Rainlights/Pinspots on 100% Dimmers
- Thread startersoundlight
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Ship might be along later, but for the moment let me add my thoughts.
The fixtures in question are low voltage, with a transformer, correct?
If so, you can blow all your sums out the window. In an ideal world it would be fine, but ideal transformers simply do not exist. You are going to have significant power losses due to the transformer. In some instances I think that transformer can be as little as 50% efficient. So to power your 30 watt globe, you could be pulling as much as 60 watts of power. I think that transformers tend to be more efficient than that, but they are certainly no where near 100%.
I recall that in the past there was a discussion over the overrating of fuses. Just because a device has a 1 amp fuse does not mean that it draws a full amp. Manufacturers seem to like installing fuses of much higher value than they need to. It does mean that there is little chance of the fuse needing to be replaced but that comes at the price of protection. The higher rated fuse will not blow until the fault condition is more significant.
As for the inrush current, all incandescent loads will have a start up current, so it would be no different to say 2.4kW of say PAR56s in terms of startup current I would tend to think. Breakers will normally be able to tolerate this inrush, because it will only be for a short period of time, unlike say a discharge lamp where said inrush lasts several minutes.
Just some food for thought, hope at least some of it made sense.
The fixtures in question are low voltage, with a transformer, correct?
If so, you can blow all your sums out the window. In an ideal world it would be fine, but ideal transformers simply do not exist. You are going to have significant power losses due to the transformer. In some instances I think that transformer can be as little as 50% efficient. So to power your 30 watt globe, you could be pulling as much as 60 watts of power. I think that transformers tend to be more efficient than that, but they are certainly no where near 100%.
I recall that in the past there was a discussion over the overrating of fuses. Just because a device has a 1 amp fuse does not mean that it draws a full amp. Manufacturers seem to like installing fuses of much higher value than they need to. It does mean that there is little chance of the fuse needing to be replaced but that comes at the price of protection. The higher rated fuse will not blow until the fault condition is more significant.
As for the inrush current, all incandescent loads will have a start up current, so it would be no different to say 2.4kW of say PAR56s in terms of startup current I would tend to think. Breakers will normally be able to tolerate this inrush, because it will only be for a short period of time, unlike say a discharge lamp where said inrush lasts several minutes.
Just some food for thought, hope at least some of it made sense.
Me the expert on low voltage power? Na, that's voodo electric one step short of having to figure out DMX code or resistor code. I don't do enough of that kind of stuff to have any special expertise.
If the Pinspots are on stage dimmers, there will be little to no inrush current problems due to the warming current 7-20v the dimmer is already warming the filament with. Should be at 1/4 amp / 30w loading on the dimmers per fixture.
I normally figure on about 20% transformer loss at the most so say 1/3 amp or say a 36 watt loading on your dimmer. Two pinspot lamps per dimmer might be enough loading for them to function properly.
Are fuses below 1A readlly avalible at US voltages? The lowest fuse you normally see in the UK for mains is 3A (even in 75w fittings). Primarily due to the rarity of 1A fuses. Its fine so long as everything downstream is rated to or above the fuse rating. The fuse is really only there to stop the fixture (more realistically the cable) from catching fire in the event of a fault.
Fuses need to be spec'd to allow for the in-rush current when the device is first turned on. This is normaly higher then the operating current.
Different devices have different in-rush currents eg lights, amplifiers. Even in amplifiers the in-rush current can vary, apart from the amplifier rating, due to the transformer type. A toridal transformer has a bigger in-rush current for the same voltage and current ratings then the equivalent Laminated transformer.
Different devices have different in-rush currents eg lights, amplifiers. Even in amplifiers the in-rush current can vary, apart from the amplifier rating, due to the transformer type. A toridal transformer has a bigger in-rush current for the same voltage and current ratings then the equivalent Laminated transformer.
That's the correct design, in practice you would be amazed at how much latitude the final design uses in specing this stuff from a cost of bill of materials, but yes they certainly need to take into consideration what the maximum safe acceptable current requirement will be. In most cases, from a safety standpoint or even equipment protection, a variation of an amp or so is probably within acceptable margin
The designer will come up with a spec, and then the "value engineer" will work to get a practical low cost solution
Sharyn
The designer will come up with a spec, and then the "value engineer" will work to get a practical low cost solution
Sharyn
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