Benefit from system efficiency and reduce energy

The IEC 61800-9 series of standards sets new benchmarks for evaluating environmentally friendly designs of drive systems and driven equipment.

Part 1 defines general requirements for the procedure and creation of standards for analyzing the energy efficiency of adjustable-speed electrical drives and their drive components. This part of IEC 61800-9 also serves as the basis for product-specific standards and describes the extended product range approach..

Part 2 of IEC 61800-9 is the most important for us as a system supplier of drive and automation technology. This part puts the guidelines defined in Part 1 into practice. Methods for determining the losses of an entire drive system (PDS: Power Drive System) and of frequency inverters (CDM: Complete Drive Module) are supplemented with the definition of efficiency classes for PDS and CDM in a power range from 0.12 to 1,000 kW.

Another new feature is that now, not only the motor's energy properties, but also those of the frequency inverters and the system composed of both elements, are analyzed and classified. The standard also accounts for the fact that drives are often operated outside of their nominal operating point. Every application is characterized by a load profile, meaning that it directly affects the capacity utilization of the drive system. EIEC 61800-9 partly covers this aspect. It defines eight load points at different speed and torque loads to allow the energy efficiency to be evaluated even in the partial load range.

The usual IE classes are available for evaluating the energy efficiency of asynchronous AC motors. The IE1 to IE4 classes defined in the international IEC 60034-30-1 standard provide information about the efficiency of the motor at its nominal operating point. This allows simple classification of the motor's energy efficiency, but does not provide information about its properties in the partial load range.

The IEC 61800-9-2 international standard now also allows power losses to be specified for the partial load range and compared to a defined reference motor of class IE2. In addition, the power losses of the motor and frequency inverter can be combined to calculate the total power loss of a drive system at all operating points.

However, this does not change the IE class determined for the motor. This class will still be determined by the efficiency at the nominal operating point.

Different legal requirements for the minimum efficiency of asynchronous motors exist worldwide. Our IE Guide web application offers you useful information on this subject. The energy efficiency tools with useful information can be accessed via "Engineering & selection" in the Online Support section.

Go to our Energyefficiency-Tools in our Online Support

In order to enable assessment of the energy efficiency of frequency inverters (CDM) in the future, IEC 61800-9-2 has defined IE classes for devices in a power range from 0.12 to 1,000 kW for the first time. Unlike for motors, the efficiency class of frequency inverters is not determined based on their efficiency as a percentage, but rather on the relative losses of the CDM in reference to its rated apparent output power. In order to avoid the effects of overmodulation, the evaluation is made at 90 % of the output voltage and 100 % of the torque-generating current. The relative losses are compared to what is known as a reference CDM in class IE1. If the relative losses of the CDM analyzed are at least 25 % below those of the reference CDM, class IE2 is achieved. If they are more than 25 % above it, only class IE0 is achieved.

Specifying the losses of a CDM at the other operating points allows them to be combined with the motor's losses to determine the total power loss of the drive system.

Unlike for asynchronous motors, there are not currently any legal requirements for compliance with a certain efficiency class. In Europe, a ban on frequency inverters that do not achieve class IE1 is already being discussed.

The overarching goal of IEC 61800-9-2 is to allow evaluation and comparison of the energy properties of drive systems consisting of a motor and frequency inverter in the power range from 0.12 to 1,000 kW.

This is why the IES0, IES1 and IES2 efficiency classes have been introduced for identification that focuses on the entire drive system. If the losses of the motor and frequency inverter at the nominal operating point are added up, the result is the losses of the PDS at this point. If you set this value in relation to the nominal power, you get the relative losses for the system. These losses can then be compared to a value defined in the standard for a reference PDS.

The reference PDS is defined with system efficiency class IES1. If the relative losses of the PDS analyzed are at least 20 % below those of the reference PDS, class IE2 is achieved. If they are more than 20 % above it, the PDS receives the IES0 classification.

Particularly for a PDS, consideration of the other load points defined in the standard is relevant. If the losses of the individual components are also added up at other points, manufacturers and operators of systems can use them to calculate the energy consumption of the drive systems in their applications.

This is particularly simple and efficient if the motor and CDM are purchased from a system supplier like SEW‑EURODRIVE. We are ready for the new system efficiency class, and can offer you both components, ideally coordinated with each other – high system efficiency included.

In the field of decentralized drive technology, we recommend integrated drive systems (PDS) such as our proven MOVIMOT^®. MOVIMOT^® combines an AC motor and a frequency inverter in a single unit and, with motor type DRE.. (IE2), already meets the requirements of the highest system efficiency class, IES2. However, SEW‑EURODRIVE also already offers MOVIMOT® with IE3 and IE4 motors of types DRN.. and DRU.. as standard – worldwide, of course.

For MOVIMOT^® with a motor of type DRE.., SEW‑EURODRIVE can already specify not only the system efficiency class, but also the losses at other operating points.
If you want to use MOVIMOT^® in a materials handling application, for example, you can determine the losses throughout the entire relevant load range.
With full capacity utilization of the drive system, the power losses at 100 % of the nominal torque and throughout the entire speed range are relevant. If you use a MOVIMOT^® with nominal power of 0.75 kW (DRE80M4 MM07), the losses in this example at a constant torque would be between 158 W and 237 W depending on the speed, meaning that they are considerably below the reference values defined in EN 50598-2.

Upon request, we can also provide information on the power losses for other MOVIMOT^®.

With the highly efficient MOVIGEAR^® mechatronic drive system, SEW-EURODRIVE is already one step ahead. The integration of motor, frequency inverter and gear unit, which has not so far been specified by a standard, is already minimizing losses and increasing the efficiency of systems.