After I have been learning that some Japanese mercury vapor reactor ballasts consist of an oversized power factor correction capacitor potted within the ballast’s casing in order to have a lower startup current than typical high power factor reactor ballasts with a normally sized power factor correction capacitor potted inside the casing, I am beginning to wonder if there is a practice involving the installation of oversized power factor correction capacitors in European HID fixtures using reactor ballasts in order to keep startup current minimized.

Some of the reasons that I have read in some Japanese HID ballast documentation say that having an oversized power factor correction capacitor wired in parallel with the mains is good for installations where the startup current of ballasts with normally sized power factor correction capacitors affects the operation of other electrical appliances and good for installations where the wiring size is limited.

Here is a translated excerpt that I got from a Japanese HID ballast document regarding applications of oversized power factor correction capacitors in HID reactor ballasts:

“ Low starting current ballast:

The power factor improvement capacitor of the choke coil type ballast is enlarged, and the capacitor leading current is increased. This reduces the input current at start-up and reduces wiring capacity.

This is suitable when the power supply voltage fluctuates little (within ±6%) and the power supply wiring capacity is fixed.

This is suitable when there are problems with the operation of other equipment when starting a lamp.”

Here is the documentation where I found this information:

https://www.seiwa.co.jp/support/pdf/101N-8_%E3%83%A9%E3%83%B3%E3%83%97%E5%AE%89%E5%AE%9A%E5%99%A8.pdf

The information can be found on page 366 of the above document.

I think in Europe you are not allowed to oversize the power factor correction.
One of the problem is a safety hazard: If capacitive net load is present on a network and there are some induction motors running a lot of inertia, a power cut upstream will make the motors turn into generators, the capacitive net load will keep them excited and create very large overvoltage till the motors spool down.
That is the reason the PFC's are slightly lower than required, if there is a need for some tolerance. Undercompensating makes the motor lose excitation, so the voltage collapses quickly, so no overvoltage.

Cold HID lamps have low arc voltage (can get as low as 20V for the first few seconds in an 100V-arc HPS). At this time the ballast pulls higher than normal current, at very low inductive power factor. A higher value capacitor will reduce the current draw in this stage

But there are some reasons why NOT to overcorrect the power factor this way :

1.
The purpose of power factor correction is to prevent reactive current going in the supply lines, causing unnecessary losses and loading of the power line

The problem is not only for the lighting circuit itself, but for the main feeding cables for electrical installations that power also other loads - which are already "undersized" due to diversity factor of those other loads. (The diversity factor of lighting is 1, but of entire installations can be anything like 0.5..0.7)

So it makes the most sense to optimize the capacitor value to correct the power factor as precisely as possible in the long run when the lamps are warmed up, not in the short period when they are cold

2.
The circuit conductors and circuit breakers can take some overloading for short periods, which is adequate for letting HID lamps warm up (even if it starts at 2x current, as long as it goes down fast in the first few seconds after that, and stabilizes at 1x within a few minutes)

3.
The capacitors have extremely high inrush current at the moment of connecting to the line (the first AC half cycle), which is proportional to the capacitance and circuit impedances

Higher capacitance makes the circuit require bigger switching gear (switches, contactors) to withstand this inrush, and may get close to the limits of magnetic tripping (short circuit tripping) of circuit breakers immediately at switch on, especially if "B" breakers are used (as is common in some places in Europe)



The capacitors in European gear are normally sized to correct the power factor to about 0.9L to 0.95L (L=inductive) for the condition with warmed up lamps at full power, and rounded to the nearest standard capacitor value

This in theory leaves some more capacity to go before getting to PF 1.00 or even more before 0.9C (which may be still acceptable), but probably not that much, and i wonder where the oversized capacitors actually are on this scale

Medved :

But this problem will also exist if the power is interrupted 2 times, the first time extinguishing all HID lamps, the 2nd time stopping the motors with "unloaded" capacitors of the entire lighting installation...

I just find it strange that Japan sometimes likes to do things differently than most other countries. That is why I honestly love importing lamps and lighting equipment from Japan.