9 Introduction and shall give an insight of the possibilities only. This book will focus on speed control of electrical motors by FC’s. 0.4 Frequency Converters Modern Frequency Converters can be applied to adjust and maintain the speed or torque of a driven machine with an accuracy within ±0.5%. This is independent of the load when compared to fi xed speed operation of the induction motor, where the speed can vary by as much as 3 – 5% (slip) from no-load to full-load operation. Motor manufacturers employ a variety of concepts to achieve high effi ciency in electrical motors.
For users it can be diffi cult to see the main benefi t from one technology to another, but the user will surely observe that energy effi cient motors need high technology controls. In principle, nearly all motors can be operated with control algorithms specially adapted to each motor type. Some manufacturers of FC’s relate their design to a narrow group of motor technologies, but many manufacturers have the diff erent algorithms built-in and selectable during commissioning. For the commissioner it is important that the FC is easy to commission based on data, normally available for the motor type which is used.
After commissioning the user must be confi dent that the system is really as easy as expected, thus online measurements of actual energy consumption and easy access to important data about the operation is essential. To ease the selection and ensure the various Government aims of reduction of energy consumption, there is a big motivation for a complete set of regulations. It must be borne in mind that all system components are important for potential energy savings.
According to the German Association of Electrical and Electronics Manufacturers (ZVEI), approximately 10% of the savings can be achieved by using high-effi ciency motors, 30% of the savings are achieved by variable speed, but as much as 60% of the potential savings are achieved by looking at the overall system and optimising accordingly. With that in mind, please read all chapters in this book and remember you cannot judge a system by looking at only one or few of the components involved. We wish you an interesting read.