The main difference is that a VDC (Voltage Dip Compensator) protects against momentary voltage sags whereas DPI (Dip Proof Inverter) protects against voltage interruptions (zero volts) AND momentary sags.
DPI support zone Voltage Sags to Interruptions (zero volts) More DPI info
VDC support zone protects against Voltage Sags More VDC info
Sag: A short-term decrease in voltage lasting anywhere from milliseconds up to a few seconds.
Momentary Interruption:
A very short loss of utility power that lasts up to 2 seconds.
Information:
