Wirewound power resistors are usually rated with respect to continuous power, which can be insufficient for e-mobility applications. A typical application is the pre- and discharge of large capacitors, often referred to as “soft start.” In this case the pulse-handling capability of the resistor is also very important. This capability can be determined over a large range of pulse durations by combining theoretical basics with finite element simulations of the respective thermal performance. The results can be generalized so that changing customer specifications can quickly be evaluated and suitable resistors suggested. Microhm Electronics provides wide range of wirewound resistors, such as AHW, GTW,MTW, NTW, VEW series and more.

 
Wirewound power resistors are typically specified according to their continuous power rating. However, the resistive element, the wire, can pick up a relatively large amount of energy while undergoing only a moderate temperature rise due to its relatively high mass and heat capacity. This is why wirewound power resistors are the perfect choice for pulse load applications.

 
Should the resistor be stressed by a pulse for a duration that is not in the range of those given in the datasheet, and which is not in the range of adiabatic boundary conditions, then it is difficult to calculate the maximum permissible pulse load. However, a combination of theoretical basics and finite element simulations allows for calculating the thermal performance of a resistor over a virtually unlimited pulse duration interval, i.e. from very short pulses to continuous power.


Limiting the charge and discharge current of capacitors is a typical application for wirewound power resistors in the e-mobility sector because of the respective high pulse load. Soldering all electrical components to a PCB may be preferred instead of using “external” resistors, in order to keep the production process as simple as possible. In this case a number of smaller wirewound power resistors are directly soldered to the PCB, replacing a single large wirewound power resistor.