The National Library of France (BnF) looked to source the drive systems from a single supplier capable of offering expertise and value-added service. The BnF’s collections are unique throughout the world, comprising fourteen million books and periodicals, but also manuscripts, prints, photographs, maps and charts, musical scores, coins, medals, sound archives, videos, multimedia, stage sets, costumes and much more. And they’re growing constantly.
The library is home to a vast documentary heritage encompassing all disciplines, whether intellectual, artistic or scientific. Its physical spaces are frequented each year by more than one million visitors, and its digital library, Gallica, provides free access to more than three million documents.
An extremely reliable air conditioning system
To protect these treasures and welcome its many visitors, the BnF was acutely aware of the need to maintain an extremely reliable air conditioning system. With this in mind, an initial project was defined: to replace an asynchronous variable speed drive assembly with a new drive system that would be used to power an air conditioning pump, itself responsible for half of the library’s reading rooms.
«The results of an energy optimisation study revealed in particular that the application’s operating efficiency fell to just 50% in the winter. The ROI calculation showed that it would make far more sense to swap the asynchronous drive system for the Dyneo® high-performance synchronous technology from Leroy-Somer», explains Jérôme Hardy from GED ADREM, a partner company of the Leroy-Somer service network.
To handle the variable torque load (also referred to as the quadratic torque) of the pump and ventilation applications, Emerson implemented a solution comprising a Leroy-Somer Dyneo LSRPM 250 (85 kW) motor and a Control Techniques Unidrive M600 variable speed drive unit.
The permanent magnet synchronous motor is perfectly suited to applications of this kind, offering enhanced efficiency of up to 96% over the whole operating speed range. Another advantage, in terms of cost, comes from the sensorless control. This function, integrated into the Unidrive M drive unit, simulates an encoder input with a high degree of precision.
«With this solution, not only do we eliminate the cost of the encoder, but we also reduce the number of components and thus the probability of a breakdown», added Jérôme Hardy.
The BnF gave top priority to the service life and availability of the equipment. It commissioned Leroy-Somer as the sole supplier on the strength of its ability to guarantee operational reliability, including a performance warranty and the full interoperational compatibility of the components. A global approach was adopted with the consistent aim of maximising reliability:
«We applied Leroy-Somer’s premium service centre procedure. This extremely rigorous method uses multiple control points during installation and start-up. Operations such as alignment control, dielectric measurements and phase balancing offer real benefits in terms of both reliability and power consumption», adds Jérôme Hardy.
Since then, the equipment has been monitored, particularly by means of vibratory analysis, and the resulting data compared with the data collected during commissioning. This makes it easier to detect drift, premature wear and overconsumption.
The original motors, also from Leroy-Somer, were overhauled and kept as backup. The assembly is connected to the BMS (building management system), an automated, centralised supervision system that gives the speed setpoint. The next phase will involve conducting an energy efficiency study on the central air treatment systems and replacing the drive solution. Further system modernisation measures are also envisaged over the coming years.