Environmental and Life Cycle Cost Analysis of a Switched Reluctance Motor

8/4/2019 Environmental and Life Cycle Cost Analysis of a Switched Reluctance Motor

1/4

Proceedings of the 2008 International Conference on Electrical Machines Paper ID 1221

978-1-4244-1736-0/08/$25.00 2008 IEEE 1

Environmental and Life Cycle Cost Analysis of aSwitched Reluctance Motor

E. Martnez, P. Andrada, B. Blanqu, M. Torrent, J.I. Perat, J.A. SnchezGrup dAccionaments Elctrics amb Commutaci Electrnica (GAECE)

EPS dEnginyeria de Vilanova i la Geltr, Departament dEnginyeria ElctricaTechnical University of Catalonia (UPC)

Avinguda Victor Balaguer s/n, 08800 Vilanova i la Geltr

Barcelona, SpainE-mail: [email protected]

Abstract-This paper presents an analysis of the environmentaland life cycle costs of a switched reluctance motor (SRM) drive.The analysis was carried out according to the Energy-UsingProduct Directive (EuP 2005/32/EC) and following theMethodology for the Eco-Design of Energy-Using Products(MEEUP methodology). The base case model adopted is an 8/6SRM with 1.5 kW of output power that can be considered

representative of the small power range. The analysis shows thatSRMs could generate large savings comparable to or even betterthan those of Eff1 three-phase induction motors in the use phase.

I. INTRODUCTIONThe use of energy-efficient motors can save enormous

quantities of energy and reduce the emission of greenhousegases [1]. Today, it is not enough to take into account theefficiency of an electric motor: all life cycle costs (production,use and disposal) must be considered. The Energy-UsingProducts Directive (EuP 2005/32/EC) sets the requirementsthat energy-using products must fulfill for them to be put on

the market and/or into service. To evaluate whether and towhat extent a product fulfills the Directives criteria, theMEEUP methodology (Methodology for the Eco-Design ofEnergy-Using Products) was developed [2] [3]. Althoughenergy-efficient motors have generally been associated withthree-phase induction motors [4] [5], switched reluctancemotors (SRMs) are claiming their place in the electric motormarket because of their simple, robust construction, faulttolerance capability and high efficiency. In this paper, theenvironmental and life cycle costs of an SRM are analyzedaccording to EuP 2005/32/EC and following the MEEUPmethodology, for a sample base case model that isrepresentative of the small power range.

II. SRMDRIVE DESCRIPTIONSRM drives have some drawbacks: they require an

electronic control and shaft position sensor, a huge capacitor isneeded in the DC link and the double salient structure causesnoise and torque ripple. They are, however, gainingrecognition in the electric drive market because of their simple,robust construction, low expected manufacturing cost, faulttolerance capability, high efficiency and high torque-to-inertiaratio.

The base case model adopted is an 8/6 SRM (300 V, 1.5 kWof output power and IEC-90 frame) that can be said to berepresentative of the small power range (Fig. 1). The SRM,whose specifications are given in Appendices A and B, wasdesigned and built for the authors but has not beencommercialized yet.

Several eco-design considerations were taken into account inthe design, namely:

The number of materials should be reduced. The number of non-recyclable parts (i.e. plastics)

should be minimized.

The motor should be easily assembled anddisassembled.

The windings should be easy to remove.The SRM is controlled using the drive depicted in Fig. 2. The

power converter is a four-phase, asymmetric half-bridge,classic converter, with two IGBTs and two fast diodes perphase. The rotor position is determined by means of an encoder

or an ensemble formed by a slotted disk and three opto-interrupters placed inside the SRM.

Fig. 1. Cutaway view of the 8/6 SRM


2/4

Proceedings of the 2008 International Conference on Electrical Machines

2

Fig. 2. A schematic block diagram of the SRMdrive

The speed controller, a proportional integral (PI) controller,generates a current command based on the error between thereference speed and the motor speed. The current in theappropriate phase is regulated at the reference current byhysteresis control. The firing angle calculator computes theturn-on and turn-off angles at every instant, taking into accountthe actual speed and reference current.

III. ENVIRONMENTAL IMPACT AND LIFE CYCLE COSTSThe MEEUP methodology provides an Excel spreadsheet for

estimating the environmental impact. First of all, study data iscollected, including materials, energy use and economic datafor the various life stages of the products. The model thentranslates these inputs into quantifiable environmental impacts.

The description of the base case is the result that concernsthe products (Bill of Materials), including packaging, theestimated volume of the packaged product, the consumption ofenergy and other resources during the production phase, theuse phase and finally a scenario for recycling, re-use anddisposal (Tables I and II and Appendix C).

Table III shows the life cycle impact of an 8/6 SRM, forwhich a lifetime of 12 years, 4000 hours per year of operation

and an average load factor of 60 % are considered. The lifecycle indicators are divided into three blocks: main indicators,emissions to air and emissions to water. It is important to pointout that the Table presents a loss-based impact analysisbecause an SRM is considered to be an energy converterandnot an end use device. Therefore, only losses are consumedinside the SRM, with the remaining energy being transmittedas mechanical power.

The life cycle costs are summarized in Table IV. In thistable the product list price is just an estimate. The electrical

energy costs are computed considering 4000 hours of operationper year and the price of electricity in Spain. The repair andmaintenance costs are negligible because motors of less than 5kW are not generally repaired upon failure.

TABLE IBILL OF MATERIALS

MATERIALS kg

Electrical steel 7.46

Other steel 1.50

Aluminium 4.48

Copper 2.50

Insulation material 0.01

Impregnation resin 0.20

Paint 0.06

Plastics 0.53

Electronics 0.36

Packing material 1.50

TABLE IIUSE PHASE

VARIABLES

Lifetime (years) 12

Global efficiency (%) 82.6

Operating hours 4000


3/4


3

TABLE III

ENVIRONMENTAL IMPACTS (PER PRODUCT)

MAIN INDICATORS

Total energy GER(1) (MJ) 162071

Of which, electricity (in primary MJ) 160066

Water process (l) 10804

Waste, non-hazardous landfill (g) 256458

Waste, hazardous incinerated (g) 4889

(1) Gross energy requirements

EMISSIONS TO AIR

Greenhouse gases in GWP100 (kg Co2 eq) 7128

Ozone depletion emissions (mg R-11 eq) negligible

Acidification potential (g SO2 eq) 42395

VOCs (g) 75

Heavy metals (mg Ni eq) 3197

Particulate matter (g) 3832

EMISSIONS TO WATER

Heavy metals (mg Hg/20) 1116

Eutrophication (g PO4) 11

TABLE IV

LCC FOR SRM

MAIN INDICATORS

Product list price 384

Electrical energy 5795

Repair and maintenance costs ---

IV. CONCLUSIONSAn environmental and life cycle cost analysis of an 8/6 SRM

drive that can be considered to be representative of the small power range is described in this paper. The analysis wascarried out according to EuP 2005/32/EC and following theMEEUP methodology. From the analysis it can be concludedthat SRMs could generate large savings, mainly due to theirhigh efficiency. In the use phase, the savings generated bySRMs are comparable to or even better than those ofEff1three-phase induction motors. Unfortunately, a drawback of the

MEEUP methodology is that it does not reflect one of the mainadvantages of SRMs, which is the ease with which its variousparts and materials can be separated in the disposal phase.

SRMs have not yet reached the status of standardcommodity products; as a result, OEMs, who are mainlyinterested in motor prices as they do not pay operating costs,do not consider them to be a good choice [5]. The production phase of SRMs must improve so that initial costs can bereduceda clear disadvantage is the high waste of magneticsteel in punchingbut this is difficult to achieve if there arefew potential purchasers. Regulatory measures focusing onminimum efficiency standards for motors would be a first stepto removing inefficient motors from the market and pushingSRMs to the forefront.

ACKNOWLEDGMENTS

This research was supported by the Spanish Ministry ofEducation andScience and the ERDF (DPI2006-09880).

REFERENCES[1] A.T. de Almeida, F.J.T.E. Ferreira, D. Both. Technical and Economical

Considerations in the Application of Variable-Speed Drives withElectric Motor Systems IEEE Transactions on Industry Applications,Vol. 41, No.1, January/February 2005, pp 188-198.

[2] http://ec.europa.eu/energy/demand/legislation/eco_design_en.htm[3] VHK, DG ENTR (European Commission) Methodology Study Eco-

design for Energy using Products. November 2005.[4] A.T. de Almeida, F.J.T.E. Ferreira, J. Fong, P. Fonseca. EUP Lot 11

Motors FINAL, February 2008.[5] A.T. de Almeida, P. Fonseca, H. Falkner, P. Bertoldi. Market

Transformation of Energy-Efficient Motor Technologies in the EU.Energy Policy 31 (2003), pp. 563-576.

APPENDIX A

LAMINATIONS OF THE FOUR-PHASE 8/6SRM


4/4


4

APPENDIX B

SRM DATA

PARAMETER SYMBOL VALUE

Stator outer diameter D0 150 1 mm

Stack length L 95 mm

Stator inner diameter Di 132 mm

Stator airgap diameter Ds 80.8 mm

Rotor airgap diameter D 80 mm

Airgap g 0.4 mm

Stator pole arc s 20.68

Rotor pole arc r 23.07

Stator pole width bs 14.5 mm

Rotor pole width br 16 mm

Stator yoke thickness hy 9 mm

Rotor yoke thickness hn 9 mm

Stator slot depth hs 25.6 mm

Rotor slot depth hr 16 mm

Shaft diameter De 30 mm

Shaft diameter (drives end) Dout 24 mm

Lamination steel FeV 270-50 HA

Number of coils per pole Np 97

Wire diameter dc 1.18 mm

Insulation class H

APPENDIX C

GLOBAL EFFICIENCY OF THE FOUR-PHASE 8/6SRMDRIVE

Documents

Environmental and Life Cycle Cost Analysis of a Switched Reluctance Motor