New Industry Products

Absopulse’s 1000VA Railway Inverters Operate Over a Range of DC Input Choices

May 07, 2021 by Gary Elinoff

Convection cooling is accomplished through a finned heat sinking element, with no forced heat required


The RSI 1K-HSA-F31 series operates over a range of DC input choices and provides either 115 or 230 VAC outputs

The RSI 1K-HSA-F31 series. Image courtesy of Absopulse
The RSI 1K-HSA-F31 series. Image courtesy of Absopulse


The members of RSI 1K-HSA-F31 series accomplish cooling solely by natural air convection. There is no requirement for the inverter to be attached to a heat sinking surface, nor for forced air. 

As depicted above, the unit sits on top of its own heatsink assembly block, part of its chassis. The cooling is achieved through the fins on the under-surface. Natural convection through the fin-slots provides still more cooling.

The heatsink assembly makes it possible to mount the inverters on uneven surfaces. The well-designed cooling regime also makes it possible to mount them on surfaces that are thermally non-conductive; these include brick walls and even plastic or wood.


DC inputs and AC Outputs:


  • 36Vdc (25–51V)
  • 48Vdc (33-67V)
  • 72Vdc (50-101V)
  • 96Vdc (67-135V)
  • 110Vdc (77-154V) 

There is also a version accepting a 24Vdc (17-34V)  input, but the output is derated to 750 VA


A 115 VAC output is available at either 60 or 400 Hz, as is a 230 VAC output at 50 Hz. The inverter’s neutral output is connected to the chassis. However, an isolated floating out is also available. 



The inverters sport 1500 VDC input/output isolation. They also offer thermal shutdown with automatic recovery if the condition improves sufficiently. Current limiting and short-circuit protection, as well as protection against reverse polarity, are also provided

There is also overvoltage protection that kicks in at 140 VAC for 115 VAC outputs, and at 280 VAC for 230 VAC systems.


Pure Sine Wave Inverters

RSI 1K-HSA-F31 series are pure sine wave converters, which simply means that their output is a pure AC sine wave. This isn’t an obvious point, because some inverters still generate modified sine waves. The differences are depicted below.

Pure sine wave vs modified sine wave. Image courtesy of altE
Pure sine wave vs modified sine wave. Image courtesy of altE


While modified sine waves may work OK with resistive heating devices and the like, they will obviously play havoc with modern electronic equipment.


Electrical Specifications

  • Typical efficiency at full load is 80%
  • Total harmonic distortion at full load is under 5%
  • Line/Load Regulation is ± 6% from no load to full load, with ± 2% is optionally available
  • Output noise over a 20 MHz bandwidth is under 500 millivolts RMS



  • Railway rolling stock
  • Trackside applications
  • Industrial quality versions enable deployment into industrial arenas


Physical Considerations

  • The members of the RSI 1K-HSA-F31 series operate over a -25 to +55℃ ambient temperature range with no derating.
  • The inverter and its attached HSA-F31 heatsink assembly together measure 22.5 x 5.9 x 14″.


Regulatory and Safety

  • EN50155 - electronic equipment used on railway rolling stock. 
  • EN50121-3-2 - EMI
  • EN61000-4-2 – ESD
  • EN61000-4-3 - RF Immunity
  • EN61000-4-4 - Fast Transients
  • EN61000-4-6 - Conducted Immunity
  • IEC 61373 Cat 1 A&B – Shock and vibration
  • C22.2 No. 107.1-01, UL 458 and EN/UL60950-1