Soft Motor Starter.

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Post deleted

I believe these will only work reliably with 3ph motors, 1ph are very tricky to run variable frequency or soft-start.
M.

Why exactly do you need to do a soft start for a 12 volt fan motor? I have never seen any large electric radiator fans on vehicles use anything but direct online through a sufficiently sized relay. The only slight degree of additional current limiting they get is by the wiring itself.

The OP refers to 3ph soft starters, these are often used in place of using Star-Delta starting or where a motor winding-capable is not fitted .
Max.