A Website on Maintenance of Electrical Systems

All motor nameplates are not the same. Each manufacturer would have different items on the nameplate but some of the information on the nameplate are standard as required by NEMA(National Electrical Manufacturers Association) and every motor nameplate would contain this information.  Typically every electric motor nameplate contains The manufacturer name - This information helps to identify who made the motor  Enclosure type  - Written as ENCL informs us of the enclosure type and the cooling method for which the motor was designed. There are many types of motor enclosures, and each is designed for specific applications guided by what location the motor is expected to operate. the most popular one being Totally Enclosed, Fan-Cooled (TEFC) meaning that there is a fan on the motor shaft that cools the motor. Others include (XPRF) for Explosion Proof, (ODP) for open drip proof, (TENV) for Totally Enclosed, Not Ventilated and (TELC) Totally Enclosed Liquid Cooled Vol...

I  resumed my shift, then proceeded to check my email and read the report of the previous shift. They wrote about a breaker tripping continually, stating that necessary checks have been carried out and they figured the circuit breaker was fault. They also advised to reset the breaker anytime it trips until a replacement is made available.  An hour into my work shift it tripped again and I decided to carry out my own checks then I came to the conclusion that the root cause of the tripping was a short circuit.  Due to Insulation degradation, a short happens intermittently and anytime it happens, the breaker trips. When you  flip the breaker on again  it holds but after a while sufficient current jumps through the cracked insulation to form a conducting path between red phase and yellow phase and it trips.  Enough of the back story, I reported to my boss stating that a short circuit was responsible for the continual trippin...

AC contactors are normally not completely noiseless, there is always a degree humming due to  magnetostriction . Magnetostriction  is the   change in dimension of magnetic materials during magnetization . Although when this humming becomes very audible such that it can easily be described as a chatter it raises some questions in the mind of the electrical technician. What causes a contactor to chatter, what is the effect of chattering on the performance of contactor and what can I do to fix it. Common causes of humming in a magnetic contactor. Coil Voltage According to IEC 60947-4-1 the operational limit of the contactor is between 85 and 110% of the rated coil voltage. You should first measure the voltage at your coil terminals A1 and A2 then compare with the rated coil voltage to ensure that incoming voltage to the coil match coil datasheet rating. Undervoltage can cause your contactor to chatter. A 50/60Hz supply voltage would create a...