VLT drive already compliant with EN 50598 standard
The Danfoss VLT frequency converter series already complies with the strictest requirements of the EN 50598 standard.
This means that VLT frequency converters are classified as IE2 – the highest efficiency class. Of course, the efficiency measure includes the losses in built-in RFI filters and DC chokes.
When the VLT feeds a good IE2 motor or IE3/IE4 motor, then the system will achieve the highest IES class: IES2.
Efficiency requirements for frequency converters - EN 50598
Guidelines for assessing the efficiency of frequency converters are defined in the EN 50598 standard. The standard is organised into several parts.
EN 50598-1: Extended Product Approach (EPA) – defines integration of the frequency converter and motor into an “extended product”, for example, a pump.
EN 50598-2: Energy Efficiency Indicators – defines efficiency classes.
•Classes IE0 – IE2 for frequency converters
•Classes IES0 – IES2 for power drive systems (frequency converter + motor).
The EN 50598-2 standard defines the efficiency classes IE0 – IE2 for frequency converters. The IE1 class represents the reference “state of the art”. If a frequency converter has 25% greater losses than the reference value of IE1 then it will be classified as IE0. If a frequency converter has 25% lower losses than the reference value of IE1 then it will be classified as IE2.
Scope of EN 50598 standard
The EN 50598 standard applies to frequency converters meeting the following criteria:
•Power rating range 0.12 kW – 1000 kW
•Voltage range 100 V – 1000 V, single axis AC/AC
•Drive systems for low voltage with asynchronous motors
Frequency converters with active front end are out of scope for the classification. These frequency converters typically display higher losses.
In Europe, minimum efficiency performance standards (MEPS) are expected at the IE1 level, in 2018.
Comparability is good. The IE classification is defined for a well-defined load, power factor and current. This enables an easy comparison of frequency converters based on efficiency classes.
EN 50598-2 IE classes for frequency converters
•EN 50598 uses the term “complete drive module” (CDM) to define the frequency converter.
•The IE class is defined at an operating point of 90% relative stator frequency and 100% load.
•Special test settings are not allowed. The frequency converter uses factory settings.
•The classification for the frequency converter includes integrated options such as EMC filters.