The effects of load types on the behavior of AC motor drives during voltage sags

Voltage sags are a frequent cause of disrupted operations for many industrial processes. This paper analyzes the effects of different load types on the behavior of AC motor drives during voltage sags. Voltage sags cause a voltage drop on the DC-bus of a drive, which may cause the drive to misoperate or trip offline. The tripping or failure of a drive due to a voltage sag affects the output torque of a drive-fed induction motor and, thus causes the connected load to operate abnormally. The impact of voltage sags on a load depends on the behavior of the drive, the type of load, the motor´s inertia, etc. This paper discusses mathematical models for a drive, induction motor and various loads. It explores torque and speed variations of constant, linear and quadratic loads during a voltage sag and the subsequent voltage drop on DC-bus of the drive.