There is a wide range of AC motors since they can be used in numerous applications. AC motors need to be protected but protection selection usually does not depend on the motor and load type. This selection is based on the fundamental AC motor operation processes. There are crucial differences between the protection of induction motors and synchronous motors. Motor operation characteristics have to be particularly considered when applying selected protection. This approach is more important for the motors than for any other power system element. For example, the starting and stalling currents/times have to be known and taken into account when using overload protection. Also the thermal withstand of the AC motor has to be precisely defined under balanced and unbalanced loading conditions. The conditions for which AC motor protection is needed can be separated into two main groups: imposed external conditions and internal short circuits. This course is suitable for electrical engineers with a desire to understand the fundamentals of AC motor protection. Presented details cover issues related to protection against external and internal motor faults. Upon successful completion engineers will be able to address AC motor protection terminology and concepts and techniques that are used for overload, single phasing, under-voltages, unbalanced supply and reverse phase sequence faults. Learning Objectives This continuing education course is intended to provide you with the following specific knowledge and skills:

• Thermal (overload) protection
• Start/stall protection
• Short circuit AC motor protection
• Earth fault protection
• Negative phase sequence protection
• Protection against faults in rotor windings
• Under-voltage protection
• Under-frequency protection