Ohmwrecker, is it good?
Out of all the games I've played, I've never seen it being used, NEVER. The item only serves for offensive setups, and if you are being offensive and you are tower diving you probably don't need it since you already have a sure lead and the money it costs could be used on a more stat efficient item.
I would actually make it into a more versatile item, using one or two of the next options (not all of them for god's sake): -Maybe making it able to make our own turrets invulnerable for 2.5 seconds too (would help a lot against Rift Herald, since I use that trick with bard and it anulates the first crash hit it does against the turret). -Make it's active boost the next attack of our turret/s to deal increased area damage, minions killed grant gold to the user. -Make it grant more defensive stats and CDR when near turrets, or maybe offensive adaptative stats, doubled when under an enemy turret or the ruins of an enemy turret. -Increase it's base stats.
Consider this item is almost never built, and if it is used you probably want it to be more defensive than offensive, since it is granting defensive stats, it has a good concept but a bad execution, giving it more versatility might be enough to make it shine in the gameplay. Also even through turrets are dangerous early, they do not scale that well into the late game, so having an item only to deactivate them is lame, but having an item for defense is more logical specially in this stale meta where turrets fall apart be it from Zz'rot, Yorick, Rift Herald, or your team being crushed, having more ways to make a comeback should be considered.