Metal Halide Lamp on Uninterrupted Power Supply

I'm certain that some UPS can easily drive a Metal Halide lamp. I'm equally certain that some UPS cannot drive any of these types of lamps.

I flipped a coin and it tells me that you cannot do this with your supply and lamp.

It depends rather a lot upon the rating of the UPS and the rating of the lamp, neither of which have been shared with the forum.

You guys and your negative waves.

Sure you can drive a MH lamp with a UPS.

Next question?

I guess I should have used another coin.

Another p** grower trying to save his crop after a power loss eh?

With enough money, you could connect whatever you like behind a UPS. But as the size goes up and/or the type of load gets more demanding, the cost of the UPS goes up exponentially. I once did a system for military temporary radar stations where they wanted to be able to hold up a small air conditioner for the building for 3 hours in order for them to have time to get fuel for the backup generator if necessary. It took a 25kVA UPS system to run a 2HP AC unit for that long and ensure that the starting surge for the motor would not shut it down towards the end of the battery life. So it cost them about $30K at that time to be able to accomplish this.

I hope you get a good price for that crop...

Tsk, Tsk, a suspicious and inventive mind.

Metal halide light is a gas discharge tube at its most basic. It has strange nonlinear I vs. V (current vs. voltage) characteristic, Including negative resistance portion of it. Using it straight as a load is an excellent way to kill the power source (that was built for resistive and inductive loads), and at the same time to blow the light bulb too. It takes some solid engineering to match such a misbehaving load to a conventional source.

On a second thought Raef might be right.

Metal Halide lamp has peculiar characteristics. Its body temperature is nearly 40 Deg C or more while in operation. When there is a short power fail of the order of even 0.1 sec, the lamp turns off and unless body temp is down to nearly 150 Deg C or lower it does not light up again- though you have UPS back restoring power even in milisec after say 0.1 sec of power fail. Lamp cooling is dependent on ambient conditions, luminaire design etc etc. It may take 10 to 15 minutes or longer depending on indoor, out door, season etc etc. This is the answer to your question.

To light up a MH lamp one generally applies about 2.5 to 3 KV sharp pulse (pulse width etc- I will not discuss here) - which is generated by teh igniter in combination with normal choke/ ballast.

However I had design, demonstrated and made a metal halide lamp to turn on within about 6 to 8 seconds after a brief power fail like this using specially designed choke and specially designed igniter. So there is a solution too- which is expensive and not commercialized widely - for unknown reasons. I had demonstrated this to reputed lighting companies in India. Hence in case of emergencies, people do install other types of lamps to light up during such 10 to 15 minute breaks.

"When there is a short power fail of the order of even 0.1 sec, the lamp turns off"

If you have a decent Uninterruptable Power Supply that is worthy of its name then that's what you get and uninterrupted power supply that doesn't change when the mains power fails. As far as the load is concerned when the mains power fails nothing has happened and it carries on exactly as it was prior to the mains failure.

Unfortunately there are a lot of cheap and nasty UPSs on the market that either don't supply a proper sinusoidal output or have a change in the output voltage when the mains fails.

So the moral of the story is to stick with a reputable manufacturer that is known to produce reliable UPSs that do what their name states and supply you with uninterrupted power.

You will also need to check with the UPS manufacturer or supplier that the unit you are selecting is capable of handling the start-up power requirements of your specific load which in this case is metal halide lamps.

One thing I would make sure of is that the UPS puts out a true sine wave. Most of the inexpensive UPS's put out a single step modified sine wave. Basically a reduced voltage square wave with a certain amount of dead time between pulses. I don't think that the lamp or, more specifically, it's ballast will work very well on a modified sine wave.

One needs to be practical. I am not sure of end application fro MH being connected on UPS. Let me give you an example of a huge MALL or Parking lot or street light or tunnel lighting. The power requirements are so huge- no break UNINTERRUPTIBLE UPS is not practical and not economical. Hence for tunnel lighting in fact MH lamps are NOT USED at all. In huge malls, diesel generator comes on - but may take a few minutes- during which MH will not light up and will remain off for 10 to 15 minutes, and alternate back up lighting is provided. Another example is day and night cricket matches - which have become now-a days - are played with entirely diesel generator supply to avoid a short break in supply. You can imagine costs involved and even matches can be lost, if there is a short break. You are welcome to look at many sports applications, indoor stadiums and other huge complexes- where such no-break uninterruptible supplies are installed. For one or two 70 w or 150 w lamps it is oK.

CR$ administrators- kindly see spell check is NOT WORKING.

"The power requirements are so huge- no break UNINTERRUPTIBLE UPS is not practical and not economical."

The cost is always a factor that needs to be taken into account but the original poster asked about the use of an UPS and it should be noted that I said:

"If you have a decent Uninterruptable Power Supply that is worthy of its name"

In your situation you are talking of a Backup Power Supply that comes on line sometime after the mains power has failed not an UPS.

However as vargaalex stated in his post one solution is to have small UPS units built into each light fitting that keep the power supplied to the light when the mains fails. That way you don't have to worry about the huge inrush currents and problems associated with starting the light because it will always be started when the mains power is available, all the UPS has to do is supply an appropriate voltage and current to maintain the lights operation. It also means that you don't have to worry about one huge battery bank and a similarly large inverter that supplies the AC power to the lighting system and must be capable of handling the start-up power requirements. You are also not putting all your eggs in one basket so that in the event of an UPS malfunction you only lose one light not all of them.

Most any lights can be powered from a UPS, and those used in some installations for emergency lighting are connected to a UPS.

The real issue is sizing the UPS to handle all the loads connected.

Hallo XYZ, Masu, Varga

I worked in and for telecomm. center most of my life. By necessity, We had always on power supplies. That is the most expensive, most maintenance demanding, absolutely best kind. It is the power thru all the time architecture. Rectifier, battery, DC/AC all the time. Most people and outfits cannot explain the expense, and opt for cheaper alternative. Most of which cuts in asynchronously (with consequences), and usually supports operation, until operation can be shut down in an orderly fashion.

Mostly it is a promise, not fulfilled, with consequences. Fingerpointing follows.

Then history repeats.

Thanks- I like your pointing out ground realities in the field. For telecom exchanges - you need un interruptible supplies. When it comes to a huge shopping mall with say 200 to 300 or sometimes even 500 light points- each fitted with smallest 70w (not 150w) Metal Halide lamps -it is not easy or economical to provide no break power supply.

"When it comes to a huge shopping mall with say 200 to 300 or sometimes even 500 light points- each fitted with smallest 70w (not 150w) Metal Halide lamps -it is not easy or economical to provide no break power supply."

I agree wholeheartedly and this is probably the reason that the original poster has never seen it done. In such situations there are far more economic solutions like self‑contained emergency lighting systems that only come on when the mains power fails.

However, the original poster asked if it was possible to power a metal halide lamp with an UPS which is technically possible given a unit that is of sufficient quality and capacity. Whether or not it's economic or practical is a completely different question.