Why photo flash capacitors are rated at 55C ?

[LinuxHata]

Yes, I have read the wikipedia article and I do know, what is photoflash capacitor, in fact, I'm using them for maybe 20+ years

But I still can't understand, why 55C?

Making them 55C instead of 85C or 105C makes them cheaper? able to deliver more current? lower ESR or what?

I have repaired a lot of studio flash units and usually there is no cooling of capacitors - even if cooler is present, it either blows onto power circuitry, ballast resistors or tube itself, but very rarely - onto capacitors.

[mikeselectricstuff]

I'd guess  to allow headroom for self-heating from the high peak current in their normal operating conditions.

[Gyro]

Photoflash capacitors are specialised for really high energy density and discharge pulse current. I suspect that, if they were rated to 85'C, their lifetime spec would be unacceptably short.

[bdunham7]

But I still can't understand, why 55C?
I have repaired a lot of studio flash units and usually there is no cooling of capacitors - even if cooler is present, it either blows onto power circuitry, ballast resistors or tube itself, but very rarely - onto capacitors.

Well, how hot do they get then?

[LinuxHata]

Well, they usually get warm to touch, but nothing above that.
In most cases, they are mostly ok, except for situations where the unit is very old, say from late 70s, and they all dried out, or say, 110V unit was plugged into 220V mains. However, there are usually 2 or 4 "normal" capacitors (100uf, 450VDC most common) inside the studio flash, used in voltage multiplier circuit and these often get both hot and "pregnant" 

[DavidAlfa]

It the entire camera heats to 85°C you'll probably have worse problems than a shortened capacitor lifespan.... 

[alligatorblues]

Lower max temp caps can hold more charge, and flashes have temp protection circuitry to shut themselves down if necessary. That type of cap  also charges up quickly.