I wonder if anyone can provide the definitions for all ballast types that are used to operate HID lamps such as lead-lag, simple reactance, CWA, CWI, HX HPF, HX NPF, etc. In addition, can someone give a detailed explanation of why some HPS mercury vapor retrofit lamps are NOT compatible with constant wattage ballasts?

Look throughout the gallery and try to spot the different ballast types. I'll throw a few hints :

Choke (reactor) is used where the line voltage is high enough to be suitable as Voc for the lamp. This is the case in Europe for most lamps and in the US for 55V HPS

HX are transformer and ballast combined in one unit, using a core with magnetic leakage path. They had been used in some very old LPS luminaires and are also common in the US

CWA is a constant current output autotransformer, using magnetic shunts and saturation effects to get current control

CWI is the version of CWA with completely isolated primary winding. It's isolated from the secondary lamp circuit, allowing the lamp circuit to be electrically floating or Earthed at an arbitrary point. It is common in Canada for ballasts with Phase to Phase input voltages



I think what happens in the HPS vs CWA case is the lamp can get into a positive feedback condition, that can drive the lamp into an overload : The lamp arc voltage rises as the lamp heats up. The rising voltage on a CWA ballast causes rising of power supplied to the lamp, so further heating, and so on (The Constant Wattage behavior of CWA assumes constant arc voltage, which is correct for Mercury and many MH lamps, but not HPS). This will likely lead to lamp cycling and very short life

For some reason, I see that many US HPS ballasts from 150w S56 to 1000w S52 are CWA ballasts. Plus, I wonder how US high wattage HPS lamps are able to have a long life on CWA ballasts?