undervoltage protection
The effect of a device that, sensing a reduction in current, interrupts the voltage to the main circuits it controls. In an electronic drive, if the input voltage drops below the designed minimum voltage, the drive will protect itself by shutting off the output.

unity power factor
A power factor of 1.0. This is the best possible power factor because all the power supplied is being used. It is achieved when current and voltage are in phase and undistorted.