Protection principles for electrical motors in the cement industry

This paper discusses the fundamentals of motor protection principle. Every motor is designed for a specific operating temperature depending upon its insulation. Once this limit is exceeded motor life decreases. Overheating conditions may arise due to operating conditions such as power supply system disturbance, internal and external faults, load variation and environment. It is very essential to have a proper interaction between development of protection principles and design of motors to understand the concept of motor heating and how thermal protection for motor can be used in judicious way to prevent loss of motor life. In this paper a brief overview of existing protection philosophy for asynchronous motors is reviewed with a special consideration of thermal protection of motors. Because large synchronous motors are used in cement industry, a review of additional functions required for protection and control of synchronous motors is given in this paper.