Firing up 5k and 10k tungstens without a dimmer

[belford]

Hey guys

Is there any way to start 5k and 10k tungsten units (fresnels) without a dimmer?

Usually these will run over a dimmer board. But you don't have that on location. And carrying a small (haha) 10k dimmer with you also somewhat negates the benetits of not using HMI (tungsten: cheaper, no bulky ballasts required).

Starting the 5k is possible by flipping the breaker a few times in rapid succession until it's not tripping any more, but I consider this an absolute emergeny procedure. It's not good for the lamp and not good for the breakers. And it's just not possible with a 10k (this is pulling more than 43 Amps at 230 Volts when it's running! Not even to speak of the inrush current when starting it cold....)

So, how do you fire those up the easiest, cheapest and most portable way?

belford.

[JD]

Put it on a long cable. (An extra 100 foot #6 cable) The concept is simple, inrush is ten times operating current. A long cable will serve as a resistor and will drop the voltage during the start-up making it easier on the filament and delaying the breaker trip so that you get through the inrush.

[FMEng]

There are circuit breakers and fuses with slower overload response that should easily hold through the inrush of a cold tungsten filament. It's just a matter of using the correct fuse or breaker.

I would probably use a fused disconnect because they will tend to be more affordable. High current time delay fuses are pretty common.

[ariggs]

I know that Mole Richardson makes a 120V 100Amp switch. It's Type 5001762.

It's a lot cheaper than a dedicated 6k or 12k dimmer pack

Picture on the left side

-Riggs

[ship]

Factory stuff is often more economical - can contact other suppliers for distro if too expensive and they I'm sure can pre-figure the inrush currents to the breaker type used also. Mole often not cheap.

High inrush breakers on the other hand a good solution. Didn't do so on a 5K single fixture power supply I recently made and have not had problems with it so far but very likely a delay or high inrush breaker will have been a better choice in breaker.

One concept on the long run however, a switch unless designed specifically as it ain't a circuit breaker. Use a circiut breaker as a switch too much and you tend to burn it up. Better to have both as per design of each.

[belford]

Hi guys

Using long cables is not an option: those need to be lugged around as well and are heavy, just like dimmers. Besides, this will mean that the lamp won't run at 100% output - bad when you need constant color temperature.

I'm not so much concerned about the tripping breaker per se, more about the stress it puts on A) the power grid (the voltage dip from the inrush current can extiguish HMI lights running on the same phase, for example) and B) the lamp itself. AFAIK, especially 10 kWs can fail early and in a spectacular way due to the (mechanical) forces generated by the inrush current. Also this puts a lot of (electrical) stress on all contacts and connectors. I've always wondered whether the switches on the 5k and 10k fresnels are actually just for switching them off or taking them off the dimmer grid for lamp changes? Anyone knows anything definitive here?

Is there something like a dedicated soft-start circuit available that is not a full fledged dimmer?

belford.

[fredthe]

Originally Posted by belford

Is there something like a dedicated soft-start circuit available that is not a full fledged dimmer?

Perhaps just a simple diode, with a manual bypass switch? That would at least cut the power in half.

-Fred

[Chris15]

Inductance.
Lots of it.

Since the voltage a cross an inductor is equal to L di/dt, the current through an inductor must remain continuous. It can't jump suddenly. This is why they are used on the outputs of phase chopping dimmers, to smoothe the curve...

Inductor goes in series with the load. You may need to add a parallel or series capacitance to return the whole thing to having a reasonable power factor.. The value and configuration will require some analysis but it's easily enough achieved...

[mrb]

i think youre looking into it too much. Movie guys run these lights on straight power more often than not. The thing is making sure your supply is sufficient. You dont want to be firing up a 10k light off something tapped into a 100amp panel. And forget about supplying them from any residential power.... get a generator if you need it.

[Edrick]

I was going to say we constantly run 10k lights on set and off location. As far as connecting it to a longer cable (100 AMP Whip) and it effecting color temperature I don't believe I've ever heard of it being an issue and in film we're more concerned about lighting temp but we regularly plug it into 25 / 50 foot whips. The issue of voltage drop is an issue over distance with a small conductor but if it's sized right which it should be anyways it wont be an issue.