Allowable studio flash current (A) requirements

I'm seeking for some practical experience with the maximum allowable Amperes (2 second pulse) one can draw without blowing a fuse in what I believe to be an average European setting (230V 50Hz, 16A fuse per group).

In particular, I acquired 3 Multiblitz Xenolux 1000 monoblocks. These each draw a 10A current on recharging, but with the limited testing equipment I have I can only detect that for a period of less than 2 seconds.

Does anybody have (first hand) experience if that is too much to ask from the normal 16A power groups that one finds on many home locations in my country? I can test it for my location, but I intend to use this mobile set on various other locations as well, so some user experience might help, before I build my own the hard way. I would rather not learn from experience that it might cause serious problems in say monumental mansions, or at best the replacement of a fuse or two (=embarrasing).

Liability insurance is expensive enough without seeking for trouble ...

Bart

Hi Bart,

It will depend on the characteristics of the fuse, of course, and it may be entirely different if mniature over current circuit breakers are used instead of fuses. It would be safer to recharge the flashes individually, if that is possible. A very, very rough rule of thumb is that a fuse can carry, say, twice its rated current for ten seconds, but it depends on its age, etc. It is not just the fuse that can give problems, however. If there is a switch iin the circuit that is on its last legs, then you you may end up welding the contacts closed.

In theory, you should be OK for a few shots, but there are too many unknowns to be able to give a practical answer.

Best wishes,

Ray

Ray West said:

It will depend on the characteristics of the fuse, of course, and it may be entirely different if mniature over current circuit breakers are used instead of fuses. It would be safer to recharge the flashes individually, if that is possible.

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Ray, thanks for your thoughts.
Yes, I am referring to regular fuses rather than miniature circuit breakers.

I'm also looking at the usefulness of a circuit load interruptor/distributor, the type used for washing machines + dryers that switch of the dryer while the water heater is on, but I don't know how fast they switch. Afterall it's just, say, a 2 second 10A peak current per monoblock, before it falls back to 0.07A without or 2.6A with modelling lights at maximum power each.

A very, very rough rule of thumb is that a fuse can carry, say, twice its rated current for ten seconds, but it depends on its age, etc. It is not just the fuse that can give problems, however. If there is a switch iin the circuit that is on its last legs, then you you may end up welding the contacts closed.

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Yes that's my assumption as well, which I can test empirically, but I thought it might be useful (not only for me) to gather some statistics about what experiences people might have or what information sources are available. So I hope a few others will chime in as well.

Bart

Hi Bart,

If you wanted to build some sort of sequential switching unit, then three solid state relays, and a controller - I'd use a PIC or similar micro p, would be pretty simple to set up, if it is suitable to switch purely on a timed basis. For two seconds - say three to be safe, then ordinary electro mechanical relays would suffice, at less cost. Of course it would slow down the overall cycle time of the flash system.

The sequence being, say - power up flash unit 1, wait three seconds, power up flash unit 2, wait three seconds, power up flash unit 3, wait three seconds. it then - simple solution - powers off all units, until you press the 'controller's charge button', when the sequence begins again. A more automatic unit could use a photo transistor to initiate the charging cycle, and power could be maintained until the first flash unit fires. (I need to think that through a bit more... modelling lights....)

A more complex solution could monitor the current, and only power up the next flash when the line current has dropped below 5A, say, but this would cycle the system quicker.

In most of the above, I am assuming that power does not need to be maintained to the flash until it is triggered. If when it is triggered, it immediatly starts to recharge, then it will be a tad more complex to prevent that happening.

If you wanted to go this diy route, then I would help you get there, but due to CE conformity requirements, I would not be able to build you a complete cased solution ( but could supply a kit...)


(In the Uk, we have a 'ring main system', limited to 13A per outlet (fused plug, fused to protect the load/flex), but being a ring main, provided there is no other load, we could simply plug each flash into a separate socket, without blowing the main fuse - if its the correct value (generally 30A, or 32A mcb). I wonder what fuses first in a radial system, a 16A fuse, or the 5A flex to the table lamp??)

Best wishes,

Ray