U POWER NBDD - rotary diesel ups

The Hitzinger Rotary Diesel UPS system provides the optimum solution for mission critical applications that require a source of uninterruptable power supply. The NBDD system, with rigid steel flywheel energy storage device, provides guaranteed tolerances on the consumer with +/-5% frequency variation (See NBDK for +/-1% IT Grade Power). The NBDD system is the perfect solution for industrial applications, airport lighting systems, stadiums and other mission critical environments.

The Hitzinger Rotary Diesel UPS system is made up of four main components; The flywheel which is directly mounted to the alternator, the diesel engine and the coupling choke. During the stand-by operation, the system provides a reliable source of clean power and conditions the mains input to ensure; automatic power factor correction (0.98>unity), Harmonic suppression (<2% to Comply with G5/4) and Input load levelling irrespective of 100% unbalanced load. As an alternative to the traditional static UPS with battery energy store, the DRUPS provides an unrivalled level of reliability, with a MTBF of over 1,000,000+hrs.


During stand-by, the flywheel is accelerated to full speed (Also referred to as charged) and runs continuously together with the alternator to provide mains power conditioning. In-case of mains failure, the energy stored within the flywheel is used to maintain the speed of the alternator and provides a sufficient bridge until the diesel engine has accelerated to a speed of ~800rpm. At which point, the electromagnetic clutch will engage and the diesel engine will be brought up to synchronous speed to become the main drive of the alternator and provide guaranteed power for the longer duration.

Only when the flywheel has become fully charged and the mains is available, will the rotary Diesel UPS system synchronous back to the mains ready for another interruption.

Coupling Choke

The coupling choke connects the incoming grid with the UPS output supply. This setup provides conditioning of the the mains to within tolerance together with power factor correction and harmonic suppression.

The special design of the choke provides a high degree of de-coupling in both directions between the input and the output. The Coupling choke provides:

  • Supports static and dynamic voltage decoupling on the UPS collecting bar
  • Decouples fluctuations and harmonics on the grid
  • Upper harmonics filter
  • Balancing of dynamic loads
  • Restriction of current in case of short circuit

In the event of input short circuit the current flow towards the grid network is limited by the choke to < 200 % I nominal until the input is disconnected. During this transient the current feed back to the mains is wholly reactive, ensuring all the kinetic stored energy can be fully utilised for the critical load.

Technical data


  • Multiple turn-key solutions are available for the entire range of rotary diesel UPS products, including; external and internal setup, containerised or enclosed versions (Both of which can be tailored to suit the exact requirement)
  • Varies topologies including IP-Bus, Parallel Redundant, Isolated Redundant, Distributed redundant and many more available upon request
  • Redundancy variants (system-/controller-redundant,..)

Power classes

  • All of the versions are available in Power ratings from 100kVA to 2500kVA, together with Voltages from 400V to 15kV and Frequencies of 50Hz/60Hz.
  • Utilisation of the autonomous time for maximum temporary bridging


  • Noise levels as low as 55dB @1m are available for all versions using appropriately sized attenuation
  • The standard Ambient temperature range is -30°C to +50°C

If you require a Technical Specification, please send us an Email (Contact Us) detailing your requirements. and we can can send the appropriate documents for your review


  • IEC 60034-1
  • IEC / EN 88528-11
  • ÖVE/ÖNORM 8001
  • ÖVE/ÖNORM 8002
  • ÖVE/ÖNORM 8007
  • ISO 3046
  • CAT I, CAT II of the International Civil Aviation Organization (ICAO)
  • Other standards (e.g. UIC, EN, IEC, ISO, UL) to requirements

Technical highlights

  • Hitzinger are both manufactures and designers of rotating electrical equipment, providing turn-key solution to suit your exact requirements. Our experience in turn-key solutions, means we can provide complete project management; from detailed design to installation and commissioning.
  • Efficiency-optimised version with up to 97 % for lowest running costs and lowest total cost of ownership (TCO) with respect to system service life.
  • Using a Electromagnetic Clutch, the Hitzinger Rotary Diesel UPS systems can provide a guaranteed redundant start-up. In the worst case scenario where the starter batteries fail or the starter is defective, a back-up solution brings the engine up to speed and the system continues to guarantee an uninterrupted supply to critical consumers.
  • Preventive system protection for prolonged service life, system monitoring, coil temperature monitoring, vibration monitoring, etc.
  • A wide range of power is available from a single unit (>1000kVA) and direct generation 11kV also available to mitigate losses from step-transformers
  • Automatic re-greasing of inner bearings maximise product life and ensure minimal maintenance requirements and downtime.
  • Network stabilisation and filtering to protect consumers from harmonic oscillations, voltage peaks, voltage drops and frequency faults.
  • All Hitzinger DRUPS systems are EMC-tested
  • Hitzinger's patented 15.4-inch touch panel with intuitive user menu navigation is provided as standard
  • In-case of a 'Black Start' scenario, the Rotary Diesel UPS systems can be put into operation using batteries or air starters, providing a black start facility