powerratingsresistors
I have this wire-wound power resistor that appears to be either ceramic or porcelain in construction with a soft brown plastic or vinyl like coating. I want to find out its power rating. My meter shows about 5.2 ohms. A Google search for 160DR5WL returns nothing.
The voltage rating is for the resistor series typically and specifies the maximum peak voltage you can apply without danger of damaging the resistor due to corona, breakdown, arcing, etc.
The power rating is completely independent of the voltage rating. It specifies the maximum steady state power the package is able to dissipate under given conditions.
You have to conform to both specs. If placing the maximum voltage across the resistor results in more power than the spec allows you have to reduce the voltage until you meet the spec. Likewise you can't increase the voltage above the rating just because you're not hitting the maximum power limit.
Pulse handling is a highly variable characteristic. You can often find this this information in manufacturers' handbooks, occasionally on the datasheet. Some resistors are specially designed for pulse handling capability and that will be well characterized. Things like the trimming method can affect the maximums- I would suggest not taking chances if reliability is important.
Here is such a resistor (Panasonic ERJ-P08J101V surge-resisting) which compares the pulse handling ability with more conventional resistors (note the test limits- 1,000 cycles and +/-5% permissible resistance change).
In this case, a 2/3W resistor can withstand 20-40W for 1msec (depending on type) so your 10x for 1usec seems fairly conservative (at least for the type of resistor I looked at, and with the allowable number of pulses and resistance change).
Best Answer
I cannot say for sure who the manufacturer of this part is. I've used many of these sorts of resistors in my career, so my speculation below is made with a fair degree of confidence.
Renfrew wire-wound resistors that are 8" long and 1 1/8" in diameter are rated at 160W, which correlates with the 160D marking on the part. I'd hazard to guess that it's rated 160W (or very close to that).
R5 on these sorts of parts usually implies 0.5 ohms. The other marks are probably tolerance and packaging codes. If you measure higher, and your meter is OK, the resistor may be somwhat fried.