A motor primer. IV

Much has been written about motors on variable speed drives, high speed rigid shaft motors, impact of the American Petroleum Institutes (API) Standard 541 and motor diagnostics. Most of these papers and articles assume that the reader has significant knowledge of motor theory and operation. However, this assumption is overly optimistic, considering that only a few colleges teach motor theory today and that application experience at motor user locations has been reduced in recent years. This paper is the fourth in a series of papers where the authors provide answers to "frequently asked questions" that are routinely asked by working engineers in industry. The authors present motor theory and application information with an extensive reference list that will help working engineers increase their general understanding and knowledge of motors. This paper focuses on sleeve bearing operation, lateral critical speeds, ambient conditions and motor starting.