Application Trends of Sensorless AC Motor Drives in Europe

IEEJ Journal of Industry ApplicationsVol.3 No.2 pp.97–103 DOI: 10.1541/ieejjia.3.97

Review Paper

Application Trends of Sensorless AC Motor Drives in Europe

Sadayuki Sato∗a)Member, Kozo Ide∗∗ Senior Member

(Manuscript received April 15, 2013, revised Sep. 27, 2013)

This paper describes application trends of sensorless AC motor drives in Europe, where strict standards on energysaving are in effect. To meet their standards, each producer of AC motor drives in Europe has own strategy with specificmachine design and control techniques. Generally, variable torque applications such as fans, pumps and compressorsaccount for approximately 70% of the European market. These applications employ position and speed sensorlessdrives because of the advantages of reduced cost and volume, and increased reliability due to the elimination of theposition sensor and related cabling connections. In this paper, first the market trends of AC motor drives in Europe aredescribed. Second, the market penetration of sensorless AC motor drives is briefly discussed. Finally, some real-lifeapplications are introduced.

Keywords: Sensorless, AC motor, Application, Europe

1. Market Trends of AC Motor Drives in Europe

Due to issues like oil depletion and global warming, theEuropean market has been moving forward quickly with sev-eral energy saving and efficiency measures compared to otherworld regions. The measures will be required not only for in-dividual components of a system like electrical motors, butalso for complete applications. These measures will be dif-fused throughout the European region by means of the ErP(formerly EuP) directive and IEC standards. One of the mostnotable IEC standards defines the efficiency level required ofinduction motors classified by their power range, number ofpoles and input frequency. The efficiency levels were definedas three categories named IE1, IE2, and IE3. Recently, afourth category was added (IE4) that applies not only to in-duction motors but also all other types of electric motors. InFig. 1 each efficiency level is shown for reference.

According to these standards (1)–(3), all induction motors soldin the European market from the beginning of 2011 mustcomply with IE2 requirements in the entire power range.From 2015, all induction motors sold in the power range be-tween 7.5 kW and 375 kW must comply with IE3, and from2017 induction motors from 0.75 kW must comply with IE3as well. Other types like permanent magnet or synchronousreluctance motors must comply with IE4. Furthermore, theErP directive mandates that energy saving shall also be regu-lated for each application, meaning that efficiency labels (SeeFig. 2) will need to be affixed to the products. For appli-cations like circulators, water pumps, and fans this will bemandatory from 2013 (4)–(6), and other applications will follow.This way, energy saving regulations in Europe are not limitedto the electric motor, but also to the application itself.

a) Correspondence to: Sadayuki Sato. E-mail: [email protected]∗ YASKAWA EUROPE GmbH

Hauptstrasse 185, Eschborn 65760, Germany∗∗ YASKAWA ELECTRIC CORPORATION

2-13-1, Nishimiyaichi, Yukuhashi, Fukuoka 824-8511, Japan

Due to these energy saving regulations and magnet priceissues, the market for European motor drive companies is ex-tremely difficult. The price increase of neodymium rare earthmagnets was especially serious, considering that it jumpedtwelve fold in the period between 2009 and 2011, as shownin Fig. 3. Due to this fact, many large drive companies startedrecommending magnet-less technologies like synchronousreluctance or IE4 induction motors. Some examples can beseen below:•ABB, Europe’s largest drive company, launched a com-

plete package consisting of Synchronous reluctancemotor with their dedicated drive in the entire powerrange (7)–(10). The drive employs the sensorless directtorque control (DTC) method (10).•KSB, Europe’s largest pump company, acquired Italian

motor company REEL, and has since been mountingsynchronous reluctance motors on their pumps (11) (12), andhas developed a special drive for this purpose. The driveuses a hybrid sensorless control method (13), combininghigh frequency injection and flux observer.•VEM and WEG (Brazilian company), two large motor

companies in Europe, have launched IE3 (14) and IE4 in-duction motors (15).• Control Techniques (LeroySomer) has only launched

original interior permanent magnet synchronous motor(IPMSM) and their drive with sensorless control on alarge scale (16) (17).• Ziehl Abegg and ebm papst, both large European fan

manufacturers, have adopted Brush-less DC motors withFerrite magnets into their original fan (18) (19) in order toachieve a low-cost solution.

As seen above, there is a wide variety of technologies,ranging from synchronous reluctance, IE3/IE4 induction,IPMSM, and brushless DC motors. All of these motors re-quire a special drive for optimal performance in the entirespeed range. As a result of these measures and other factors,the drive market in Europe has grown from 0.1% of the to-tal motor market in 1998 (20), to about 60% of the total motor

c© 2014 The Institute of Electrical Engineers of Japan. 97

Application Trends of Sensorless Drives in Europe（Sadayuki Sato et al.）

market in 2012.Variable torque applications such as fan, pump and com-

pressor account for about 70% of the motor applications inEurope (20). In this application, a small footprint is preferred,requiring a compact motor and drive. This also has disad-vantages, such as heat and high frequency drive issues. Un-der these conditions it is difficult to use sensors such as en-coders, which are susceptible to high heat and require addi-tional hardware on the drive side. To overcome these issues,the market has gradually gravitated towards sensorless motorcontrol. Yaskawa has been at the one of the global forefrontin the research and development of sensorless motor controlmethods for PM motor, and there are a number of success-

Fig. 1. Efficiency levels (IE1, IE2, IE3 and IE4) for50 Hz (1) (2)

Fig. 2. Example of label for the Europump voluntary la-beling scheme (4)

Fig. 3. Magnet Price Tendency from 2009 to 2013. Thisis given by ZVEI Die Electroindustrie

ful applications that use these innovations in Europe. In thispaper, Yaskawa’s sensorless motor control techniques are de-scribed and several application examples for PM motor drivesare introduced later chapter.

2. Market Penetration of Sensorless AC MotorDrives in Europe

As introduced in the previous chapter variable torque appli-cations such as fan, pump and compressor account for around70% of the European market. Such applications require com-pactness and robust features, such as high resistance againsttemperature and mechanical vibration on motor and drive forsystem configuration. This means that it is difficult to use anysensors under these conditions. Speed sensors are especiallysensitive because they are really weak against disturbances.To solve these technical problems, the needs of sensorlessAC motor drive have expanded. On the other hand, to pur-sue more compactness on real application in Europe, motorsize has been gradually reduced, so in order to get same out-put power higher speeds are required. In case of an inductionmotor, a shaft might be broken with high speed drive by hightemperature due to high loss on the rotor. Consequently, theseapplications prefer to use an IPMSM, which has no electricallosses on their rotor, rather an induction motor, recently.

The high efficiency IPMSM drive employing general-purpose inverters was first commercialized in 1995. Sincethen, the IPMSM drive has been popular due to energy sav-ing and down-sizing advantages, and the application rangehas expanded to fans, pumps to lifts. Especially, in the caseof the drive for lift traction motors IPMSM is becoming theworldwide industry standard. The performance of perma-nent magnets has progressed considerably, and the IPMSMhas been expanded to 0.4 kW–300 kW power range. Sincethe IPMSM shows the prominent characteristic on magnetic

Fig. 4. Position and speed estimation with a hybridmethod, where uin j is the test: test signal of high-frequency voltage, us is the stator voltage, is is the sta-tor current, ˆ means estimated value, ω expresses angularspeed, θ expresses rotor phase angle, G1 and G2 are theweighting factor

98 IEEJ Journal IA, Vol.3, No.2, 2014


Fig. 5. Position and speed estimator with HFIM

Fig. 6. Position and speed estimator with back EMFbased method

saliency due to the interior magnet, it is compatible to thehigh frequency injection method (HFIM). To operate in theentire speed range, the hybrid sensorless control as shown inFig. 4 is employed (21)–(23). The hybrid sensorelss control con-sists of the HFIM as shown in Fig. 5 and the back EMF basedmethod as shown in Fig. 6. In 2008 the first commercial gen-eral purpose inverter with sensorless control based on HFIMwas launched. Now, four years have passed, and the appli-cation field has been expanded. Next chapter introduces fouryears of industrial experience with sensorless IPMSM drivebased on HFIM. As successful special applications, a bear-ing cover inserter machine, a cutting concrete machine, andothers are introduced there.

3. Application Example

3.1 Bearing Cover Inserter Machine Figure 7shows a configuration of a machine that inserts bearing cov-ers. The piston that drives the bearing into position is pow-ered by hydraulics, and the hydraulic pressure is created bya hydraulic pump driven by a IPMSM. The operation of thishydraulic piston is highly dynamic; during insertion of thebearing cover very high torque is needed very quickly, andthe PM motor needs to be able to keep this high torque at lowspeeds for a few seconds while the cover is being affixed tothe bearing. Also, in order to ensure short tact times for theproduct line, the piston must also retract to the default posi-tion very quickly once the bearing cover is affixed. Thereforethe motor drive must satisfy the following specifications:•Acceleration up to nominal speed within 100 ms (Piston

starts to move)•High impact torque such as 200% to 300% of nominal

torque during constant speed (Bearing cover insertion isstarted)

Fig. 7. Bearing cover inserter machine configuration

Table 1. Specification of the IPMSM for applied theBearing cover Machine

Fig. 8. Operation test results

•Keep around 100% of nominal torque with low speed as200 min−1 (During cover insertion)•Acceleration to opposite nominal speed within 100 ms

(Piston is moved back to default position)Previously a servo motor was used to achieve these strict

specifications, which provided a resolver for motor speed.Now the system has been changed to use oil for cooling, andthe addition of an oil tank means there is no room for theresolver. Therefore sensorless control is needed. The motorparameters are given in Table 1; the motor specifications statethat the stator is to have concentrated windings and the rotoris to be of the IPM type.

The results of experiments with an IPMSM driving the ac-tual machine are shown in Fig. 8. In this experiment all re-



Fig. 9. Concrete Cutting Machine Configuration

Table 2. Specification of the IPMSM for applied theConcrete cutting machine

quired operations were reproduced; all of the conditions weresatisfied without any problems.

3.2 Concrete Cutting Machine Figure 9 shows theoutline of the concrete cutting machine. This system has sev-eral advantages: it is easy to transport and assemble by any-one, anywhere, because it is compact and lightweight. Pre-viously this system had used a high-speed induction motorwith a gear box, but this configuration created extremely hightemperatures on the rotor, which led to the drive shaft break-ing. Furthermore the machine was heavy, which requiredlarge amounts of time and labor for maintenance. To solvethese problems a motor with high energy efficiency and lowweight is needed, so it has been decided to use a PM motor.The lower power range and removal of the gear box furtherreduce costs and machine weight. Finally, the introductionof a PM motor to this system is a huge success because oflonger life-time, high reliability, space saving, lower weight,and lowered costs. The detailed PM motor parameters areshown in Table 2. The rotor of this motor is of the IPM type,with a saliency ratio Lq/Ld that seems to be higher than nor-mal IPMSMs.

This system is frequently used outdoors in both northernEurope and North America. These regions can get quite cold(−20◦C to −30◦C) in winter and quite hot (over 40◦C) insummer, so the system needs to be able to survive in theseenvironments. On the other hand, reliability for a drive sys-tem must make more progress. For these reasons, sensorlessspeed control is needed to assure reliable performance in se-vere environmental conditions.

Fig. 10. In case of cutting concrete

Fig. 11. Wave-forms during cutting concrete. Blue:Feed motor voltage (10 [V/div]), Red: Feed motor current(1.55 [A/div]), Purple: Feed motor power (38.4 [W/div]),Green: heatsink temperature (19.4 [◦/div]), Light blue:Feed motor status

Most concrete contains rebar (metal bars) for reinforce-ment (See Fig. 10), so over 150% of nominal torque is neededmany times suddenly during cutting when the saw blade cutsthese metal bars. If the blade’s rotational speed fluctuates toomuch, the cut surface can be rendered unacceptable. There-fore the motor drive has to handle large impact loads withoutlarge speed fluctuations. Normally a speed fluctuation of over5% is unacceptable.

The results of testing with the actual machine are givenin Fig. 11. This test was performed by cutting real concretewith rebar included using the smallest blade. The PM mo-tor drive rotation was 3440 min−1. Motor current and motorspeed were both very stable, therefore the maximum speedfluctuation of 5% was achieved without problems.

3.3 Compressor Figure 12 shows an air compressorsystem. The conventional system employed an induction ma-chine driven with commercial power supply. Getting the im-portance to save energy, the PM machine driven by invertersystem is replaced with the conventional one. The feature ofsaving-space is one of the attractive features to employ PMmachine. The sensorless drive is required in case of directdrive with the reason that the position sensor may fail in the



Fig. 12. Air compressor configuration

Table 3. Specification of the IPMSM for applied thecompressor

environment of high temperature, humidity, and mechanicalvibration.

The air pressure of the compressor is controlled by un-loader and check valves. In such case, the machine is re-quired to start under heavy load condition. Opening un-loader valve, the machine connected to the compressor actsat 3% of the rated speed sustaining load about 200 to 300%of the rated torque.

The specification of 0.4 kW IPMSM is shown in Table 3.Figure 13 shows the waveform of the speed and torque.

Before starting the machine, the load torque was applied tothe rating. In this condition, the machine was controlled tozero speed, and the torque needed 200% of the rated valuein the acceleration of the speed. Then, the speed reached tothe rated speed within 0.5 sec. The hybrid sensorless controlperformed well under tested severe load conditions.

3.4 Injection Molding Machine Figure 14 shows thestandard structure of the injection molding machine. In thisapplication, there are controlled processes such as molding,plasticization, injection, and extrusion, where servo drives

Fig. 13. Acceleration test results with 100% of ratedtorque on the compressor: top: Real speed wave-form,middle: Reference torque current wave-form, bottom:Estimated speed wave-form

through timing belts and gears is usually employed shownin Fig. 14(a). As the sensorless-drive, the plasticization is fo-cused attention on. In the process, the reciprocating screwkneads melted plastic uniformly, and the back-pressure iscontrolled to make value of plastic and the pressure in theheat cylinder constant. The drive through belts and gearscauses the following problem:• Torque ripple causes due to mechanical factor• Precise back-pressure control is difficult because of the

indirect connection between the machine and the loadcell• Centering of the screw is difficult due to radial force in

case of timing belts connectedIn order to solve the solution, direct drive without belts

and gears are required. The hybrid sensorless control systemis employed to realize the direct drive. Figure 14(b) showsthe system configuration. Figure 15 shows the IPMM de-signed for an injection molding machine. The machine hasthe hollowed rotor connected to the screw driving shaft in theplasticizing unit.

For the sensorless control, the following conditions are re-quired in this application:• Initial pole position is detected at stand-still• Starting under heavy load condition and the response to

reach the rated speed in 0.1 to 0.2 s• Servo-locked position control keeping zero speed under

rebound torque caused in injection modeThe sensorless control system met all conditions. The

initial pole position was detected within the error angle of±10 deg (elec.) and/or ±1 deg (mech.). Detailed explana-tion is in Ref. (24). Figure 16 shows the waveform in speedcontrol mode, where the constant heavy load about 100% ofthe rated torque is kept in constant. The speed control modeneeds the controllable speed range from zero to the ratedspeed. Starting of the machine under heavy load was possi-ble. The response of the speed acceleration and deceleration



(a) In-direct drive configuration (b) Direct drive configuration

Fig. 14. Injection molding machine

Fig. 15. IPMSM for the injection molding machine

Table 4. Specification of the IPMSM for the injectionmolding machine

Fig. 16. Waveform in speed control mode

were achieved within 0.2 s. Figure 17 shows the waveform inposition control mode, where the position varies along withthe command under the heavy load of about 80% of the ratedtorque. The performance of the servo-locked position controlwas also satisfied to suppress the movement against the re-bound torque caused in injection mode. The specification ofthe tested IPMSM is shown in Table 4.

Fig. 17. Waveform in position control mode

4. Conclusion

This paper introduced application trends of sensorless ACmotor drives in Europe, where strict standards on energy sav-ing are in effect. In order to meet these standards, each pro-ducer of AC motor drives in Europe has own strategy withspecific machine design and control techniques. Generally,variable torque applications such as fan, pump and compres-sor accounted for almost 70% of the European market. Suchapplications use drives with sensorless position and speedcontrol. Due to the price increase of rare earth magnets,many large drive companies started recommending magnet-less technologies with synchronous reluctance or IE4 induc-tion motors. Due to compactness and high speed issue, how-ever, an IPMSM has still been expanded to European marketon specific applications, some of which were introduced inthis paper. In this way, the use of sensorless AC motor driveshas been steadily increasing through the European market;spreading to other applications like concrete bearing coverinserter machine, concrete cutting machine and so on.

References

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( 2 ) The International Electrotechnical Commission (IEC): “Rotating electricalmachines-Part31: Selection of energy-efficient motors including variablespeed applications-Application guide”, IEC 60034-31, Edition 1.0, pp.5–41(2010)

( 3 ) A.T. de Almeida, F.J.T.E. Ferreira, J. Fong, and P. Fonseca: “EuP Lot 11Motors”, pp.14–137 (2008)

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Sadayuki Sato (Member) received the Ph.D. degrees in system con-trol from the graduate school of science and engineer-ing, Saga University, Japan, in 2004. From 1996 to2003, he was working at Nidec Techno Motor Cor-poration, Iizuka, Japan, where he developed mainlyan Induction synchronous motor and Brushless DCmotor. From 2004 to 2007, he was working at Sam-sung R&D Institute Japan, Osaka, Japan, where heresearched DD motor control method for Drum typewashing machine and its detection system. From

2007 to 2009, he was working at Yaskawa Electric Corporation, Yukuhashi,Japan, where he developed new motor control method for an Inverter. In2010, he moved to Yaskawa Europe GmbH, Germany, where he is currentlyan application specialist.

Kozo Ide (Senior Member) received the B.S., M.S., and Ph.D. de-grees in electrical engineering from the Kyusyu In-stitute of Technology, Kitakyushu, Japan, in 1991,1993, and 1996, respectively. From 1991 to 1992,he was a Visiting Resercher at L’Aquila University,Italy, supported by the Italian government. In 1996,he joined Yaskawa Electric Corporation, Kitakyusyu,Japan, where he is currently a Manager of Environ-ment and Energy Business Drives Division. From2002 to July 2003, he was a Visiting Resercher with

Siemens AG, Germany. His current research interests include control tech-nology for an ac machines and energy conversion systems.


Application Trends of Sensorless AC Motor Drives in Europe

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