A load resistor can be used as a resistive element within systems designed to simulate an electrical load.
In dummy loads, resistive elements are used to simulate the load under which a source would normally operate, dissipating electrical energy as heat.
Fairfild offers several families that can be used as elements for resistive loads, featuring different construction technologies and configurations. Selecting the resistor therefore requires evaluating the characteristics of each model against the requirements of the application.
1. What characteristics should be considered when selecting a load resistor?
Sizing a resistor requires a combined evaluation of several technical parameters.
The information specified by Fairfild includes resistance at ambient temperature and its tolerance, the continuous power to be dissipated, duty cycle, operating voltage, and environmental and installation conditions.
The families in the catalogue also differ in dimensions, continuous rated power dissipation, energy absorption, operating voltage, achievable resistance range and protection degree.
For this reason, when identifying a resistor for a resistive load, the parameters of the individual model and the conditions required by the application must be checked.
2. RXT: load resistors in metal enclosures
Among the Fairfild solutions that can be used as load resistors is the RXT family.
The series uses bare-wire RMS resistive elements installed in an enclosure with a galvanised steel frame and IP23 protection. Versions with IP20, AISI 304 and AISI 316L enclosures are also available.
The RXT 65S datasheet identifies industrial automation and the energy sector as the main fields of use and explicitly lists the product for use as a load resistor, as well as for dynamic braking, neutral grounding and motor starting.
The enclosed configuration therefore represents one of the options available in the Fairfild catalogue for load applications.
3. RMS and RDP: bare-wire solutions for resistive loads
The RMS and RDP families can also be used as elements for resistive loads.
RMS consists of wire wound on ceramic supports mounted on a metal frame. This construction allows the wire to exchange heat with the surrounding air and provides low thermal resistance and high heat capacity. The RMS 10 datasheet also lists use as a basic element for resistive loads among its applications.
The RDP family also uses wire wound on ceramic supports mounted on a metal frame. Fairfild specifies its stainless-steel terminals and construction for high energy loads and heavy overloads. This family is also intended for use as a basic element for resistive loads.
The two families therefore have specific characteristics that should be reviewed in their respective technical datasheets according to the requirements of the application.
4. RCE HP: coated resistors for load applications
For dummy load applications, Fairfild also offers the RCE HP family.
The coating provides mechanical protection for the wire, allows uniform heat distribution and limits thermal expansion of the coils.
For this family, Fairfild specifies a maximum operating voltage of 3000 V and the availability of versions with a mica bar for higher insulation levels.
This technology therefore represents another solution available for use in dummy loads.
5. RCPO and RSPO: larger heat exchange surface
RCPO and RSPO are also among the families indicated by Fairfild for dummy loads. The larger heat exchange surface makes it possible to achieve higher dissipated power values. Both series are also available with an adjustment slider, in which case they are called RCPOR and RSPOR respectively. Power, resistance values and maximum operating voltage vary depending on the model.
6. Different technologies for different load requirements
Load applications can therefore be addressed using different resistive technologies.
RXT solutions use a metal enclosure; RMS and RDP use bare-wire elements on ceramic supports; RCE HP uses coated wound wire; RCPO and RSPO use a configuration that increases the heat exchange surface.
The availability of different construction technologies therefore makes it possible to compare different solutions according to the requirements of the specific application.
7. Fairfild: resistors for resistive loads and dummy loads
Fairfild develops custom dummy loads based on the specific requirements of each customer and also offers several catalogue resistor families designed for this application.
Consulting the technical datasheets makes it possible to review the characteristics of individual models and compare the different technologies available based on the requirements of the specific application.
To learn more about resistors for dummy loads, you can consult the relevant Fairfild application page and the Fairfild catalogue.
For more information and to identify the most suitable solution for your application, contact us.
