Motor Protection Practice Exam

Phase sequence protection is a critical safety measure in three-phase electrical systems. Its primary function is to ensure that the correct phase order is maintained in the electrical supply. When motors or other three-phase equipment are connected to the power supply, they are designed to operate optimally with a specific phase sequence—typically designated as R, S, and T. If the phase sequence is incorrect, it can lead to several serious issues, such as reversed motor rotation, which can cause mechanical damage, affect operational efficiency, and even lead to catastrophic failures.

Maintaining the correct phase order is particularly important in industries where the orientation of machinery is critical, such as in conveyor systems, pumps, or mixers. If a motor were to run in the wrong direction, it could result in damage to the equipment, production downtime, or safety hazards for operators. Therefore, phase sequence protection devices monitor the sequence of the phases and will trigger protective measures, such as disconnecting the motor or alerting operators, if an incorrect sequence is detected.

In contrast to this, other options such as low voltage protection or electrical consumption monitoring do not address the specific requirement of ensuring that the phase sequence is correct. Furthermore, phase sequence is only applicable to three-phase motors, making it indeed relevant specifically