This paper discusses the fundamentals of motor protection principles. Every motor is designed for a specific operating temperature depending upon its insulation. Once this limit is exceeded its life decreases drastically. Over heating condition may arise due to several factors like supply system disturbance, electrical unbalance conditions, faults, load variation and environment. It is essential to have a proper coordination between development of protection principles and the design of motors to understand the concept of motor heating and how thermal protection for motors can be used to prevent loss of motor life. In this paper an overview of existing protection methods for motors is reviewed with a special consideration of thermal protection of motors.