timer-switch contacts -load-bearing capacity

[AgX]

I am puzzled by the requirements stated for the Wallner 505.

The manual says:

max. 200W with halogen lamps driven by transformer
max. 500W with opal lamps driven on the mains

All halogen lamps driven by a transformer I can think of are switched at the mains side. The load situation on the timer switch thus is the same as with a opal mains lamp.
The mains voltage is the same for both cases, thus the max. current the switch can bear under that voltage is the same, thus the max. wattage should be the same too.
(Leaving aside the power consumption of the transformer itself, which should be deduced from the max. lamp wattage.)

I do not see an induction effect either.

 

[DWThomas]

Hmmm -- my first thought was inductive load. That typically puts more stress on switch contacts. But I know nothing about that specific unit -- is it truly just a simple transformer, or some fancy regulator circuit with an inductor and perhaps a non-trivial capacitor that could kick up surges and cause contact arcing. Just some late night speculation here ...

 

[AgX]

I just read-up on transformer switching currents (due to transformer core saturation), and they indeed can be in the range of 1-2 magnitudes above nominal current.


Is there such distinction at other enlarging timers?
Why do I not remember reading about this here before?

 

[ic-racer]

 

[ic-racer]

I just read-up on transformer switching currents (due to transformer core saturation), and they indeed can be in the range of 1-2 magnitudes above nominal current.


Is there such distinction at other enlarging timers?
Why do I not remember reading about this here before?

In the US, where Omega enlargers are manufactured, their halogen source enlargers were color enlargers and they had regulated power supplies with built-in triode switching (no relay as in the D5500). A halogen lamp with a simple transformer-only (and no voltage stabilization) would have been found on the older Omega power supply which came with its own appropriately spec'd timer which would handle the inrush current (Omega "Power Tower").

The third popular Omega circuit was used in the Chromegatrol which only had its own timer built-in, it used a constant voltage ferroresonant transformer which reduced inrush current.

I never saw a Durst use that type of transformer.

 

[AgX]

Mains voltage was rather stable in West-Germany at least, so the typical supply here for a low-voltage halogen lamp was just a plain steel-core transformer.
I meanwhile checked the manuals of the Kaiser enlarging timers, and there is no distinction on type of power supply of the enlarger, just plain max. Watts.

 

[Chan Tran]

Mains voltage was rather stable in West-Germany at least, so the typical supply here for a low-voltage halogen lamp was just a plain steel-core transformer.
I meanwhile checked the manuals of the Kaiser enlarging timers, and there is no distinction on type of power supply of the enlarger, just plain max. Watts.

Possible the rating is the limit of the transformer? as you are expected to use a specific transformer?

 

[AgX]

No, the Wallner 507 is just a (advanced) metering enlarger timer.
Back then it was the founding of the so-called Wallner Turret, consisting out of meter/timer, densitometer, colour-analyzer.

Wallner Turret (here with even more advanced meter/timer version 509 (w. 999 instead of 4 paper settings)