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I am creating a 48v system, which needs some precharging to start up nicely.
Now I am using precharge resistors reused from EVs.
I see online available 25W resistors, size them around 90 Ohms, and it will work well.
But what I see from the EVs is for example resistors of 23 or 34 Ohm, rated from 25W to 50W.
However, especially the 23 Ohm one, rated at 50W, at a 400V pack in the Tesla, it would get something like 6000W briefly.
I looked up the datasheet and it says for maximum 5 seconds you can multiply the rating by 5, so 250W.
I know the 6000W will be very very briefly, but still I am a bit confused that they design it like that.
Probably something that I don't get.
The others are Mitsubishi and Volkswagen, both around 33 Ohm, and the Volkswagen one has the same package as online available 25W resistors.
Mitubishi one is labeled at 40W.
Anyway, wether it is 50W or 25W, they all briefly take a beating because current is still pretty high at 300V or 400V right?
Now I am using precharge resistors reused from EVs.
I see online available 25W resistors, size them around 90 Ohms, and it will work well.
But what I see from the EVs is for example resistors of 23 or 34 Ohm, rated from 25W to 50W.
However, especially the 23 Ohm one, rated at 50W, at a 400V pack in the Tesla, it would get something like 6000W briefly.
I looked up the datasheet and it says for maximum 5 seconds you can multiply the rating by 5, so 250W.
I know the 6000W will be very very briefly, but still I am a bit confused that they design it like that.
Probably something that I don't get.
The others are Mitsubishi and Volkswagen, both around 33 Ohm, and the Volkswagen one has the same package as online available 25W resistors.
Mitubishi one is labeled at 40W.
Anyway, wether it is 50W or 25W, they all briefly take a beating because current is still pretty high at 300V or 400V right?