Re: [tlug] [OT] Taking appliances between J and US power

[Jim <jep200404@example.com>]

The two most favorite words of a consultant are: 

   "It depends."

"Godwin Stewart" wrote: 

> ..., there isn't much point in using a transformer to step down
> from 110V to 100V. 

That depends on the kind of device and what it was designed for. 
Keep in mind that Iannucci reported overflow suds on "110v" power. 

My 100 VAC suihanki works perfectly at 100 VAC 
and consistently burns the rice a bit at 120 VAC. 

For most devices, reduced voltage means reduced power consumption, 
so during power shortages, the electric companies will reduce the 
voltage, to reduce the power consumption. 

However, some devices consume _more_ power at lower voltages. 
Induction motors designed for 110 VAC to 120 VAC, 
on 100 VAC it will draw more current (and run hotter!) 
and so is stressed by lower voltages. Motor failures rise 
dramatically during such "brownouts". 

For typical PC switching power supply, like many of us use to run 
Linux on, the power consumption is mostly constant with regard to 
line voltage variations. I would expect a modest _increase_ in power 
consumption for decreased line voltage and modest _decrease_ in power 
consumption for increased line voltage. 

I seem to recall mention on this list of some (laptop?) computer power 
supplies not coping well with 100 VAC in Japan. 

Also keep in mind that the nominal voltage for most of North America 
is 120 VAC, not 110 VAC. For resistive devices, a 10% increase in 
voltage yields a 21% power increase (ignoring increased resistance) 
and a 20% voltage increase yields a 44% power increase. 

> Equipment bought in the UK, where the voltage is
> 240V, works fine in continental Europe, where the voltage is 220V, and
> vice-versa. Such small differences in voltage are peanuts to an
> appliance, especially as your mains voltage is liable to swing that much
> anyway - it can vary by 10% either way of the nominal voltage.

Again, depends how it was designed. Most will tolerate 10% variation. 

> If the transformer is okay the appliance will run on 100V no problem.

Certainly so for the 100VAC suihanki. For other appliances, it depends.