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RFK 250

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RFK 250

Wire wound on mica plate coated with cement filled with quarzite sand and sealed with aluminum plug

The RFK is a wire resistance wound on a mica cement coated plate, immersed in quartzite sand and placed in an anodized aluminium casing. Sealing is carried out using silicone elastomer and aluminium cap. The RFK can be purchased on the website in the version with UL marking. RFK models 600 and 800 are particularly suitable for the railway sector and have an IP65 degree of protection.

Overview Table

Min Resistance
Max Resistance
Tolerance (%)
Rated Continuos Power (W)
Protection Degree (IP)
Not Inductive
Rated insulation voltage (V)
(Clarification on Voltage definitions.pdf)
Thermal switch

These options are available for this product:*

ohmic values out of range,special tolerance on resistance (2%, 1%),special cables,different cable lenght,heat-sink mounting,special cables,thermal switch
*Options must be ordered separately. Contact Fairfild directly.

In what sectors is this resistance used?

The main areas of application are industrial automation, energy and railway sector.

For what types of applications is it used?

The product is used: as a dynamic terminating resistor, as a basic element in harmonic filter circuits as a charge and discharge capacitor resistance in RC circuits.

What are the electrical specifications?

The RFK family has 5 models with power ratings from 90 W to 450 W and the ohmic value ranges between 0.43 Ω and 51K Ω. The RFK version marked UL has 3 models with power ratings from 75 W to 150 W and the ohmic value ranges between 1.5 Ω and 3.6K Ω. The maximum operating voltage is 1500 V for models 250-350-500 RFK, 2000 V for models RFK 600-800 and 600 V for RFK UL version.

What are the overload conditions?

The resistance can be overloaded with respect to its nominal power based on the working cycle (insertion and rest time). For duration pulse less than one second, the overload permissible also depends on the ohmic value. For pulses of longer duration, the internal quartzite plays a decisive role in dissipating energy. See the section on overloads in the data sheet.

What is the temperature of the resistance?

The temperature of the resistance depends on the power that it will dissipate. Numerous factors influence the dissipation capacity; please consult our technical data sheet for detailed information. The graph of the data sheet shows the relationship between the temperature on the casing and the power applied for a heating element placed horizontally.
The resistance can be installed horizontally or vertically, in this case it is necessary that the cables are facing downwards. For mounting use the 4 holes available, 2 holes in the case of the 600 and 800 RFK models. The provided cable that has not been stripped is used for electrical connection. There is no hole for the earth connection. The case is provided anodized. The flat shape of this resistance makes it particularly easy to fit into electrical panels.


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