Make sure your processes are running at peak performance before hitting the reset button again.
Motor overloads occur when the motor draws too much current. The main problem with excess current is that it creates heat which degrades the insulation surrounding the conductors that create the stator magnetic field. Continued degradation of the winding insulation leads to insulation failure and eventual motor failure.
It is important to recognize that an overload condition exists, but it is equally important to determine and correct the cause of the overload before attempting to restart the tripped motor.
There are many reasons why motors draw excess current, but they can be categorized as mechanical, electrical, or load related.
Mechanical problems include (but are not limited to) mass imbalance, shaft or bearing misalignment, belts that are too tight or loose. These faults are the most common sources of vibration associated with rotating equipment. Approximately 30% of the time, when these sources are present, they will create a resonance condition. Resonance occurs when the frequency of an oscillating force approaches the natural frequency of a spring system. Resonance is a huge energy thief and will create an increased load on the motor.
Electrical problems can be a cause of incoming power, such as voltage mismatch, (over or under voltage), voltage imbalance, or excessive harmonic content. Degradation or breakdown of winding insulation can cause intermittent faults. Since electrical insulation has a negative temperature coefficient, these faults disappear after the motor is stopped and the insulation cools. Electrical problems with the rotor, such as static or dynamic eccentricity, cracked or broken rotor bars, or casting voids, will cause the rotor to operate below rated speed, which reduces the counterphase created by the rotors spinning action and will cause the rotor current to increase.
Process or load problems, such as excess flux, cavitation, or flux resonance, will also cause the rotor to operate below rated speed, which will cause the motor rotor current to increase, creating an overload condition.
To protect against these faults, motor controllers have protective relays (overloads) that automatically remove power from the motor to prevent these faults from causing catastrophic motor failure. In most applications, motor tripping is the first indication of a problem in the motor system.
When this occurs, operators may attempt to restart the motor 3 times before contacting maintenance. However, depending on the cause of the overload, these restarts may exacerbate the problem and lead to further motor damage or catastrophic failure. Restarting the motor does not fix the cause of the excess current.
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Provides an easy-to-use handheld instrument that can give you a complete and thorough examination of the engine system from the Engine Control Center (ECC) in less than 3 minutes. These tests ensure that the engine is “safe” to restart. This instrument will quickly assess the condition of the ground wall insulation, winding insulation, and any developing rotor problems, and will evaluate the condition of the engine and display its status on the instrument screen in one of three conditions: “Good,” “Warning,” or “Bad.”
After the engine is restarted or even before the engine is tripped, the engine will be tested in a timely manner.
It can be used to assess the entire motor system, from input power to the entire process itself. ATPOL III™ uses motor voltage and current to fully analyze the entire motor system while the motor is running under load. ATPOL III™ performs simultaneous data capture of all three phases of voltage and current to quickly assess any power issues that may be causing the motors to increase current. It also performs A/D conversion of the motor voltage and current which is uploaded to the ESA software to assess the electrical and mechanical health of the motor, as well as the mechanical health of the driven machine.
After resetting the overloads, the operator will restart the motor. If the motor runs successfully, this is usually the end of the situation. However, the reason why the motor tripped is still unknown and could lead to more trips in the future. Typically, each subsequent trip occurs at reduced intervals, indicating further degradation of the motors health. However, before restarting the engine, some basic mechanical and electrical checks should be performed.