Re: Run 415 V machines on 480 V?

On Sun, 7 Aug 2005 17:44:36 +0000 (UTC), Christopher Tidy
<cdt22NOSPAM@xxxxxxxxxxxxxx> wrote:

>snip
>Thanks for the advice. Out of curiousity, why is the primary
>traditionally wound closest to the core? This transformer is tempting,
>but my concern is that the "official" voltage in the UK is 415 V, so I
>will be supplying a somewhat excessive voltage to the motors. What do
>you think?
>
>> I asume that you are more comfortable with 480 vac than I am. I hate
>> 480.
>
>I'm pretty careful. I only ever once had a shock, and that was off a
>capacitor which had held a charge for a while. After that I was very
>wary of capacitors.
>
>Chris

It's more than tradition. The winding closest to the core has
the shortest mean turn length so the copper loss of an inner winding
is less than that of an identically wound outer winding.

Best efficiency occurs if the winding handling the highest
power (the primary) is the inner winding.

Because this results in the lowest total copper loss it also
yields the best voltage regulation.

Power transformers are efficient devices and it's usually OK to
use an outer winding as a primary and accept a pretty minor drop in
efficiency.

However it reverses the design corrections for the voltage drop
resulting from winding resistance. This will alter the apparent full
load voltage ratio. For example:-

With 1% copper loss in an inner winding and 1 1/2% copper loss in an
outer winding a 1:1 full load rated transformer would need 2 1/2%
extra turns on the secondary to compensate for the voltage drop.

If this outer winding is now used as a primary the OPEN CIRCUIT
output voltage is now only 97 1/2 %. The full load voltage drop will
reduce this to 95% so that the nominally 1:1 transformer is now only
1:0.95

Perhaps a more useful way of assessing this is to allow for a
voltage error of twice the rated no load to full load voltage drop

Jim
.

Relevant Pages

  • Re: Driving LEDs with a battery pack
    ... Note that nowhere in the above equations is the transformer ... It's being used to boost the battery voltage as seen by the base ... rate of flux change that is 'seen' by the base winding as aiding the ... I'm short on these green LEDs, ...
    (sci.electronics.basics)
  • Re: 5B 255M amplifier?
    ... I presume you mean the heater voltage bump on the PC Speaker Hybrid ... task of winding them it will work out about twice the price of a pre- ... couple on an amp he built, check out his web sitehttp://members,aol.com/sbench101/. ... I did use a power transformer for OPT on the 6CW5 guitar amp, though, ...
    (rec.audio.tubes)
  • Re: Flyback regulator / transformer problems.
    ... I have essentially the same cct with a different transformer, and feedback components changed for a 5Voutput.The other outputs are not regulated, I have only wound the 5V winding and populated the pcb with the required components for 5V out so far. ... The drain voltage of the FET is going WAY to high.Up to about 800V spike. ... The switching frequency is about 100KHz.I am using a EC35 core with N27 material with a 0.5mm gap. ... drive gate with pulse generator at about ...
    (sci.electronics.design)
  • Re: DC magnetisation of transfromers and chokes.
    ... V is the voltage in Vrms across the winding, ... Afe is the core area in sq. ... Is µe just µ with ungapped material? ...
    (rec.audio.tubes)
  • Re: Transformer drawing 1 amp
    ... When there is no secondary load, the inductance of th ... precipitously, twice a cycle, if the core flux reaches ... This occurs if you apply excessive voltage to ... The transformer limits current to the secondary by the ...
    (sci.electronics.basics)
Loading