[ARC5] Vibrator Power Supplies

[Brian Clarke]

Hello Wayne,

Transformers up till about 1960 had rather poorer steels than we have 
nowadays. So, the hysteresis curve was much fatter; this meant that more 
energy went into heating the core, particularly if the Voltage rose. So, to 
handle mains surges and dissipate the heat, manufacturers in those days 
designed bigger transformers. Nowadays, accountants have become transformer 
designers and so, transformers are flatter to reduce the magnetic path 
length, and run the copper at over 3000 A / sq in. So, modern transformers 
run hotter and burn out sooner.

Generally, you can select an input Voltage almost directly proportional to 
the operating frequency. So, in Australia where the mains is 50 Hz, an 
American piece of equipment cannot be fed more than 5/6 x 115 = 95 Vac, 
which then has a direct effect on the available secondary Voltages. I find 
it strange that Americans 'on loan' over here bring all their heavy white 
goods and connect them to simple Voltage converting transformers and then 
wonder why stuff burns out. Perhaps the US embassy doesn't give out such 
advice.

We face a related problem in Australia. Our new (since 2000) standard mains 
Voltage is 230 V. But for the last century, it was 240 V. So, the standard 
has been re-written to have a higher plus tolerance to cater for when you 
are at the end of a distribution line. Then, of an evening when all the 
cookers get turned off, and before the distribution transformer tap changers 
take effect, the Voltage rises to 265 - 275 V. The Europeans that have 50 Hz 
mains have 220 V as their standard. European goods imported into Australia 
will invariably burn out their transformers, unless the importer changes the 
transformer before sale - but that negates the benefit of importing cheaply 
from Europe, so, it doesn't happen. The customer pays ... and pays.

73 de Brian.

----- Original Message ----- 
From: "Robert Eleazer" <releazer at earthlink.net>
To: <arc5 at mailman.qth.net>
Sent: Saturday, December 08, 2012 10:51 AM
Subject: [ARC5] Vibrator Power Supplies


>I have a 1945 Aviation Magazine that has a full page color ad touting a new 
>innovation: vibrator power supplies.
>
> Also note that the lower iron in higher frequency transformers affects 
> what voltage the transformer can handle at lower frequencies.  Lower 
> frequencies, then lower voltage is allowed.  I am using those transformers 
> at what I assume is 1/2 their normal operating voltage in their 
> secondaries: 125VAC rather than the 250V I assume was the norm.
>
> And they are big heavy beasts.
>
> Wayne