Motor Fault Diagnosis: Overload
The overload fault occurs as a result of loading the motor more than its nominal load value. Initially this results to an increase in current to compensate for the torque and overcome the negative current generated as the result of the overload (Because of flux collision). This compensation stabilizes the function of the motor by using the feedback link between the motor and the generator. The compensation process stops when the generator reaches its current limits.
As a result in minor overload cases the motor will work inefficiently and heat is generated. In induction motors the slip angle in increased. Finally if the generated current is not sufficient to overcome negative current, load, friction the motor enters the locked mode where it is 100% inefficient. In severe cases the role of the motor and load can change, where the motor can act as a generator if the negative current exceeds the generator current.
Overload fault is important to manufacturers because it can result in inefficient production line with less output and a increase in energy consumption. Finally the overload results in heat which can cause insulation melt-down and short circuit and critical failure of the system.
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