PU20 - Wide-Range Railway Power Supply Unit, 24 to 110 VDC, 120 W

Designed for Rail Applications, Vehicle and Wayside

The PU20 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 rolling-stock and wayside use.

Wide-Range Input

The PU20 has a nominal input power range of 24 V DC to 110 V DC with a max. input voltage range of 14.4 V DC to 154 V DC (according to EN 50155 and S-9401). The PU20 has a configurable voltage range for 24, 36, 48, 74, 96, 110 V DC or wide input range, which is controlled by a rotary switch.

Advanced Power Supply Functionality

The standard output voltage is 12.6 V DC with a dynamic load sharing between 12.6 V DC and 5 V DC with 120 W. 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 PU20 also has a standby voltage of 5 V with 5 W to supply the independent shelf controller, and to support wake-on-LAN functionality. The standby voltage is always on.

The PSU provides an inhibit port for switching the output voltages. It also indicates the event of an input power failure, output voltage failure or an over temperature.

Rugged Design

The PSU is coated conformally, and all components are secured against vibration. When more power supplies run in parallel, there is a load sharing. The double voltage monitoring ensures that the output voltage is within the valid range. In case of error, the voltage is powered-down. The thermal stress is extremely low due to integrated heat sinks, and diversion of dissipated heat over the mounting surface.

The PU20 is compliant with EN 50155, meeting all shock, vibration, EMC and isolation requirements. It operates under temperatures from -40 °C to +70 °C with increments to +85 °C for 10 minutes, with a hold up time of 10 ms in accordance with EN 50155 Class 2.


  • 3U, 6 HP, 19" rack mountable
  • Wide range input 24 V DC to 110 V DC nominal
  • Configurable voltage range for 24, 36, 48, 74, 96 V DC
  • Output power 120 W without derating
  • Hold up time 10 ms (EN 50155 Class S2)
  • Active power sharing
  • Inverse current protection
  • H15 rear connector
  • -40 °C to +85 °C
  • Conformal coating
  • Input voltage according to S-9401
  • EN 50155 compliance