View Single Post
  #32  
Old 07-15-2016, 01:13 PM
beowulff beowulff is offline
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 14,806
I design lighting control systems, primarily for parks and recreation. Most of the lights we control are HID. We have a feature built into our software that allows "stagger-on" starting, because some parks are billed based on maximum hourly demand, so they want to keep the instantaneous current low. The thinking is that there is a HUGE surge when HID fixtures start, so we offset the time when each pole starts to minimize this. I was always skeptical of this, so I measured a typical fixture, and found that there is an extremely short current spike when power is first applied, but within a few milliseconds the power falls to the lowest level, and then slowly climbs as the lamp warms up.