Emam Hashish

An induction motor — Keep it running

This paper discusses factors that affect the life and durability of an induction motor. Various topics include overall construction of an induction machine and its components, field and operating conditions, motor vibration, operating temperatures, installation practice and proper motor selection for special environment and application conditions. Sound motor design, proper selection of the motor to suit the application, proper field installation, and good maintenance are key factors essential for long term motor reliability.

Vibration diagnostic challenges in electric motor applications

Electric motors have unique vibration characteristics mainly due to the coupling between electric and mechanical forces and the construction of their rotors. Rotors are made up of stacked parts and a copper or aluminum cage material that is casted, welded or brazed and shrunk fit on a shaft which may also have welded arms. This built-up construction of different materials with different thermal reactions affects rotor motion in a complicated manner at different speeds and thermal loading conditions. Since motors are the primary source of rotational motion in a typical drive train, high vibration will usually be evaluated on the motor first before moving onto the rest of the drive train components. Unfortunately other components cannot be tested alone to identify if they are the source of the problem. This often results in losing valuable commissioning or operating time. Vibration identifications can be started by using readily available diagnostic tables. Problems can occur when the process of identification goes beyond the capability of the tables to provide a clear answer. This paper discusses case studies on vibration diagnostics of electric motors, where a wider scope of the drive train and its support must be considered in order to arrive at the correct diagnosis. Particular emphasis is given to the identification of the original problem and cause of the vibration issue.

Vibration Diagnostic Challenges: Case Studies in Electric Motor Applications

Electric motors have unique vibration characteristics mainly due to the coupling between electric and mechanical forces and the construction of their rotors. Rotors are made up of stacked parts and a copper or aluminum cage material that is casted, welded, or brazed and shrunk to fit on a shaft, which may also have welded arms. This built-up construction of different materials with different thermal reactions affects the rotor motion in a complicated manner at different speeds and thermal-loading conditions. Since motors are the primary source of rotational motion in a typical drivetrain, one will usually evaluate high vibration on the motor first before moving on to the rest of the drivetrain components. Unfortunately, other components cannot be tested alone to identify if they are the source of the problem. This often results in a loss of valuable commissioning or operating time. Vibration identification can be started by using readily available diagnostic tables, but problems can occur when the process of identification goes beyond the capability of the tables to provide a clear answer. This article discusses case studies on vibration diagnostics of electric motors where a wider scope of the drivetrain and its support must be considered to arrive at the correct diagnosis. Particular emphasis is given to the identification of the original problem and the cause of the vibration issue.

Rotating machines — Pros and cons of monitoring devices

Rotating machines such as motors, generators, turbines, and compressors utilize many different types of monitoring devices. These devices are critical for the long term reliable operation of rotating machines. Some measuring devices will add significant knowledge of the performance and therefore add value and reliability, while others add little to no value but will add substantial cost. The pros and cons of using each of the many different types of devices and what can be determined from the measurement need to be evaluated before installation. Simply installing the device may not add the expected reliability. This paper will discuss parameters of monitoring, setting of control limits, and the application of various monitoring devices.

Longevity of an induction motor

This paper discusses factors that affect the longevity and durability of an induction motor. Various topics include overall construction of an induction machine and its major components, field and operating conditions, motor vibration, operating temperatures, installation practice and proper motor selection for special environment and application conditions. Sound machine design, proper selection of the motor to suit the application, proper field installation, and good maintenance are key factors essential for long term motor reliability and its performance.

Effect of drive system component compatibility on motor vibration

Within the engineering industry, it is a known fact that there are a multitude of cases where the individual components test satisfactorily; however, when the parts are combined, the net sum performance is not as good as the individual parts. Static and dynamic compatibility of the individual drive system component should be matched together in order to achieve a satisfactory system performance. This paper will focus on a few areas where an improvement can be achieved by examining the compatibility of the coupled components. The driver, driven connections, and bearings are the main contributors to the system dynamic compatibility, in addition to the mounting bases and foundations. Motors that are powered by adjustable-speed drives (ASDs) usually require additional design features to accommodate drive influence on the motor. Since these motors run by ASD operate at variable speeds, their dynamic compatibility with the ASD analysis is particularly important.