[ARC5] Receiver AC Power Supplies

[Fuqua, Bill L]

  Don't forget, there are I squared losses in the primary as well.
73
Bill wa4lav

________________________________________
From: ARC5 [arc5-bounces at mailman.qth.net] on behalf of Brian [brianclarke01 at optusnet.com.au]
Sent: Friday, December 12, 2014 11:24 PM
To: arc5 at mailman.qth.net; hwhall at compuserve.com
Subject: Re: [ARC5] Receiver AC Power Supplies

Not quite Wayne,

Use a CRO to look at the output from either FW or FWB, before any filtering.
In both cases you will see exactly the same waveform, and hence, the
transformer's duty cycle. But measure the current in the separate windings
with a CRO to see each winding's duty cycle. Then you will see a duty cycle
of 2, not 4, if the primary and secondary windings and the core are up to
it.

Labelling for major manufacturers is the work of the marketing department,
not the designer. So, your last sentence does not indicate anything that
would stand up in an EE classroom. The only simultaneity is in the guile of
the PR people and the gullibility of the buyer.

73 de Brian, VK2GCE.

On Saturday, December 13, 2014 3:06 PM , Wayne said:

<snip>
>duty cycle - this last bit you seem to have missed

You're right, I did overlook that. So... if the load current doubled then
the ohmic loss goes up by a factor of 4. But in changing from a bridge
(current flow nearly fullcycle in full winding) to a centertap fullwave
(current nearly halfcycle in only half the windings at a time) the total
duty cycle in all windings is reduced by factor of 4. A wash on average
(ignoring other factors that might play in reality but aren't known in the
discussion). Did I get that right?

>A transformer rated at 25 V and 2 A, may not be designed to deliver both at
>once.

Good point. Most of the transformers I've used were labeled as "xx volts at
yy amps" indicating simultaneous ratings.

Wayne
WB4OGM

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