PU21 - Wide-Range Railway Power Supply Unit, 100 to 240 VAC, 120 W

Designed for Rail Applications, Vehicle and Wayside

The PU21 is a plug-in power supply unit for 19" systems (like VMEbus and CompactPCI Serial). It is especially designed for computer systems in public transport vehicles and for harsh environments, like railway applications, making it suitable for both onboard and wayside use.

Wide-Range Input

The PU21 has a nominal input power range of 100 to 240 VAC with a max. input voltage range of 90 to 264 VAC.

Advanced Power Supply Functionality

The output power is 120 W, with a dynamic load sharing of between 5 V and 12 V. The output power at 3.3 V is 30 W, which is shared with the 5 V load. Switch-on behavior is independent of the load.

The PU21 also has a standby voltage of 5 V with 5W to supply the independent shelf controller, and to support wake-on-LAN functionality.

The PSU provides three ports on the secondary side which indicate the event of an input power failure, output voltage failure or a fail-over temperature.

Rugged Design

The PSU is coated conformally, and all components are secured against vibration. When more power supplies run in parallel, the performance loss is shared evenly and, in case of a fault in one of the power supplies, the output power is removed completely so as to avoid any negative effects. The double power monitoring ensures that the output voltage is within the valid range. In case of error, the voltage is powered-down as prepared by the SIL applications. The thermal stress is extremely low due to integrated heat sinks, and diversion of dissipated heat over the mounting surface.

The PU21 is fully compliant with EN 50155, meeting all shock, vibration, EMC and isolation requirements. Operating under temperatures ranging from -40 to 70°C with increments to 85°C for 10 minutes, with a hold up time of 20 ms (at an input of 100 V).


  • 3U, 6 HP, 19" rack mountable
  • Input voltage range of 100 to 240 VAC
  • Output power 120 W without derating
  • Holdup time 20 ms
  • Active power sharing
  • Inverse current protection
  • Redundant output voltage monitoring
  • H15 rear connector
  • -40°C to +85°C
  • Conformal coating
  • Fully EN 50155 compliant