MYPV ClearSky Plus, User Manual

Page: 24 / 106

Theory of Operation 24
Most likely you’v experienced a smaller example of these phenomenon in a building that
has large HVAC units. When the compressors first start, the sudden additional load will
cause lights to dim or fluorescent lights to flicker briefly. Both observations are the result
of these power quality issues.
In a commercial application such as HVAC, compressors may be fitted with a “soft-start”
device that stores energy in anticipation of the start-up, providing additional current
reserves to remove the instant burden from the building’s electrical system.
Due to its size, there is no economical “Soft Start” option for a solar Facility, until now.
How Pre-Energization Works
The myPV ClearSky PLUS provides a “soft start” through a process we call “pre-
energization”.
During a traditional energization event, the inrush current is caused because the step-
up transformers need to magnetize, they need to be charged.
Grid Energized, Facility is De-Energized
Electrically speaking, the grid is energized at an interconnection voltage (say 12,470V),
but the step-up transformer is de-energized (at 0V). When the transformers are initially
energized, the amount of energy required to raise the voltage from 0 to 12,470V is the
inrush current.
The myPV ClearSky PLUS “pre-energizes” the Facility’s MV loop and all connected
step-up transformers by directing current flow through a pre-insertion transformer. The