SIEMENS
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Siemens D 35 · 2017
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System overview
Energy efficiency classes in accordance with EN 50598
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Overview
Step by step to more efficiency
One of the core objectives of the European Union is a sustain-
able power industry. In industrial plants today, around 70 % of
the power demand is from electrically driven systems. This high
percentage contains huge potential for saving energy in electri-
cal drives. For that reason, the European Union introduced
minimum requirements for the energy efficiency of electric mo-
tors in the form of a statutory motor regulation as early as 2011.
However, measures aimed solely at the motor are not enough to
achieve the mandatory energy-saving targets. The European
legislation fills this gap with the standard series EN 50598 and
extends the focus from individual drive components to entire
drive systems, even enabling consideration of specific use
cases.
The European standard series EN 50598 defines the ecodesign
requirements for drive systems in the low-voltage range with an
electrically driven machine. It consists of definitions for energy
efficiency (parts 1 and 2) and an ecobalance calculation
(part 3).
To take account of the different use cases, consideration of eight
application-relevant operating points has been introduced as
mandatory for the first time. Determination of loss values at these
eight points and definition of efficiency classes are laid down by
the standard in a uniform way. This enables data relevant to
operation, such as application-specific load profiles, to now be
taken into account more easily in the energy efficiency analysis.
The standard is especially important for variable-speed drives of
the following types:
•
for AC/AC converters without energy recovery functionality
•
for motors with integrated converters
•
for supply voltages of 100 V to 1000 V
•
for power ratings of 0.12 kW to 1000 kW
To cover all applications of driven machines, the new standard
defines operating points in full-load and partial-load operation,
at which the losses of the motor and drive systems have to be
determined. Based on the loss data at the operating points in
partial-load operation, variable-speed drives can be explicitly
considered in more detail. This makes their advantages espe-
cially clear.
Duty cycles for different driven machines
Moreover, frequency converters and motor systems are classi-
fied in efficiency classes, which permit an initial rough estimate
of the potential saving. Definition of reference systems is a key
aspect of this because they provide standard reference values.
The positioning of these reference systems defines the efficiency
class. The relative distance from the reference system can be
used as an absolute measure of the efficiency at the operating
point in question.
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Relative
torque
Relative speed
Load torque M = constant
Relative
torque
Relative speed
Load torque M ~ 1/n
Relative
torque
Relative speed
G_D011_EN_00467
Winders, coilers
Hoisting gear, extruders,
conveyor belts
Load torque M ~ n
2
Centrifugal pumps, fans
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© Siemens AG 2017