600 800

RFK/S series is available on the railway market (rolling stock) since 2002. In the last 15 years more than 40,000 resistors have been installed worldwide on trains, high speed trains, trams, EMU, Metro, APM, LRV, LTV, Trolley bus, for a total of more than 700 Millions of hours.

RFK/S series is used in the power traction converters or auxiliary converters with the following functions: charging / discharge of capacitors, over-voltage protection, earthing resistor, crowbar, damping resistor.

RFK/S is made of 2 windings on a mica sheet coated by inorganic cement or silicon resin, filled by quartzite sand and sealed by resin. The active element is insulated to the case thanks to creepage distance and mica sheets and ceramics. The construction is made with a poka-yoke system to avoid manufacturing mistakes. The aluminum case is anodized to prevent oxidation. Wire is made of NiCr alloy with thermal coefficient between 60 ppm (NiCr8020) and 240 ppm (NiCr3020).

RFK/S complies with the standards of Railway traction field: EN 50124-1, IEC 62497-1, EN 60077-1; EN 60322; EN 61373; EN 60068-2-11; EN 44545- 2 and Reach regulation.


The resistor is marked on the aluminum case with laser printing that assures very high contrast for the whole life of the component and it is indelible.
The following data are printed (example):
FAIRFILD ITALY WW/YY RFK/S 600 R = 10 Ω ± 5% UNM = 1.8 kV
WW/YY stands for Week Year, it is the batch number.


Warning: When mounted in the vertical orientation, the terminals must not be positioned at the top.
The unit must be fixed with 2 screws M6 with tightening torque of 8 Nm.
A minimum of 150 mm of free space must be provided in all directions around the resistor. Different installation conditions can be agreed with Fairfild technical office.


The resistor is packed in a way to prevent incidental damages due to transport. To avoid damage do not handle by cables. Upon customer’s request Fairfild can pack the resistors individually.


Every effort has been made to ensure that the information in this datasheet is accurate. Fairfild is not responsible for printing or clerical errors. All properties and characteristics mentioned in this datasheet are only for informational purposes. The information in this datasheet is offered solely for your consideration and should not be taken as a warranty or representation for which we assume legal responsibility. The customer bears all responsibility for use and application of Fairfild products. There is no responsibility of the manufacturer for any damage to persons and properties in case of improper use. Fairfild reserves the right to change specifications without prior notice.

Aesthetic imperfections

Fairfild is committed to assure the best appearance of the resistor case. In consideration of the multiple steps in the production manufacturing and handling from the extrusion of the aluminum profile to the packing of the resistor, some small imperfections may be present on the aluminum case. Fairfild established and applies a procedure to assess aesthetic defects. This procedure is available for the customer upon request.

Behavior in humid environment

RFK/S is designed to withstand critical and severe environmental conditions for 30 years.
The customer should communicate to Fairfild if the units are installed externally (both on the roof or under the body).
The value of the insulation resistance and the leakage current of the dielectric withstand test depend on the quantity of humidity inside and where it is more concentrated. Thanks to the correct designing of creepage and the use of right insulation materials we can assure electrical insulation for the life of the component.
At the end of the manufacturing process, before final check and packing, there is the process of the de-humidification whose aim is to expel the humidity out of the case. Thanks to this step, the insulation resistance of the brand-new resistors is extremely high. From the moment of the shipment to the entering in function of the rolling stock on which the resistor is installed, many months can pass. Depending on how the resistor is stored during this time, some humidity may enter into the case. The reason why this happen is due to the physical phenomenon of capillarity: the two systems (case and ambient) want to reach thermal and moisture equilibrium. When the ambient is humid and the resistor inside is dry, the humidity will penetrate through the little gaps between case and plug and resin and through the cable. The sealing construction takes into account that the hot air must be expelled when the resistor is supplied, because the air inside will expand its volume due to its thermal expansion. The direct consequence of this construction is that the quantity of humidity inside the case is not constant during the life of the component, and it is not homogenously spread in the inner volume. For this reason, Fairfild made tests in climatic chamber and rain test to define a minimum value of insulation resistance and dielectric withstand that is compliant with the use of the component on the rolling stock.


This datasheet is subject to copyright. Fairfild reserves all rights of translation in any language, reprinting, re-use of illustrations.
No part of this publication may be reproduced or transmitted in any form or by any means, electronic, mechanical, photocopying, without the written permission of the copyrighted owner Fairfild, Italy. Violations may be subject to legal proceedings involving monetary damages as well as compensation for costs and legal fees under Italian copyright law and regulation within the European Union.

Ordering information

Please specify the following when ordering:
• Model: 600 or 800
• Version: A or B
• Installation: indoor or outdoor
• Ohmic value at room temperature (standard tolerance ± 5%)
• Cable withstand voltage:1.8/3 kV or 3.6/6 kV
• Cable withstand temperature: 120 °C (tinned) or 150 °C (not tinned)
• Cable cross section: 2.5 mm2 or 4 mm2 or 6 mm2
• Cable length: 500 mm, 1000 mm; 2000 mm