Selection of energy-efficient motors including variable speed applications - Application guidelines
1 Scope
This document provides a guideline of technical and economical aspects for the application of energy-efficient electric AC motors. It applies to motor manufacturers, OEMs (original equipment manufacturers), end users, regulators, legislators and other interested parties.
This document is applicable to all electrical machines covered by IEC 60034-1, IEC 60034-30-1 and IEC TS 60034-30-2.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 12668.902-2021 Adjustable speed electrical power drive systems - Part 9-2: Ecodesign for power drive systems, motor starters, power electronics and their driven applications - Energy efficiency indicators for power drive systems and motor starters (IEC 61800-9-2:2017, IDT)
GB/T 32877-2022 Specific test methods for determining losses and efficiency of converter-fed AC motors (IEC 60034-2-3:2020, IDT)
IEC 60034-1 Rotating electrical machines - Part 1: Rating and performance
IEC 60034-2-1 Rotating electrical machines - Part 2-1: Standard methods for determining losses and efficiency from tests (excluding machines for traction vehicles)
IEC 60034-2-3 Rotating electrical machines - Part 2-3: Specific test methods for determining losses and efficiency of converter-fed AC motors
Note: GB/T 32877-2022, Specific test methods for determining losses and efficiency of converter-fed AC motors (IEC 60034-2-3:2020, IDT)
IEC 60034-12 Rotating electrical machines - Part 12: Starting performance of single-speed three-phase cage induction motors
IEC 60034-30-1 Rotating electrical machines - Part 30-1: Efficiency classes of line operated AC motors (IE code)
IEC TS 60034-30-2 Rotating electrical machines - Part 30-2: Efficiency classes of variable speed AC motors (IE-code)
IEC 60072 (all parts) Dimensions and output series for rotating electrical machines
IEC 61800-9-1 Adjustable speed electrical power drive systems - Part 9-1: Ecodesign for power drive systems, motor starters, power electronics and their driven applications - General requirements for setting energy efficiency standards for power driven equipment using the extended product approach (EPA) and semi analytic model (SAM)
IEC 61800-9-2 Adjustable speed electrical power drive systems - Part 9-2: Ecodesign for power drive systems, motor starters, power electronics and their driven applications - Energy efficiency indicators for power drive systems and motor starters
Note: GB/T 12668.902-2021, Adjustable speed electrical power drive systems - Part 9-2:Ecodesign for power drive systems, motor starters, power electronics and their driven applications - Energy efficiency indicators for power drive systems and motor starters (IEC61800-9-2:2017, IDT)
3 Terms, definitions, symbols and acronyms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60034-1, IEC 60034-30-1 and in IEC TS 60034-30-2 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
? IEC Electropedia: available at http://www.electropedia.org/
? ISO Online browsing platform: available at http://www.iso.org/obp
3.2 Symbols
The following symbols are applicable to this document.
?p is the differential pressure, Pa
ηhyd is the hydraulic efficiency, per unit
ηn is the nominal efficiency, %
ηN is the rated efficiency, %
F is the drag force, N
fe is the electrical frequency, Hz
fN is the rated electrical frequency, Hz
I is the RMS current, A
n is the actual speed, min -1
nN is the rated speed, min -1
nmax is the maximum speed, min -1
nS is the synchronous speed, min -1
p is the number of poles
Pmot is the motor output power, W
PN is the rated output power, W
Q is the flow rate, m 3 /s
R is the resistance, Ω
s is the slip of an induction motor, %
Tmax is the maximum output torque, Nm
TN is the rated output torque, Nm
UN is the rated voltage, V
v is the linear speed, m/s
3.3 Acronyms
The following acronyms are applicable to this document.
AC alternating current
CDM complete drive module
DC direct current
DOL direct-on-line
EM electric motor
EP extended product
ESOB end-suction own bearing
GHG greenhouse gas
IE international energy efficiency of component index
IES international energy efficiency of system index
LSPM line-start permanent magnet synchronous motor
MDU motor driven unit
OEM original equipment manufacturer
OP operating point
PDS power drive system
PMSM permanent magnet synchronous motor
PWM pulse width modulation
ROI return on investment
RMS root-mean-square
RSM reluctance synchronous motor
TC technical committee
THD total harmonic distortion
VFD variable frequency drive
4 Background
4.1 General
This clause introduces the importance of energy efficiency and the high energy saving potential related to the use of electric motors and variable frequency drives.
The global total amount of greenhouse gas emissions (GHG) was 49 gigatons (Gt) of CO2 equivalents in 2010. The energy sector, which primarily involves electricity and heat production, had the largest share of 35 % of the GHG emissions[1]. Coal was by far the largest energy source for electricity production in 2015, with a share of 43 % of the total global generation of 20000 TWh, followed by gas, hydro and nuclear with a share of 19 %, 15 % and 12 %, respectively[2]. The average efficiency rate of coal power plants in 2017 was 33 %[3].
As mentioned in the introduction, about 50 % of the total global electric energy consumption is converted by electric motors, which are the largest consumers of electricity per component type[4-5]. Industrial motors alone accounted for around 30 % of all electricity consumption in 2016, as seen in Figure 1 a)[4-6]. Another 20 % of electricity is consumed by electric motors in other sectors like commercial, residential, transport and agriculture[6]. Therefore, electric motors and especially motors operated by variable frequency drives (VFD) are key components for achieving immense electricity savings. The installed base of industrial low voltage motors in the power range between 0.12 kW and 1000 kW is estimated to be more than 750 million units[7].
Note: The most part of the electric energy consumed by electric motors is converted into mechanical energy to the driven equipment. The rest is converted into heat, that is losses. The expression “energy consumption” is used in this document as an alternative to “energy conversion”, since it is a commonly used expression even though the definition is according to the aforementioned sentence.
Currently, the share of motors equipped with electronic speed control is only about 12 % of the installed motor base, as illustrated in Figure 1 b)[8]. It is estimated that it would be beneficial for energy savings that this share should be more than 50 %. Replacing a direct on line motor with a new motor with a higher efficiency class is a simple measure to improve energy efficiency in most applications. However, a greater energy saving potential is associated with speed control, when this can be used to replace less efficient mechanical control equipment like throttle valves for pumps.
When taking life cycle costs into account, investments in energy saving measures can often pay off within just a few years, or even months. The cost of electricity accounts for up to 96 % of the total life cycle cost of a motor driven system, while the investment and installation costs only account for around 2.5 % and maintenance costs account for the remaining 1.5 %, as shown in Figure 1 c)[8].
