FEATURE
DRIVES, CONTROLS & MOTORS
BRIDGING THE GAP BETWEEN STEPPER AND SERVO DRIVE
Festo has introduced a new range of
extra-low voltage servo drives.
Ben Lloyd, product manager – Electric
Automation, examines their benefits
W
hether to use a stepper or a servo drive can be a tricky decision for machine builders and design engineers. While the
high dynamics and controllability of servo control loops are useful in many automation applications, there are times when the pulse, lock and stay characteristics of a stepper are the better choice. The development of a new range of extra-low voltage servo drives means that this dilemma is now easily solved. These new extra-low voltage devices work at 24 or 48VDC. Capable of open or closed loop positioning, they effectively bridge the gap between stepper and servo drives. Several new features distinguish this new
generation of controllers from previous drives, offering multiple benefits for users.
BENEFITS OF THE NEW DRIVES Better performance Significant performance improvements have been achieved because the new servo drives are equipped with a microcontroller, which is three times more powerful than previous models. This delivers a number of performance enhancements, including: multi-protocol fieldbus compatibility, field weakening, energy management, auto-tuning, and U/f open loop control. It also features an integrated web server, an
advanced feature for a low-cost device. This enables the easy transfer of data to and from the servo drive for fast, simple set-up, diagnostics, and file transfers.
Improved communication Interoperability is another challenge that has been addressed. The new servo drives have the integral capability to communicate instantly to more than 75% of major fieldbus systems (including PROFINET, EtherCAT, EtherNet IP, and Modbus), either through simple DIP switch settings, software set-up, or auto-recognition. This eliminates the need for any changes to electrical designs, cabinet layout or wiring when swapping between control architectures – this saves time and reduces costs for special purpose machine builders adapting to end- user specifications. With fewer stocked or service parts required, and fewer parts for installers and service technicians to become familiar with, these devices streamline BoM and reduce training requirements.
Higher speeds Field weakening delivers another improvement, enabling the connected motors to achieve higher maximum speeds or torques. For example, at low torques the maximum speed increases from 1,600 to 2,300 rpm – an increase of 44%. This presents the opportunity to select a smaller, lower cost motor to perform the same task.
Cost reductions Compatibility with existing drive technologies is essential to offer designers and machine builders more cost-efficient solutions. Industrial automation manufacturers are therefore designing the new extra-low voltage models to share the same control integration and function blocks as standard servo drives. This offers opportunities for significant cost reductions by combining the two types of drives within one system.
Energy saving Connectivity for braking
30 DESIGN SOLUTIONS MARCH 2025
resistors enables efficient energy management, soaking up the energy spikes and increasing the drive’s peak performance characteristics. A further energy saving option is to use the DC link sharing energy peaks between different drives within a system. New servo drives are very compact but can typically manage an impressive nominal current of 8A and up to 20A peak for limited durations (a few seconds) for maximum acceleration or de-acceleration peaks within a positioning cycle. Extra-low voltage
servo drives are also very mechanically efficient packages, featuring advanced electronics within a robust enclosure with good EMC protection. An earthing fin shields the
encoder feedback cabling,
protecting the drive within ‘noisy’ environments on industrial machinery.
Simpler to size Free to access Electric Motion Sizing software facilitates selection of the correct motor/drive combination: with or without mechanical axis, using the manufacturer’s or third party guides, or a totally rotary application. Users simply input some key parameters and the software identifies the possible standard or extra-low voltage options within seconds, prioritised by cost. It also displays the servo drive and motor workloads to enable users to make an informed choice. Using a software sizing tool can therefore dramatically reduce design and build time, giving confidence that the correct drive has been selected for the task.
A BENEFICIAL SOLUTION With a list price of under £500 and free programming software, the new generation of low voltage servo drives has the potential to deliver big savings for machine builders and users. The provision of free sizing software also makes selection and programming much easier, enabling the user to tailor their chosen drive to the needs of the application and reap the benefits of both control formats. The ease with which the new drives can
be combined with standard models is particularly advantageous in applications where drives are currently over-specified, combatting the compatibility and control issues usually associated with mixing drives within a single control system.
Festo
www.festo.com/cmmt-st
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