------Question for 166.7000.5102 Please Put your question below------
Hi
This product is listed as a time delay fuse but in the product attributes is says it is a fast blow which contradicts it’s purpose. Please can you clarify what kind of fuse it is? Will it blow as soon as it is subjected to over 10 amps or is it able to sustain an over current spike? Example - car radiator cooling fan switching on and spooling up to speed.
Greetings,
All melting-element fuses of the type have some degree of tolerance for current surges, it is simply a matter of degree. Rather than relying on vague descriptions such as “fast” or “slow” it is advisable to consider the I2t rating which is described in this post and other resources.
Welcome to DigiKey’s TechForum,
The datasheet notes the Minimum and maximum opening time in relation to the % of the current rating.
Datasheet
If your close to the rating like 110% listed here it can take a long time for the fuse to blow. If your initial spike is 200% of the current rating it can blow quite quickly as noted above.
Helpful post regarding Fuse I2T rating. Fuse I2T Rating, Melting Point, and Interrupt Rating
Thank you very much for the responses. I have to admit that I didn’t understand all of it. I’m an aircraft engineer of mechanical bias. I have asked the cooling fan manufacture the current draw when the fan spools up as it is probable that it will draw over 10 amps but, I don’t know how much it will pull or for how long. I don’t think it will be a square form pulse. I would appreciate your help to try and sort this out.
Got a degree in mechanical myself before turning to the dark side… Not sure how much thermodynamics or material fatigue were part of your background, but idea from those fields are basically what’s driving here.
There’s a certain amount of energy required to heat up a fuse element to the point that it melts and opens, given a cold start and a fast enough event that heat lost to the environment is negligible. This is basically what the I2t value of a fuse is describing.
During continuous operation, there’s a balancing point at which heat lost to the environment is just barely enough that the fuse element can hang together. Loosely speaking, this is what a fuse’s nominal current rating describes.
As for fatigue, the closer one takes things to the point of failure on a typical event, the lower the number of events that are needed to see failures from material fatigue. That’s what pulse withstand charts like the one below are communicating.
There’s really no good substitute for characterizing the load’s transient behaviors and checking the numbers if one wants to be thorough about things, though I suspect the number of instances where people just apply some padding to the load’s nominal current figures and hope the startup part works itself out is not that small.
I was more aerodynamics and structural fatigue, but that was a long, long time ago!
I think this thread is getting a bit deep for what I need to know.
Long story short wanting to fit modern fans to new alloy cooling rad. Car is 34 years old still running original cooling motors. There are 3 fans (11.5inch diameter) with a 10 amp fuse for each fan. I am not changing any of the existing cooling electrical system apart from the fans (and possibly slow blow fuses).
Three 10 inch fans are what I am looking at for replacements. Modern fans (Spal) have typical running current rating of 6-7 amps depending upon model.
Question is will the time delay fuses be adequate for use with modern fans as it is only a few milliseconds that the motor inrush current event happens?
I have heard of other people who have done the same mod as I am planning just putting 15 amp fuses in to replace the 10 amp. This did make me raise my eyebrows, and is not an avenue I am going down.
In a simple fan system the purpose of a fuse often is only to prevent the wires’ insulation from melting when the fan motor fails with a dead short. There is usually a huge difference between those two currents.
For the 11.5"(292mm) fan I found the A1G280-AA79-11-ND.
A1G280-AA79-11 ebm-papst Inc. | Fans, Blowers, Thermal Management | DigiKey
As for the fuses. What are the dimensions or size callout that you are needing?
The below link shows what we have for automotive fuses 10-15A.
Automotive Fuses | Electronic Components Distributor DigiKey
