see the choke as mercury ballast, D goes to ballast, N to neutral and La to lamp.
Usually, CMH lamps are rated for electronic ballast, but they works well with magnetic.
The "Electronic only" is the case just for the 22W version, those need active arctube temperature stabilization and that feature is beyond the reach of the simple magnetic gear.
The 35W and above are officially rated as well for a series choke ballasts, common with HPS lamps (I'm talking about EU-like 230V market only, this does not apply for the US nor CAN, there the HPS spec's are way different).
I have an question for Medved: what kind of ignitors are avaiable?
Usually i use this kind of ignitor, but sometimes i see 4 pin ignitor which take two ballast taps.
The ignitor depicted here is the superimposed type. It contains everything necessary to generate the required high voltage pulse without even needing the ballast inductance for it (so no inductive kick; it would work with any ballast type, include a resistor; but the limit is the lamp here). It's distinctive characteristic is the way how it is connected: "Cut" the wire from the ballast to the lamp and insert the ignitor there.
It is the type usable as well with US ballasts of any type, when remote ballast configuration is required (where the ballast to lamp cable exceeds the ballast specification). In that case the internal ignitor inside of the ballast is deactivated and the superimposed type is placed inside of the fixture close to the lamp. The long cable is then between the ballast and the ignitor. It works just because that ignitor does not need any cooperation from the ballast at all, so the capacitance of the cable to the ballast is no problem at all (with the original ignitor build into the ballast it tend to attenuate the HV pulses).
Other ignitor I have in my hands is the
semiparallel style represented by e.g. SN57. The "ignitor" box is just a 750V (for MH; or 500V for the HPS) pulse generator, feeding tap on the ballast winding in 20% from the line input. The ballast coil then act as the 1:5 step up transformer, so transforms the 750 or 500V to about 3.5 (for MH) or 2.5kV (for just HPS). The main workings (a capacitor in series with a triac) of the ignitor is connected between the tap and Neutral, the connection to the lamp is just a voltage sensing (it senses thge voltage there and based on that determines if the lamp had ignited or not yet, so eventually triggers the triac at the correct moment).
This ignitor system requires the ballast to work together with the pulser box: It forms the switched resonator circuit to boost the 230V to the 750V peak (however it is not sensitive to the actual inductance, it just has to be of sufficient quality), plus uses the turns ratio to transform the pulse to the final 3.5 or 2.5kV.
Because it generates the pulses without any significant losses, it is able to generate rather high energy pulses at every mains half cycle, so it's main use is as high energy, long range ignitor.
Interesting note: If you have a lamp that needs just 750V, you just connect the "tap" and "lamp" terminals of the ignitor box together and connect it behind the ballast parallel to the lamp. It will work exactly the same way as designed, just without the additional boosting, so the ignition voltage would be the 750V (so e.g. to operate US probe start MH on an European series choke MV ballast)
Then in the literature (and if I remember well in one catalog as well) I've seen another form of a semiparallel ignitor: It uses practically the same pulser part as uses to be part of the superimposed ignitors, but it lack the step up pulse transformer, but uses the ballast choke with tap instead. With this type the tap has to be in 6% (for 3.5kV MH ignitor; or 8% for the 2.5kV HPS one) from the lamp end.
Here a capacitor is charged via a resistor (and an filter inductor) till the breakover voltage of a SIDAC (or something similar made of thyristor and few other components), so aboput 200V, then the SIDAC turns ON and discharges the capacitor to the 6% or 8% section of the ballast, so it gets transformed to the required 35. or 2.5kV. As all the circuit is connected around the HV end of the ballast, the inductive filter makes sure the charging resistror does not eat up the HV enmergy.
As the capacitor is charged via a resistor, the pulse energy is rather limited, so these are not suitable for remote ballasts (maximum ballast to lamp is 2m).
Even when the wiring appear exactly the same as with the previous "SN57-like" topology, this is different arrangement, requiring the tap on different position. So you must make sure you have correct ballast/ignitor combination, components of those two styles are not compatible at all (however ballast suitable for both could be made - having two taps, one in the 20% from the line input and second the 6% from the lamp end, then you should make sure you use the correct tap according to what type is your ignitor).
