...run a 50w MV lamp on a 35w HPS ballast, but limit how much the MV lamp warms up?
A few days ago, I tried to run a 50w MV lamp in a 35w HPS wallpack, with the ignitor disconnected. The lamp started up normally, then warmed up to what appeared to be full brightness, stayed on for 7 minutes, and then went out. While it was on, it looked much nicer than it did with the 35w HPS lamp. I know the reason it extinguished was because the arc voltage got too high for the HPS ballast to provide, but what if there was a way to prevent the lamp from running up to full power? I was thinking of some sort of resistor across one of the terminals to the lamp socket, but I am not sure if this would work. Is there a way to get this to work? The wallpack looked beautiful with the coated MV lamp.

Thanks.

Resistor parallel to the lamp will draw current parallel to the lamp. Higher current in the ballast means higher voltage drop in the ballast, so even less available voltage for the lamp



Besides, consider power dissipation :

The resistor dissipates everything it gets as heat, and if the resistor is of a value tht will "do something", it will dissipate a power around same order as the power of the lamp itself or the ballast losses. Unless you use an incandescent lamp or a high power resistor with big heatsinking, resistor is not an option

The ballast will heat more with the higher current (lamp + resistor). If it is higher than what the HPS draws, it will overheat the ballast. If the resistor is enclosed there too, it will add its own heat in the allready crammed gear box too



To limit the current without affecting voltage as much, limit the current that goes in in the 1st place, dont try to "waste" it. Change the ballast. Add some other choke in series with the 35W one - Try anything between 35W..150W and see what happens

Carefull choice of capacitor may work too, in fact it might work with better results, but do the math first - Adding chokes in series only sums the total impedance. Capacitors cancel out chokes - Choose a wrong capacitor and it will be the same as plugging in the lamp straight to 120V...

The lamp may not like being underpowered - blackening and short life may result



How about using something with actually higher voltage - like 40W Fluorescent ballast (full power one) ?

Lol@ that extinguishing. Lightingguy1994 did that successfully. I guess it depends on the supply voltage. The arc voltage can't exceed 2/3 supplied voltage. Funny you say that, I just found and gimmed a 50w MV ballast on eBay. now I can properly my 50 watt MV, and the setup for the 75w will work too.

Lol@ that extinguishing. Lightingguy1994 did that successfully. I guess it depends on the supply voltage. The arc voltage can't exceed 2/3 supplied voltage. Funny you say that, I just found and gimmed a 50w MV ballast on eBay. now I can properly my 50 watt MV, and the setup for the 75w will work too.

When did you find it on ebay and how much was it? I have been looking for a proper 50w MV ballast long before I joined LG. I kid you not, I check Ebay every day, and have never found one. How did you find it?

Resistor parallel to the lamp will draw current parallel to the lamp. Higher current in the ballast means higher voltage drop in the ballast, so even less available voltage for the lamp



Besides, consider power dissipation :

The resistor dissipates everything it gets as heat, and if the resistor is of a value tht will "do something", it will dissipate a power around same order as the power of the lamp itself or the ballast losses. Unless you use an incandescent lamp or a high power resistor with big heatsinking, resistor is not an option

The ballast will heat more with the higher current (lamp + resistor). If it is higher than what the HPS draws, it will overheat the ballast. If the resistor is enclosed there too, it will add its own heat in the allready crammed gear box too



To limit the current without affecting voltage as much, limit the current that goes in in the 1st place, dont try to "waste" it. Change the ballast. Add some other choke in series with the 35W one - Try anything between 35W..150W and see what happens

Carefull choice of capacitor may work too, in fact it might work with better results, but do the math first - Adding chokes in series only sums the total impedance. Capacitors cancel out chokes - Choose a wrong capacitor and it will be the same as plugging in the lamp straight to 120V...

The lamp may not like being underpowered - blackening and short life may result



How about using something with actually higher voltage - like 40W Fluorescent ballast (full power one) ?

I have tried the fluorescent ballast thing already with an f40t12 preheat ballast. The lamp was not much brighter than an f4t5. It is the only thing that would fit in there. There is a single lamp HPF striplight in the kitchen that will come down soon, so maybe I can check and see how large the ballast is. Would that work if it is small enough?

If a ballast underpowers the lamp (as many ballasts in the US do) the lamp won't get anywhere near 40W in, so it won't warm up, so it stays like F4T5. If the other ballast is full power you got a chance - Try it

Use magnetic ballasts only for HID lamps like that

It costed about $64 so it was not cheap. I also saved "50w ballast" on my eBay searches. I was lucky enough to see it when I was on the bus to the shop class (different building; same school).

When I ran my lamps on the 35w choke, only my symban lamp (larger envelope than normal) would run up and stay lit, but when tried with my normal sized venture 40-50w lamps, it would run up then go out. And both lamps did not strike if they were under 10-15 degrees Celsius

Hey what if there was some way of using both the 35w choke and a F40T12 ballast at the same time? The HPS choke can warm and run up the lamp to full brightness and the OCV from the F40 ballast will keep the lamp lit and start it reliably in cooler conditions

I think the reason my symban 40-50w lamp did not exstinguish was because my supply voltage is usually around 120-125v depending on time of day

If it is so borderline, it will extinguish on the slightest dip - Switching a motor on (air conditioning, well pump, ..)

I gotta say, it did survive my fridge pump kicking on, i remember it flickered when it happened but stayed lit. surprised myself it didnt go out