I have an issue I want to know if anyone else has dealt with. I have a large exhaust fan that is driven by (2) 150 hp, 1750 rpm motors. The exhaust fan has a common pulley that is belt driven equally by each motor. The motors are both controlled via the same soft starter and each protected by their own overload. The issue is one motor pulls about 30% higher amperage. Tried a new motor and it too pulls more load. Any ideas?
i'd call it different belt tensions.
one motor is pulling both it's part of the shared load,
and dragging the other motor along with it, as it's trying
to turn the shared load a bit faster than the other motor.
assuming synchronous motors, this is reducing the slip
the slacking motor needs to develop to do the work.
it wouldn't take very much of a difference in tension
to make a fair bit of difference in running loads.
i'd get two new belts, from someone like gates, not
cheap import stuff, and tension them the same.
you'll need a decent tension gauge... here is one:
http://www.gates.com/products/autom...fessional-tools/krikit-v-belt-tensioner-gauge
i'm not sure if that one will handle the belt size you have.
there are others available, but that one is reasonable.... about $30
with two separate v belts driving a common shaft, it's going to be hard to have them both
perfectly sharing the load. as the belts wear, things will change. gilmer belts would solve
the problem, but cost a lot more. i'm assuming the equipment doesn't have spring loaded
belt tensioners. if it has tensioners, i'd set the belts up without tensioners, with a gauge,
then drop the tensioners into place, run the belts a half hour, stop and measure the tension
of both belts at that point.