages to manifacturing cycles, providing indications about how and when to carry out repairs. This takeover follows the one occurred in 2018 of OtoSense, a start-up that has developed a “sensorial interpretation” software able to detect and to recognize sounds or vibrations, as well as to identify potential problems on industrial machinery or in the motor of a car before they can cause damages.
Analog Devices provides for combining the software by OtoSense with the monitoring skills by Test Motors to create solutions that offer an advanced complete snapshot of the health state of the machine, favouring the prevention of a broader range of potential failures.
«The machine maintenance largely depends on expert technicians and engineers able to detect and to diagnose problems that can lead to unplanned machine downtimes – stated Kevin Carlin, Vice President Automation and Energy Group, of Analog Devices. – There are not sufficient skilled professionals to keep pace with the demand because the number of machines to be monitored is steeply rising. Condition based monitoring applications by ADI, implemented by the takeovers of Test Motors and OtoSense, will face the problem by supplying customers with a system able to execute the complete timely detection of anomalies, to avoid unexpected expensive machine downtimes».

Sick Digital motor feedback systems for smart servo drive systems

Luca Melideo

As a result of increasing digitalization in mechanical and plant engineering, electric drive systems are increasingly faced by the challenge of having to be integrated as smart components in future-oriented overall mechatronic concepts.
The SICK range of motor feedback systems with digital HIPERFACE DSL® interface offers the required remote intelligence and communication capability for motors and servo drive systems.
The rotative sensors also meet all requirements for application-based functionality, maximum precision and dynamics as well as certified safety.
The new product families EDS35 and EDM35 are the technological highlight in this range.
With its EDS/EDM35 product family, SICK presents technologically leading singleturn and multiturn motor feedback systems with highest performance density.
The optical system achieves a singleturn resolution of 24 bits – the maximum that high-performance servo controllers can sensibly process without losses due to electric noise. Like all other digital motor feedback systems from SICK, this product family also implements the multiturn functionality of 4,096 revolutions mechanically – without buffer battery and thus wear- and maintenance-free.

Ultra-efficient electric propulsion systems for aircraft

Claudia di Sante

WEG, a global manufacturer of motors and drive technology, is teaming up with aircraft OEM Embraer to advance the aerospace industry toward the next generation of propulsion systems.
The new technology cooperation agreement seeks to accelerate knowledge in the use and integration of electric motors in aircraft propulsion, which in turn will lead to deliverable benefits such as greater energy efficiency and better environmental sustainability.
An electric-powered demonstrator already has its first flight scheduled for 2020.
The electrification process forms part of extensive efforts which aim to ensure the environmental commitments of the aerospace sector.
Cooperation between the two research teams will support the creation of innovative technologies that generate opportunities for future aerospace platforms, and potentially develop new market segments.
After testing the newly developed technologies in the laboratory, an aerospace platform will be used for the integration and testing of complex systems under real operating conditions. A small, single-engine aircraft, based on the EMB-203 Ipanema, will be used as the test bed for primary evaluation, before the first demonstrator flight next year.

HBM digital torque transducer

Corrado Luca Franchini

With electric motors and drives now operating at significantly higher speeds, electromobility testing poses a greater challenge for engineers working on R&D or production lines. To overcome this challenge, measurement specialist, HBM has launched the T40B torque sensor which delivers greatly increased revolutions per minute for a selection of measuring ranges of 1, 2, and 3 kNm – up to 23.000 rpm – making it ideal for many types of applications including test benches, end-of-line tests (EoL) and process monitoring.
The T40B torque provides users with precise, reliable measurements first time, eliminating the risk of errors and the need for repeat tests, which can be costly and time consuming.
The sensor has an integrated, magnetic rotational speed measuring system, enabling automotive engineers to test the efficiency of the drive train with a range of motor vehicles. It also operates with analog or digital interfaces making it compatible with different types of test bench systems.