Very Early Cycling!

[Form109]

just a few days ago i noticed a M250R2 (100 watt HPS) cycling.....and this one isn't even two months old!

whereas the nema that it replaced was burning dimly for years.

[Jace the Gull]

another cause of cycling is the voltage it receives could be too low....

[Medved]

`It look, indeed, as a problem with mains supply - or too low, but more likely fast fluctuating.
Older MV CWA ballasts have quite strong line regulation, so are quite tolerant to these fluctuations, but that concept is not usable with HPS (it would cycle soon too)...

[Jace the Gull]

That's why I believe they made the 3 coil HPS ballast that prevents this problem..is that correct?  But the downside is it makes the fixture VERY heavy and its big..and I'm sure expensive!

[Medved]

Exactly, these are using real magnetic voltage stabilization (on the middle coil, connected together with the resonance capacitor).
The first coil excite the magnetic field in the core, the second is the main stabilization one (it has narrower core portion inside, where the core saturate) and the third one act as energy pickup to the lamp.
Magnetic shunts between all coils cause the coupling to not be as tight:
Between the primary and the stabilization it allow controlled current trough the primary and the shunt between stabilization and the output coil make the output impedance high for the main lamp ballasting.
This setup is not only heavy, but lossy as well - as each coil has it's own dissipation.
The summary would be, then such creation is about three times as big, heavy and have three times higher losses then series reactor ballast for the same lamp (e.g. 150W HPS supplied from 240V)...