Traumflug: I've had fuses blow in much less than a second when drawing more current than they're expected to carry, especially if they're fast-blow types.
Sure, PTC fuses may take this (but then again, I'd not run them at 24V since some of the ones people put on boards aren't rated for use above 16V), and slow-blow fuses should be fine too, but whether a fast-blow fuse will go depends entirely on the PWM and the amount of current drawn and to some extent just how fast a fast blow fuse it is.
Specifically, if you're already close to the current limit of a fuse and then try doubling it while using PWM to "limit" the max current, I would expect the fuse to blow pretty much every time. If you were no where near the limit, then you might be fine, but I know I'd prefer not to take a risk.
Sure, PTC fuses may take this (but then again, I'd not run them at 24V since some of the ones people put on boards aren't rated for use above 16V), and slow-blow fuses should be fine too, but whether a fast-blow fuse will go depends entirely on the PWM and the amount of current drawn and to some extent just how fast a fast blow fuse it is.
Specifically, if you're already close to the current limit of a fuse and then try doubling it while using PWM to "limit" the max current, I would expect the fuse to blow pretty much every time. If you were no where near the limit, then you might be fine, but I know I'd prefer not to take a risk.