^{First published in Pumps & Systems magazine}

For example, because direct drive motors are synchronous, there is no motor nominal slip, which improves the control accuracy. The motor also offers a lower speed range (200-600 rpm), yet higher torque at those low speeds, helping improve control. In addition, the absence of a gearbox and other mechanical drive components dramatically reduces space and maintenance requirements, leading to more efficient operations.

Coupling the drive directly to the paper machine with permanent magnet technology (i.e direct drive) has a positive impact on reducing power consumption. Importantly, the high energy losses typically associated with gearboxes are eliminated. Furthermore, permanent magnet technology means that none of the stator current is required to magnetize the rotor, so it is a more electrically efficient solution resulting in reduced electricity consumption.

Taking into account improved electrical efficiency and elimination some of the drive mechanics, direct drive systems offer efficiency savings of up to five percent over standard induction motors, which over 20 to 30 years is substantial.

Direct drive motors can reach very high horsepower at low voltage. This is well demonstrated with ABB’s patented Direct Torque Control (DTC), which enables the production of high torque at low speeds. In addition, no pulse encoders are required to operate ABB Direct Drive systems, and synchronous motors offer accurate speed control at the drive for better machine operation at low speeds.

ABB’s Direct Drive solutions differentiates themselves from other permanent magnet motor manufacturers in terms of efficiency and the horsepower range they are designed to support. ABB solutions go up to 3,000 HP, while others manage only a few hundred in paper applications.

Gearboxes are not known for their reliability past 20 years. And to achieve that, they require regular lubrication and mechanical maintenance, whereas direct drive motors – by eliminating gearboxes – can expect a greatly extended bearing life (ABB bearing solutions typically last up to 200,000 hours or 23 years). By providing a system that is reliable from the outset, users can be sure that it will remain reliable two decades or more down the road.

AC permanent magnet motors have proven high performance and flexibility at 200–600 rpm and are reliable due to fewer moving parts. Lower motor rotating speeds help boost production as they allow essential sections of the process to run slower and with more accuracy. Furthermore, pulse encoders increase complexity and provide more opportunities for failure whereas ABB’s patented DTC solutions remove the need for pulse encoders, which improves reliability.

Direct drives provide technology at higher efficiency by eliminating gearboxes. This means fewer components and simpler configurations, easier installation, and more efficient use of mill floor space. More importantly, it eliminates the maintenance safety concerns associated with gearboxes.

Eliminating a gearbox and removing the mechanical gears and pulse encoders reduces both the machine backside footprint and the engineering hours required to install and commission the drive.

For ABB, the focus is also on creating optimal dimensioning and configuration by looking at the efficiency of all components working together as a whole. This ensures the proper matching of drives and motors with process demands and also provides long-term cost reduction by engineering an energy-efficient system that helps minimize energy losses.

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A modular, direct drive system means the drives are extremely compact, yet all the parts are easily accessible, and the parts count is minimal.

This not only reduces interruption to production for planned and unplanned maintenance, but also decreases spare part inventories.

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Looking forward to the future of direct drive and permanent magnet motor technology, ABB is looking at developing even more compact solutions in the form of axial flux motors, a variant of permanent magnet motor technology that has found traction in applications outside the paper industry, including in elevators.

For now, direct drive technology remains a hugely beneficial opportunity for pulp and paper makers to realize increased productivity and energy savings.

There have also been advancements for drives in general from a digital side, most recently with the release of Winder Performance Optimization, an ABB Ability™ offering. The digital solution enables the full capacity of the motors, drives and supply to be utilized, in a short time, to maximize winder capacity.