200amp fuse wire and big inductive voltages

hello
im trying to make anti spsark switch for electric skateboards using mosphets and LTC7000-1
i intend using 100 Amp Tinned Copper Fuse Wire for the fuse want to make a 200 amp switch
is there any reson i cant just use 2 bits of 100a wire for the 200amp switch? or something that may help the fuse ie 2 bits of 100a fuse wire

jonisonvespa:
hello
im trying to make a switch for electric skateboards using mosphets and LTC7000-1
i intend using 100 Amp Tinned Copper Fuse Wire for the fuse want to make a 200 amp switch
is there any reson i cant just use 2 bits of 100a wire for the 200amp switch? or something that may help the fuse ie 2 bits of 100a fuse wire

Never heard of anyone making a switch from two bits of wire. Explain.

Paul

sorry bit confusede, please delete

Not sure your configureation but if you are asking if two pieces of 100A fuse wire connected in parallel will act as a 200a fuse, the answer is NO / maybe.

If you had two "identical" resistors (or fuse wire) connected in parallel, each would get 1/2 the current.

However if the resistors are not exactly the same resistance the lower resistance path will carry a proportionally higher current.

Also keep in mind that fusing characteristics are related to I^2 * t (where I = current and t = time)
So a "fuse" rated to carry 100 amps will likely open at ~ 200 amps after a time. However the MosFets will fail faster than the fuse can protect.

If your goal is to protect the MosFets, look at a circuit that will turn the MosFet off when the current exceeds some safe value.

Fuses are to protect wires from bursting into flames, not protect semiconductors.

To detect high current like this the ASC756 style sensor is a good choice, minimal extra resistance in circuit
and simple to connect to a comparator.

For that sort of high current switching you'll need an array of very low on-resistance MOSFETs in parallel
preferably driven from a MOSFET driver chip to get fast switching (slow switching may allow one device to
hog the current for long enough to overheat).

For instance with 3 5-milliohm devices in parallel each will dissipate 5W at a 100A total current.

100A sounds like a lot - are you sure this is the correct value?

With inductive load you'll need a free-wheel diode of course.

To quote MarkT

Fuses are to protect wires from bursting into flames, not protect semiconductors.

In the early days of transistors, they were jockingly known as "The fastest fuse on 3 legs".

They still are fast to fail, but often they fail shorted, then if enough current is available vaporize/shatter. Failing shorted cascades the failure to other semiconductors on the board typically, and eventually the real fuse!

Hi,
Interesting YouTube testing fake and original 200A HV fuses.

Tom... :slight_smile: