My experience has been that the weakest link in that area is a crappy
socket. A lot of the cheaper ones use only the edge of the flat metal for
contact on the plug (male) blade. Causes a lot of overheating, which makes
the already poor contact even worse. A good socket will contact the entire
width of the blade. Hubbell twist-locks are the way to go for higher
current use, but at $20 - $30 each, not too attractive. As with Gunner's
comment, 50A range plugs have served me quite well, even at full rated
current.

Joe

Bob AZ wrote:

From years of experience let me say this. Most plugs are worthless at
continuous rated service and right along with this most plugs are junk.
There are some good ones but to be safe never count on more than 50%
using rating. Especially for continuous service. The best of them fit
well and this is apparent when you use them. Along with all this you
need good receptacles and preferably the same barnd. Hubbell and
better. Twice the money almost everytime. For 50 Amps I would uese 100
Amp rated plugs and if not the largest rating you can afford and have
space for. Especially for motors and other inductive loads.

Bob AZ