Efficiency trends in electric machines and drives

doi:10.1016/j.enpol.2008.09.042

Energy Policy

Volume 36, Issue 12, December 2008, Pages 4336-4341

https://doi.org/10.1016/j.enpol.2008.09.042 Get rights and content

Abstract

Almost all electricity in the UK is generated by rotating electrical generators, and approximately half of it is used to drive electrical motors. This means that efficiency improvements to electrical machines can have a very large impact on energy consumption. The key challenges to increased efficiency in systems driven by electrical machines lie in three areas: to extend the application of variable-speed electric drives into new areas through reduction of power electronic and control costs; to integrate the drive and the driven load to maximise system efficiency; and to increase the efficiency of the electrical drive itself. In the short to medium term, efficiency gains within electrical machines will result from the development of new materials and construction techniques. Approximately a quarter of new electrical machines are driven by variable-speed drives. These are a less mature product than electrical machines and should see larger efficiency gains over the next 50 years. Advances will occur, with new types of power electronic devices that reduce switching and conduction loss. With variable-speed drives, there is complete freedom to vary the speed of the driven load. Replacing fixed-speed machines with variable-speed drives for a high proportion of industrial loads could mean a 15–30% energy saving. This could save the UK 15 billion kWh of electricity per year which, when combined with motor and drive efficiency gains, would amount to a total annual saving of 24 billion kWh.

Introduction

Electrical machines have advanced significantly in recent years due to the introduction of new materials. New electrical steels have reduced losses and rare earth permanent magnet materials have provided a ‘lossless’ source of magnetic flux. Recent advances in construction methods have reduced winding losses, so there is a continued trend to increase efficiency. For large electrical machines efficiency is already high and so, although significant, the potential gains are limited. Greater gains are possible in smaller machines, which may be only 50% efficient.

Variable-speed drives are created when a motor is combined with a power electronic converter. By introducing variable speed to the driven load, it is possible to optimise the efficiency of the entire system, and it is in this area that the greatest efficiency gains are possible.

This paper has three major sections: Section 2 covers statistics of energy consumption and current predictions of possible savings using existing technology; Section 3 describes the current state of the art: and Section 4 covers future, longer-sighted possibilities.

Section snippets

Energy consumption

UK Energy Consumption Statistics published by the Department of Trade and Industry (2000) give a breakdown of energy consumption by fuel, by sector and by final end use, but do not explicitly reveal the energy consumed by electrical motor-driven systems. Studies promoted by the European Commission (De Keulenaer et al., 2004; European Commission Joint Research Centre on Electric Motor Efficiency, 2004; EU SAVE II Project, 2001; Haataja and Pyrhonen, 1998) state that motor-driven systems use

Current state of the art

Industrial motor systems are dominated by induction motors running at effectively constant speed. Variable-speed drives, in which the speed of the machine is controlled by a power electronic converter, are taking an increasing size of the market and in 2004 accounted for 25% of new systems (De Almeida et al., 2005). The efficiency of the electrical system in isolation will first be considered, before progressing to the entire system where, with the addition of variable-speed drives, much larger

Future advances to 2050 and beyond

The function of an electrical drive is to transfer electrical energy to mechanical energy and vice versa. This is currently achieved almost exclusively via a magnetic field. The first question to ask is: ‘Are there any new processes of energy conversion that may replace this method in the next one hundred years?’ The answer is simple: none are known of at the time of writing. Competing systems, such as electric fields are several orders of magnitude less power-dense or, in the case of

Conclusions

By adopting known, proven concepts, it is possible to dramatically increase the efficiency of systems driven by electrical machines and reduce total electricity consumption by over 7%. There is a trend for increasing efficiency within the electrical machine itself, but the greatest gains are at system level when the machine is combined with a power electronic converter to create a variable-speed drive. The main barriers to this lie in the initial cost of a variable-speed drive, even though in

References (37)

H. Auinger
Determination and designation of the efficiency of electrical machines
IEE Power Engineering Journal
(1999)
H. Auinger
Efficiency of electric motors under practical conditions
IEE Power Engineering Journal
(2001)
F. Blaabjerg et al.
The future of power electronic processing and conversion
IEEE Transactions on Industry Application
(2005)
A. Boglietti et al.
International standards for the induction motor efficiency evaluation: a critical analysis of the stray loss determination
IEEE Transactions on Industry Application
(2004)
D.A. Casada et al.
Efficiency testing of motors powered from pulse width modulated adjustable speed drives
IEEE Transactions on Energy Conversion
(2000)
K.Y. Cho et al.
Sensorless control of a PM synchronous motor for direct drive washer without rotor position sensors
Electric Power Applications, IEE Proceedings
(2004)
S.R. Das
The sensible superconductor
IEEE Spectrum
(2002)
A.T. De Almeida et al.
Technical and economical considerations in the application of variable-speed drives with electric motor systems
IEEE Transactions on Industry Applications
(2005)
H. De Keulenaer et al.
Energy-efficient motor-driven systems. EU-sponsored programme
(2004)
Department for Environment, Food and Rural Affairs, 2006. Briefing note: BNM02: minimum efficiency performance...

Department of Trade and Industry

National statistics on energy consumption in the United Kingdom

(2002)

Drives and Controls, 2004. Dyson's turbocharged SR motor can phone home....

EU SAVE II Project, 2001. Promotion of energy efficiency in circulation pumps, especially in domestic heating systems....

European Commission Joint Research Centre on Electric Motor Efficiency, 2004:...

H. Fang et al.

Development of Fe-sheathed MgB₂ wires and tapes for electric power applications

IEEE Transactions on Applied Superconductivity

(2005)

J. Haataja et al.

Improving three-phase induction motor efficiency in Europe

IEE Power Engineering Journal

(1998)

Hultman, L.O., Jack, A.G., 2003. Soft magnetic composites—materials and applications. In: IEEE Conference, IEMDC03, 1...

International Standard CEI IEC 34-2

Rotating Electrical Machines, Part 2. Methods of Determining Losses and Efficiency of Rotating Machinery from Tests

(1996)

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^☆: While the Government Office for Science commissioned this review, the views are those of the author(s), are independent of Government, and do not constitute Government policy.

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Efficiency trends in electric machines and drives☆

Abstract

Introduction

Section snippets

Energy consumption

Current state of the art

Future advances to 2050 and beyond

Conclusions

Determination and designation of the efficiency of electrical machines

IEE Power Engineering Journal

Efficiency of electric motors under practical conditions

IEE Power Engineering Journal

The future of power electronic processing and conversion

IEEE Transactions on Industry Application

International standards for the induction motor efficiency evaluation: a critical analysis of the stray loss determination

IEEE Transactions on Industry Application

Efficiency testing of motors powered from pulse width modulated adjustable speed drives

IEEE Transactions on Energy Conversion

Sensorless control of a PM synchronous motor for direct drive washer without rotor position sensors

Electric Power Applications, IEE Proceedings

The sensible superconductor

IEEE Spectrum

Technical and economical considerations in the application of variable-speed drives with electric motor systems

IEEE Transactions on Industry Applications

Energy-efficient motor-driven systems. EU-sponsored programme

National statistics on energy consumption in the United Kingdom

Development of Fe-sheathed MgB2 wires and tapes for electric power applications

IEEE Transactions on Applied Superconductivity

Improving three-phase induction motor efficiency in Europe

IEE Power Engineering Journal

Rotating Electrical Machines, Part 2. Methods of Determining Losses and Efficiency of Rotating Machinery from Tests

Development of Fe-sheathed MgB₂ wires and tapes for electric power applications