Size and weight of the cables to connect it... Often not thought about until it shows up on site. Biggest one I have done was 1,250HP @ 480V, the cables were slated to drop through the floor and run about 350' on a tray suspended from the ceiling of the room below. But the weight of all of those cables exceeded the limit of the tray (which was already run before we got there). Major kerfuffle that held up the job...
On the big PowerFlex VFDs, you have to decide on ordering it where you want the cables to exit, changing that in the field is a major undertaking. Standard is bottom exit, but to make it top exit you have to add another cabinet and bus extensions. I've done it in the field, it's possible but not fun.
Hopefully they ordered the little hydraulic cart that you use to remove the power modules, because the connections are BEHIND them. Without that cart, the power modules can still be removed, but it's a definite 2 man operation and they are super top heavy, so you have to be extremely careful not to drop them or let them fall over. The cart grabs the sides and holds them, then wheels them out really easily. If they did not order the cart to go with it, they are around $2k I think, but may take a week to get on-site.
