Re: [CAD_CAM_EDM_DRO] Re: Center tapped transformer

Both coils are supplying power during each half cycle,
using a FWB. The CTB only pulls power from one side of it's
coil at a time. I did specify that one had to be able to
'split' the c.t. into 2 separate windings, and 'parallel'
them. Also, the voltage is then 1/2 of the full c.t.
voltage arrangement, but you should be able to draw twice
the current. The secondary winding will supply whatever you
draw on it for power, up to it's rated capacity (actually,
beyond it, depending on how it's designed). If you have a
resulting 36Vdc supply, and a 36 ohm resistive load, you
will draw 1 amp dc, a total of 36 Watts, even if the supply
is capable of delivering 108 Watts (36Vdc at 3 Amps).
Actually, if the supply *is* rated for 108 Watts, the
36V/36Ohm combination will likely draw slightly more than 1
amp, due to 'regulation' of the secondary output, which
will likely be slightly higher than 36 Vdc.

This is may be treading on O.T., perhaps we should retire
to the 'lounge'.

RayHex

----------

> From: caudlet <tom@...>
>
>
> --- In CAD_CAM_EDM_DRO@y..., "Raymond Heckert" <jnr@a...>

wrote:

> > Tim, You should expect double the amperage at half the
> > voltage, if you can split the center tap secondary into

two

> > isolated windings and use a FWB. Just connect the start

to

> > start & finish to finish on the secondary. Even if this

is

> > bi-filar wound (not real likely), the voltage is low
> > enough, not to worry about breaking down the wire
> > insulation.
> >
> > RayHex
> >
> How would that be different than grounding the center tap

and using

> two diodes? Using the centertap approach, each side of

the winding

> supplies half of the power. "Watts is watts".

Transformers are

> designed to transmit power. The total amount of power is

determined

> by the amount of power (I*E) coupled from the primary to

the

> secondary through the magnetic field less any losses in

the core and

> windings. With a given size and type of magnetic core

and a given

> number of turns in the primary of a fixed wire size, you

can only get

> a defined number of watts from the secondary. The ratios

of voltage

> to current change, but to maintain the same load on the

transformer,

> the total wattage has to remain the same.
>
> In a common center tap configuration the positive section

of the sine

> wave is transformed by one half of the winding and

rectified by one

> of the diodes. During the negative transition of the wave

the other

> half of the winding does positive in relation to the

center tap and

> performs the other half of the rectification process.

You end up

> with each side supplying 50% of the average current at

half of the

> full winding voltage. This maintains the basic total

wattage

> concept. Since heating and losses in a conductor are a

factor of

> resistance AND duty cycle, each conductor carrying 2X the

current for

> 1/2 the time is equal to two parallel windings carrying

1X the

> current for 100% of the time. There are some other minor

factors

> that do not make the two methods EXACTLY equal but they

are on the

> order of 1% or less. Power transformers are not precision

devices

> anyway. To get the lower voltage,technically you could

use just the

> center tap and one leg into a full wave bridge and keep

PRIMARY

> wattage the same, but your secondary winding losses would

go up and

> depending on the wire size of the secondary might start

to overheat.

> (Remember that the losses are I^2 * R) Average losses

(heat)are

> factored over time.
>
>
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