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  • IEC 60034-31:2009

  • 33 –

Annex A Super-Premium Efficiency (IE4)


For information purposes the following proposed nominal limits of Super-Premium Efficiency are given. In 60034-30 the terms “Super-Premium” and “IE4” are projected as approximately 15% reduced losses compared to IE3. The exact definition is proposed in this Annex.

The IE4 energy-efficiency class is not limited to three-phase cage-induction motors like the classes IE1, IE2 and IE3 of IEC 60034-30. Instead, IE4 is intended to be used with all types of electrical motors, particularly with converter-fed machines (both cage-induction and other types like permanent-magnet synchronous-motors, etc.).

Since grid frequency and number of poles of converter-fed machines are not directly related to speed, these motors are typically rated for a speed range and classified by torque rather than power. Consequently the limits of IE4 are ranked by torque and given for discrete speed ranges.

NOTE Users should be aware that frequency converters also have an associated efficiency which will reduce the system efficiency (motor plus converter).

NOTE For efficiency determination of converter-fed motors see IEC 60034-2-3.

However, it is neither required to rate the motor for the entire speed range from 801 to 3600 1/min nor for a constant torque rating over the whole rated speed range.

The nominal limits of Super-Premium Efficiency may generally be computed for the rated

torque TN using the following formula:

T A N N = l o g 1 0 1 Nm η


T B N + l o g 1 1 Nm 0


T C N + N m 1 l o g 1 0

+ D

where A, B, C, D = interpolation coefficients (see table A.1 below).

NOTE The formula and interpolation coefficients were mathematically derived to create a best fitting curve for the desired nominal efficiency limits. They do not have a physical meaning.

The resulting efficiency (%) are rounded to the nearest tenth, i.e. xx,x%.

Nominal IE4-efficiencies for torques greater than 2000 Nm are equal to the limits for 2000 Nm. Nominal IE4-efficiencies for output powers greater than 400 kW are not defined.

When more than one torque and speed (ranges) are rated, the nominal efficiency limits according to this standard should be computed and applied individually for each combination of rated motor torque(s) and rated speed (ranges).

For motors rated by power PN rather than torque the following formula should be used to

determine TN:

= N T

N nN P

60 1000 2π

The resulting torque should be rounded to the nearest value from the R10 series of preferred numbers, see ISO 3.

In order to maintain compatibility with single-speed, line-operated 2-, 4- and 6-pole motors, table A.3 for torque and speed conversion to standard power levels is provided. On this basis table A.4 gives the nominal IE4-efficiency limits for 50 Hz power supply and table A.5 for 60 Hz power supply.

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