Freedom from supplier dependency Limiting supplier dependency is a fundamentally good idea for other reasons that delivery delays. In the lifetime of an application, no maintenance crew wants to be limited in finding replacement motors due to special and non-standard motor dimensions. Instead, the safe approach is to insist on specifying motors with standard IEC or NEMA dimensions right from the outset. In this way, it will always be possible to find a wealth of alternative motors, which physically fit the installation. New technologies pack more power into the same motor frame size. This means that the high-efficiency motor keeps the normative dimensions but is often one frame size smaller. Likewise, to win the greatest benefits in maintenance management, it is important to have specified from the outset that the AC drive connected to the motor possesses the compatibility to adapt to any standard motor technology. This quality is vital for painless motor interchange. Coping strategy for difficult locations A fast and easy motor retrofit, even in difficult environments, and awkward, inaccessible installation areas, also places special demands on the AC drive specification. Ideally, the drive must be able to comply with every installation environment. This compliance includes high temperature operability without derating, and superior ingress protection at the level of IP55/UL Type 12 or IP66/UL Type 4X, which enables you to mount the drive without a cabinet. Another useful quality is the ability to mount the drive decentrally in the area close to the motor. When decentral mounting is not possible, the best AC drives available in the market can be mounted with as much as 150 m motor cable length, and still deliver full EMC compliance. This facilitates flexible installation when, for various locational reasons, the drive cannot be installed close to the motor. Furthermore, due to the flexibility in motor technology, the most adaptable of the drives available on the market support you with far more than just increasing the motor efficiency. They also open the door to using motor technologies that come in smaller motor frame sizes, when this is acceptable in an exchange situation – which truly opens up new horizons for solving the awkward installation challenge. What choice do I even have? Motor technology has stood still for decades, until recently. Ten to fifteen years ago, there was really only one type of electrical motor used in industrial applications, and this was the induction machine (IM). However, the energy efficiency discussion in the new millennium has pushed the development of new motor technologies and the reinvention of existing, older technologies, with up to one hundred years history behind them. Because the industrial world now has variable speed drives at its disposal, the older technologies can now be optimized for energy efficiency. For example, synchronous reluctance motor technology, first invented a century ago, was originally optimized for size and torque. Nowadays the high-efficiency synchronous reluctance motor (SynRM) has emerged, which is instead optimized for energy efficiency. Each motor type has its advantages - and drawbacks Each motor type has its advantages and drawbacks. For example, optimization of the induction machine (IM) to improve its energy efficiency (that is, to improve its IE rating) can result in an increase in physical dimensions. As outlined before in retrofit situations, its size and weight can become problematic. When comparatively assessing the advantages of different motor technologies, remember: • IE class is not a characteristic of a particular technology. For example, you can choose SynRM motors of IE2 or IE4. • Technologies differ in the way that they behave under part loads. A motor using one particular technology is not intrinsically more efficient than a motor based on another technology. It depends on the application. • Different motor technologies influence the inrush currents. Sometimes new circuit breakers are required when changing motor type and not using variable speed drives. • Designers need to consider the cos phi/power factor of the selected motor technology when dimensioning the drive. This may result in having to over-dimension the drive. Despite the higher initial cost, the return on investment may still be attractive due to the lower energy consumption. Technologies like SynRM require a different sizing of the drive. For SynRM, the lower cos phi/power factor often results in the need to over-size the drive 2 What’s in it for you, when it comes to motor independence?
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