FEATURE DRIVES, CONTROLS & MOTORS


180 years in the making: unlocking the holy grail of motor efficiency


For many years, magnetic reluctance motors were typically overlooked in favour of induction or permanent magnet designs. Yet now, nearly two centuries since the invention of the first reluctance motor, the synchronous reluctance motor (SynRM) is unlocking ultra-premium IE5 efficiency levels. ABB UK managing director, David Hughes, explains


how we arrived at this point, and what it means for motor-driven applications both now and in the future


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eluctance motors have come a long way. The first switched reluctance motor was invented all the way back


in 1838 and was initially designed to propel locomotives. Unlike common brushed DC


motor types, in a switched reluctance motor power is delivered to windings in the stator rather than the rotor. The idea, however, was unfortunately doomed to failure – the motor was highly complex for its time and, rather


Smart SenSor Hub PreventS macHine Downtime


SICK has launched the compact sHub sensor hub, a smart add-on to its HIPERFACE DSL single-cable motor feedback system which turns servo motors into a source of data for real-time condition monitoring and predictive maintenance of machines. This fits as an extension to SICK EDS/EDM35 motor feedback encoders to send temperature,


vibration, position, and speed data via HIPERFACE DSL to the servo controller, assuring early detection of critical mechanical failures, such as ball bearing damage or motor imbalance. In common with all SICK HIPERFACE DSL encoders, the EDS/EDM35 incorporate a winding


temperature sensor input and have a service-life histogram inside them for condition monitoring. The sHub sensor hub adds a built-in vibration sensor and enables all data to be routed synchronously to the drive without the need for additional cabling. Darren Pratt, SICK UK Encoder product manager, said: “The sHub offers an attractive proposition


for machine builders who want to offer smart condition monitoring as a premium service, so that their customers can improve operating efficiency and machine uptime.” The addition of an integral vibration sensor in the SICK sHub sensor hub greatly simplifies data


analysis, making it much more straightforward to provide relevant information about motor condition, when compared with externally-mounted sensors. Because it sends vibration data synchronised with the position and speed of the motor via HIPERFACE DSL, a clear insight can be gained from inside the control loop. The sHub vibration sensor can measure up to 50g with a 10kHz bandwidth. The sHub and EDS/EDM35 smart motor


feedback system can also be integrated into drive safety systems, such as safely limited speed (SLS), thanks to the safe communication capability of HIPERFACE DSL.


SicK t: 01727 831121 54 DeSiGn SoLutionS JULY/AUGUST 2021


than utilising the power electronics that we have today, it relied on mechanical switches to energise the windings, which could not operate fast enough to generate anything more than very slow speeds. Then, in the 1920s, the synchronous


reluctance motor was invented. These use a specially designed cageless rotor, eliminating rotor losses. A magnetic field is generated inside the motor, which is guided through low reluctance paths. The field is rotated, which in turn pulls the rotor around to generate torque. The switched reluctance motor initially suffered from a lack of effective speed control. It was not until the 1970s, with the emergence


of fast-switching electronics within variable speed drives (VSDs), that the synchronous reluctance motor was able to finally come into its own and reach performances comparable to that of conventional induction and permanent magnet motors.


getting up to speed


Even then, the synchronous reluctance motor was still, for many years, widely considered uneconomical due to its complexity and cost. Furthermore, VSD technology had not yet evolved sufficiently to handle the complex needs of the motor, as the drive needed to be capable of switching the frequency of the supply current thousands of times per second to control the magnetic field effectively. It was only in the early 21st century that both the VSD and the synchronous reluctance motor had both developed to a point where they were finally able to effectively combine in successful operation together and deliver the required


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