here are a number of aspects to consider when replacing an electric motor, but installing the best you can afford is not the simplest solution. For a start, new higher IE efficiency standards might be
in place, eliminating the like-for-like replacement option. Added to this, change of machine operational functions might benefit from variable speed performance instead of single speed. Switching from an asynchronous motor type to a synchronous motor with a drive could offer greater efficiency and flexibility. For example, a 20% reduction in speed could achieve a 50% reduction in the energy used. In addition, a smaller, lighter, permanent magnet motor would give beneficial overall performance and weight savings, but it may introduce a requirement to adjust installation.
With 3-phase asynchronous motors, the principle determining factors after power, speed and mounting are size, weight and efficiency. If none of these are
an issue, then an IE3 compliant similar machine is a sound option. If they are a concern, however, then permanent magnet options should be explored, because in addition to satisfying all the above requirements they can, in some instances, reduce both weight and frame size by up to 50%.
Lafert’s HP Combi range
In this situation, it could be the ideal opportunity to review the duties of the machine in question and re-evaluate its performance and capabilities. Factors in this equation might include more precise speed (variable/constant) and/or position control, weight and, increasingly important, efficiency. If this is the case, there are various options to choose from with different
configurations and levels of sophistication, but all offer significant gains in greater efficiency. In many instances options can exceed current efficiency requirements right up to IE4 and IE5, giving a degree of future-proofing. Further, their torque and high efficiency can be delivered across a wide speed range. So, they offer performance characteristics suitable for both variable torque/speed duties and constant torque applications. All synchronous permanent magnet motors require an inverter to
operate, to start and control operation. The configuration of these types of motor/drive packages comprise a motor and any standard compatible drive, a motor with a drive optimised to run the motor, and a fully integrated motor and drive supplied as an integrated single unit. When the motor and drive are designed as a package, they typically
provide a plug-and-play solution, facilitating set-up and enabling systems to get up and running quickly, whilst permitting fine tuning for maximum system performance and optimised protection of the motor with one supplier for any support requirements. Another potential option is a fully integrated package of motor and
drive supplied as a single unit. It offers all the same performance benefits of the permanent magnet motor (high efficiency and compact size) and optimised drive, plus the advantages of reduced space requirement and no cable connections. Consequently, EMC concerns and tricky cable runs between the drive and motor are eliminated.
Where single phase motors are involved, there is now the matter of efficiency compliance. From July 2023 single phase asynchronous motors must, in most cases, comply with IE2. Consequently, a simple straight replacement might not be an option, no matter whether it is a PSC or CSR design.
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