Scott Kreitzer

Motor field protection and recommended settings and monitoring

Proper alarm and trip settings of induction motors may not be as obvious or as straightforward as one would believe.. Motor manufacturers can provide recommended control settings, but these settings may not be truly right for generic applications and typical conditions. There are many reasons why a particular operating condition (whether load related or environmental) may be different than the generic one. In certain situations, typical recommended settings might be too high to warn the user of a potential problem, while in others, the settings may be too low, causing nuisance trips. Trending will provide much more insight than relying solely on setting absolute values. It is important to understand any changes that go on within the motor, which could point to a potential on-coming problem. If an alarming trend is identified that cannot be associated with a change in operating conditions, then the motor condition can be better understood.

NEMA Application Guide for AC adjustable speed drive systems

The application of AC adjustable speed drive systems has presented many unique challenges not only to electrical equipment manufacturers, but also to electrical equipment end users as well. In an effort to aid the user in proper selection and application of AC adjustable speed drive systems, the National Electrical Manufacturers Association (NEMA), through combined efforts of its Motor and Generator Section and its Industrial Control Products and Systems Section, has recently published an Application Guide for AC adjustable speed drive systems. This paper summarizes key topics addressed by the guide that will enable the user to avoid common application pitfalls and assist the user in clearly communicating critical application information and requirements to the electrical equipment manufacturer.

Induction Motor Vibrations

Good motor performance depends on the electrical and mechanical design, as well as on motor operating conditions. Sound mechanical design reduces the vibration levels and extends the life of the machine. Over the years, the demand continues to grow for motors with greater reliability. When done properly, a high degree of reliability can be achieved while keeping economics in mind. This article discusses induction motor vibration, how the American Petroleum Institute (API) 541 views it, and what it means to the customer and manufacturer. It also discusses the evolution of the standards commonly used today and how the various requirements attack different vibration concerns. Any reference to API vibration in this article refers to API 541 fourth edition, unless otherwise stated.

The Effects of Structural and Localized Resonances on Induction Motor Performance

Troubleshooting resonance problems within AC induction motor systems has always presented difficult challenges for motor manufacturers and end users alike. Often the changes in structural stiffness from a motor manufacturers rigid foundation to a less stiff field base can produce drastically different vibration performance. In most cases a structural natural frequency of a motor or foundation that coincides with a motor forcing function will provide detrimental results to the motor vibration. Many times the effects of undesirable system resonances may be detected after the motor has been installed, causing costly down time or even motor failure if the problem remains undetected. Additionally, natural frequencies of motor components, such as fans, may cause catastrophic fatigue failure when the motor is subjected to forcing functions with frequencies in the vicinity of these localized resonances. This paper will provide insight on motor system resonances and localized resonances that may be damaging to an induction motors operation

Selecting ASD systems

This article covered a large number of issues that are addressed by the NEMA Application Guide for Adjustable Speed Drive Systems that must be considered for successful application of an ASD system. The material covered here should be helpful in bringing issues to light that may be critical for the application engineer to consider while creating an initial specification. It is clear that such a specification must consider the interrelationships between the driven load, the motor, the control, and the utility power supply. The authors believe that all users of ASD systems would be llserved by having a complete copy of the NEMAs freely available application guide for ready reference when planning and installing a new ASD installation.

Induction motor vibrations in view of the API 541-4th edition

This paper discusses induction motor vibration, how API 541 views it, and what it means to the customer and manufacturer.Good motor performance depends on the electrical and mechanical design and the motor operating conditions. Sound mechanical design reduces the vibration levels and extends the life of the machine. To follow and understand the API 541 specification, this paper will discuss the following topics in detail: 1.) Overall motor construction as it relates to vibration 2.) Rotor construction: benefits and drawbacks 3.) Bearing Types: benefits, drawbacks and performance 4.) Motor vibration: what it means, magnitude, phase angle, and frequencies 5.) Factors affecting motor vibration