I have some experience with LTspice but am by no means an expert. I'm trying to simulate 1- and 3-phase rectifiers (see attached) and the simulation time is at a near standstill. I understand that this is common when errors or exist or in simulations involving high frequencies. However I don't believe either are the case here. This seems very straight-forward... what am I missing?
The inductor you added at the input is causing high frequency oscillations, which require a lot of processing time to calculate. If you magnify the thick part of the trace you will see them. Remove the inductor and the simulation will be very fast.
The 1N4148 diode has a 0.2A maximum rating. You are applying a 5A load which will zap the diodes.