It is the motor thermal breaker. Not the 20A branch.
It trips after several boards, about in the middle or later. So conclusion is duty cycle thermal overload.
It is well documented this is no 15A appliance, even with steel head. How UL and CSA allow a 15A plug I do not know.
I need to do one further test as the cheap thermal breakers in these things fatigue. It could be tripping at a bit low. I need to glue up some scrap oak into 10 wide to test max loading.
Summary of 15 inch 3 HP fixed bed planers. Number of bits is a little misleading as their size differs. Looks like only two basic sets of castings. Small differences in how they are executed. With the castings about the same, weight differences may be more in the base. They only need to be as smooth as a quick pass with 220 and 320 paper. Laguna only has a 5 HP and Delta only strait cutters. Harvey does not make one, It seems most companies are expecting availability in early September. So for now, just patience. Run a board or two, take a break.
Jet seems to be the newest design. If the fit and finish of the PM is still tops, then it is probably worth it. Unfortunately, at least in drill presses, it is not what it was. Oliver may be a best buy. Again, what we don't know is the quality of motors, bushings and bearings. There are no actual objective tests or even decent internal evaluations.
ShopFox W1874 $2274
48 bits 3/16, 6" min 48", 302 lbs
Lower motor, ribbed belt
Grizzly G1021X2 $2600
52 bits, 3/16, 6" min 48 bed
Lower motor, triple V belt
Oliver 10014 $2600
52 bits, 3/16, 6" min, 48" 401 Lbs
Lower motor, Built in Wixey DRO,
Jet JWP-15BHH $2750
48 bits, 3/16, 5 3/8 min49", 285 lbs
Lower motor, ribbed belt, Air strut cutter suspension ( just a piston to make cranking easier I think)
Rikon 23150-H $3324 ( with shipping)
72 bits ? x ? min 44" 492 Lbs
Top motor, triple V belt
Baileigh IP156-HH $3358
68 bits, 3/16, 6"min 48 bed, 448lbs
Lower motor, triple V belt,
Powermatic 15-HH $3500
78 bits, 3/16, 8" min, 48 bed, 502 Lbs
Lower motor, Built in casters, triple V belt
South Bend SB1108 $3545 ( wow, $900 to add a $60 DRO to a Grizzly!)
52 bits, 3/16, 6" min 509 Lbs
Lower motor, Triple v belt, DRO