What type of circuit causes a motor to trip overload heaters during single phasing?

The correct choice is the three-phase circuit, which is pertinent in industrial applications involving three-phase motors commonly used for their efficiency and power. In a three-phase system, each phase is balanced to deliver consistent power to the motor. When one phase becomes disconnected or loses its supply—commonly known as single phasing—this imbalance results in excessive current flowing through the remaining phases. This increased current leads to overheating of the motor, eventually causing it to trip and activate the overload heaters for protection.

On the other hand, single-phase circuits do not experience issues like single phasing in the same way, as they inherently only involve one path of current. Series and parallel circuits primarily refer to the configuration of components and don’t directly relate to the behavior of three-phase motors in this context. Thus, understanding three-phase circuits is essential for diagnosing and preventing overload issues related to single phasing in motor systems.