Hello everyone, trust I meet you all doing good?
As some of you might have known, I’m an Electrical/Electronic engineering student who aspires to become a professional in my field someday. And I’ve begun to explore what the real-world application of what my field really looks like in my own little way. Today I had the opportunity to examine a neighbour’s faulty electric standing fan for its fault and get if fixed if possible. The stated fault of the standing fan as explained by its owner were stiffness of the armature (i.e., the fan blades were experiencing difficulty in rotating), stoppage while it works then picks up again, and afterwards it finally stopped working.
I was also told that when the standing fan Initially began to experience difficulty in rotating, they would pour some engine oil into it through the fan’s rotary control at the top which is attached right behind the motor casing. I immediately told them that was a wrong approach and it could get the electrical motor damaged. So, I then decided to examine the standing fan too see if a could figure out what was cause of the stiffness was, and why it isn’t working anymore.
A clear view of the excess oil present in the fan
I disassembled the fan in no time and I had access to the electrical motor. As I tried bringing out the armature winding out of the filed winding, I experienced some difficulty in pulling the both apart. I noticed that dust had found it way into the electrical motor and couldn’t make it way out anymore due to the presence of the engine oil which seems to be forming some sort of wool-like material when it comes together with the dust, thus making it difficult for the armature winding to freely rotate in the field winding.
Cleaning away dust&oil from the field winding and recoupling it back
I immediately got rid of the dust mixed with engine oil out of the field winding and thoroughly wiped both the armature winding and the filed winding until it had no feel of oil on it anymore. I placed the armature winding back into the field winding and I could observe it was now siting in the field coil freely without any difficulty in rotating. Afterwards, I coupled back the electrical motor and gave it a quick test, but unfortunately it didn’t work despite the armature now being free to rotate.
Cleaning the excess oil present in the fan's stalk
I didn’t fright, I disassembled it once more and went to check the regulatory switch because the engine oil being poured through the fan’s rotary control at the top flows down all through the stalk till it gets to the base of the fan, and the regulatory switch is placed in between the stalk. I opened it up and observed that the regulatory switch had oil all over it. I disconnected the cables connected to it switch and disassembled it and then wiped every bit of oil in it with a tissue paper. Not the best or ideal solution to get rid of oil, but it was helping at that moment. Lol.
Reconnecting the regulatory switch and reassembling the fan's stalk
Oils are generally not a good conductor of electricity and its presence it the regulatory switch could cause it not to work. After wiping it, I assembled it back and reconnected the cables appropriately also. I then gave it another test but it didn’t work still. It was after then I remembered I should test if the coils that made up the field windings if they were still in perfect condition. I opened up the electrical motor once more and carried out a continuity test on the coil and I discovered some parts of the coils didn’t conduct which means it has been damaged. Although the field winding appears physically okay but it has been somehow damaged from within.
Testing for continuity in the field winding
That was when I finally realized what the major fault was. The presence of the dust and oil in the electrical motor contributed to the difficulty in rotation and then probably the coil was experiencing so much heat as it still struggled to excite the armature field to rotate it and then causing a burn to occur within the field winding. Also, the stoppage while working could have been caused by the presence of the oil in the electrical motor or in the regulatory switch. I was able to figure out the all the causes of the fault but couldn’t eliminate them all. So, I coupled the electrical motor back and told them it would be needing a recoil.
Remains of tissue paper used to clean the oil
I couldn’t do the recoiling because I don’t have what it takes to carry out a recoil and I also don’t know how its properly done. I only have a little bit of knowledge on recoiling and how transformers are been made in which I got to learn from @kingtamarah while I was still in my second year in school. So, I had to ask them to send it to an engineer who has attained more level of qualification and knowledge than I.
At the end of it all, I wasn’t disappointed much that I couldn’t get the standing fan completely fixed. I only reminded myself that I needed to up my game and get myself to acquire more knowledge/skills in regards to my field.