Efficiency clarifications: motors and VSDs

In September 2014, the Institution of Engineering and Technology (IET) responded to a request for comments regarding Lot 30 and highlighted some interesting points within the draft regulation.

The points that the IET picked up on were in regards to the unclear efficiency regulations concerning VSD and motor combinations. The difficulty in regulating the area stems from the flexibility of the modern general purpose VSDs.

Energy losses depend closely on operational settings. For example, if a VSD has a low switching frequency, losses would be much lower than practical operations settings. However, this is not taken into account by the current framework of the Ecodesign Directive.

A beneficial feature of the modern VSD is that functionality often spans beyond conventional motor control. Sequencing, process control, motion control and system control are associated with using more energy than an average VSD function. These are important elements of drive system design and energy loss from these should be excluded from maximum loss figures so as not to discourage designers.

The main problem is that efficiency cannot be effectively measured for motors that are specifically designed to operate only with a VSD. The IET recommends instead that these types of motors be specifically excluded from the regulations.

Furthermore, the IET commented that current regulations do not explicitly address the difficulty in calculating the overall efficiency of a motor operating in tandem with a VSD. Its recommendation is for a review of this combination in the next assessment process. The IET also highlights the increasing sales of VSDs for medium voltage motors (1-35kV) and recommends that this be taken into account in the next assessment process as well.

The final point raised, and one which European Automation agrees with unwaveringly, is that there needs to be more onus on the manufacturer to ensure access data for each model and build variant. Countless times clients are unsure about what part they need once a breakdown has occurred. Who can honestly say they are completely aware of the year of manufacture for every motor within their operation? But if things go wrong, you might well need to know and quickly.

Regardless of whether or not you're running a motor or VSD that is now obsolete thanks to the Ecodesign Directive, European Automation can find and replace those parts, sometimes in as little as 9 hours.

To learn more please visit www.euautomation.com.