Just tested a 1ph 230v. Amps increase as flow is blocked. 7.2 to 8 amps. Not totally closed off but restricted at outlet by cardboard.
I may have to check that out myself. I know a centrifugal fan will draw less if you restrict the airflow, and does not matter if at the inlet or the outlet, the fact is that the volume of air moved is what puts load on the motor, I kind of always assumed those axial fans were similar in that the volume loads the motor, but I could be wrong.
Ok I'm going to try to respond to all comments. I have tried the blocking the inlet trick. Yes amperage goes down to around 65-67 amps. This is a vain axial fan direct drive, stock fan blade. It has a sister fan on a another bin right beside it. Before POCO changed xfmr I had voltage at 244. When u start this fan, I've saw drops as low as 231-233. I haven't checked the volts since the change out due to weather. I was able to mimic the same voltage drop on the other fan, but not the same amperage conditions. But only once. I'm on the verge of buying a megger or fluke 1505/1520. I'm still not sure using a megger to test is gonna get me anywhere. I guess I could go buy 300' of 40/40/20 URD and quickly be able to determine if I do have a bad UG cable.
Fan specs, GSI group 28" vane axial fan, 1 ph
Baldor UCLE1015
Trust me, I can just about install the Baldor UCL1015 blindfolded, those are all over the place in these parts.
My biggest problem with them is the centrifugal governor likes to hang up and usually in the run position keeping the start capacitor from being put in the circuit at startup. Usually the thing will try to accelerate with just the run capacitor - and this may take out the run capacitor if tried too many times - which could be what you have going on, you said you are losing run capacitors. But most of the time it never gets to full speed before kicking out motor overload device, The fans they put these motors on have such a heavy propeller and because it is a high speed motor and is pushing 12-15 hp out of what is otherwise about a 10 hp winding it takes time to accelerate even with a stout supply and reasonable voltage drop, but I have seen many that run for years in horrible voltage drop situations, the biggest hurdle is starting them, once up to speed the voltage drop usually improves. But at same time that voltage drop is not a whole lot different than using reduced voltage starting as far as the motor is concerned.
The biggest problem I have with using an open air over motor in this application is that it allows enough moisture and dirt to enter the motor and the centrifugal governor hangs up because of rust on the close fitting shaft. I don't know how many times I have been called and fixed that problem, and the next harvest season I may be called back to do it again.
A megger is a handy tool, but generally with these motors if there is a ground fault, the motor doesn't work, and the megger just helps you say it has a ground fault. If you have a high resistance fault, your motor needs replaced or rewound anyway, and the high resistance fault generally wouldn't last for long before you have a fairly obvious ground fault. I have never run into a crop aeration fan motor that was on its way out and causing trouble, they either are toast or need a capacitor or governor switch type of trouble, or have trouble with the control or the supply, anything else electrical within the motor is always replace/rewind time, sometimes they need bearings and nothing else.
Is the current the same at the motor as it is at the overload? If so, the wiring between them is probably not the issue.
If the current is the same at both ends of the wires, my guess is that your load needs more HP than the motor can produce and that is why it is tripping on over current.
A bearing going bad can cause additional friction that requires additional HP to overcome. could be on the motor or the fan itself.
Sometimes you can get mechanical binding of other types as well. I once ran into a situation where a guy had run a screw into the side of something a motor was trying to turn, requiring additional HP.
Sometimes people will take apart a pulley system and put it back together wrong so that it either has the wrong ratio or is binding in some way.
A motor that is misaligned with the load can take additional HP as well.
Like I said I can just about replace that motor blindfolded. There is no pulleys or gearboxes, it is a direct drive fan with the motor located in the airstream so it is also an air over cooled design motor, he said he did send the motor in to a shop, hopefully they would have replaced a bearing if one was bad, and any binding because of misalignment usually means no rotation at all and locked rotor current. Very simple machine, motor with propeller mounted directly on shaft and placed inside a tubular housing that is just slightly larger in diameter than the propeller, usually a 3450 RPM motor.
Both fans are supplied by the same feeder, no? Why is only one of them acting up?
We don't know that they both have the same load (amount of air being moved) even if they are the same identical machines.
