Energy efficiency is one of the hottest topics of discussion in modern industry and society. Climate change, Carbon Dioxide emissions and environmental considerations in general are key drivers for this discussion. Also the goal of profitable business in a time of ever-increasing energy prices continues to fuel the debate. The European Union has taken an active role in creating unified requirements and standards looking to improve the energy efficiency of motor driven systems in industrial and everyday applications.
LOOKING AT THE BIGGER PICTURE
Standard induction motors alone use approximately 30% of all the electricity generated in the world. This explains why motors and the systems they drive are so crucial when discussing energy savings. In accordance with the Ecodesign Directive set in place back in 2009, individual motors are already required to be at least class IE2. The new standards look beyond just the motor, bringing entire motor driven systems within the scope of the directive.
The ultimate goal of the standard is to enable calculating the Energy Efficiency Index (EEI) for any given system. This means taking into account the motor and AC drive as well as the characteristics of the driven machine. The new standard gives the user or designer of any motor driven process the ability to identify areas of potential energy loss and select the optimum Power Drive System (PDS) to create the most energy efficient overall outcome across the entire system life cycle.
MINIMIZING LOSSES WITH AC DRIVES
The basic approach is the so-called extended product approach (EPA) – where the AC drive, motor and driven machine are considered as one unit. AC drives play a key role in minimizing losses in the overall process by offering speed control for applications and processes where the output must be controlled under changing requirements, thus improving the EEI of the overall system. The energy losses in AC drives are almost negligible, but the potential for overall savings by matching motor speed to load requirements is staggering.
AIMING FOR ZERO LOSSES
Imagine an ideal system with no losses. The lower the Energy Efficiency Index, the more efficient the driven system is. In defin- ing the overall EEI, two things are considered – the system losses at various working points and the time the system operates
at these working points. In order to be able to calculate the total system losses EN 50598 defines that the losses of the AC drive and motor have to be specified at eight different working points. Vacon provides the losses at the 8 points of reference required for the EEI calculation for all of its AC drives. Values in between can be found using linear interpolation or by simply using the closest maximum loss value. The (0;0) point can be added as a measure of the standby losses of the system. The installation of an optimized and carefully selected AC drive is often the most effective way to improve EEI.
WIPE AWAY THE LOSSES
The EEI classification schemes will be developed by the standard bodies responsible for each application – pumps, fans, compressors etc. starting in 2015. But before any official EEI standards and regulations are in place, we already offer you a unique window into monitoring energy efficiency. Every AC drive we deliver is equipped with this window. The control panel of each drive already lets you monitor and optimize your energy usage with a clear and simple MWh Counter. This feature is designed to let you wipe away losses and achieve the improved energy efficiency you are striving towards.
WELCOMING IE CLASSIFICATION TO THE AC DRIVES WORLD
Motor losses will continue to be defined by IE classes, as defined by IEC 60034-30, with an added (proposed) digit to specify the added losses caused by the switching frequency. The new EN 50598 -2 standard defines a similar classification scheme for the Basic Drive Module (BDM = AC Drive) in order to assist in choosing the best possible system. The minimum class accepted will be IE1. All of Vacon’s AC drives comfortably exceed the requirements for IE2 class, the lowest loss category currently defined.