[ARC5] Vibrator Power Supplies

[J. Forster]

> Dynamotors typically have a conversion efficiency of no more than 50%. A
> vibrator supply can reach 70% easily, and often more, if designed
> properly. The modern day development of the vibrator is the switched-mode
> power supply, which often reaches in excess of 95% efficiency.
>
> I suppose when fuel was plentiful and cheap, what did it matter if you
> consumed a gallon to do a job that a quart could do?

Not so. Specifically, the WS 19 vibrator supply was considered a
significant improvement, because it required the AFV's engine to be run
far less to charge the battery. Patton's advance in europe was stopped
because of lack of fuel.

> Then you need to consider the downstream effects - the filtering
> components for a dynamotor are much smaller and lighter than for a
> vibrator, because of the frequency.

Also not so. The waveform of a vibrator supply is square wave like. Energy
storage in the filter can be much less than for a sine wave supply. More
filtering is required than a properly designed and adjusted dyno, but
nowhere near as much as a single phase line supply.

> But with SMPSUs, operating at 1 MHz or
> so, the filtering components are very much smaller than for a dynamotor.
>
> 73 de Brian, VK2GCE.

In general, the mass of iron required in a transformer is inversely
proportional to the operating frequency, if the peak flux density is held
constant. A rule of thumb is 40 Watts/pound for typical silicone steel.
However, as frequency goes up, so do eddy current (iron) losses. Ordinary
E-I cores, and even tape wound ones, crap out at maybe 5 kHz.

-John

==========
>
>
>
>> D C _Mac_ Macdonald <k2gkk at hotmail.com> wrote:
>>
>>
>> Transmitters used higher currents than receivers
>> and that may have come into play in some cases.
>>
>> However, as Richard Knoppow stated, they were
>> probably a whole lot more reliable for a demanding
>> application.  Motor and generator theory and practice
>> had been firmly developed and established for years.
>> About all that could go wrong were the brushes,
>> commutators, and armatures.  Look at how simple
>> it would be to change out the dynamotors on the
>> ARC-5 and SCR-274-N stuff!  They are also very
>> compact, if not particularly light weight.
>>
>> * * * * * * * * * * *
>> * 73 - Mac, K2GKK/5 *
>> * (Since 30 Nov 53) *
>> * k2gkk at hotmail.com *
>> * Oklahoma City, OK *
>> * USAF & FAA (Ret.) *
>> * * * * * * * * * * *
>>
>>
>> > From: 1oldlens1 at ix.netcom.com
>> > To: releazer at earthlink.net; arc5 at mailman.qth.net
>> > Date: Fri, 7 Dec 2012 08:17:01 -0800
>> > Subject: Re: [ARC5] Vibrator Power Supplies
>> >
>> > ----- Original Message -----
>> > From: "Robert Eleazer" <releazer at earthlink.net>
>> > To: <arc5 at mailman.qth.net>
>> > Sent: Friday, December 07, 2012 5:35 AM
>> > Subject: [ARC5] Vibrator Power Supplies
>> > > Two questions:
>> > >
>> > > 1. Why did they not use vibrator power supplies instead
>> > > of dynamotors in WWII? They ought to be cheaper and
>> > > easier to build.
>> > >
>> > > 2. I have the transformers out of an old RCA Carfone
>> > > vibrator power supply. Tried to make a DC power supply
>> > > out of them. They do not work all that well with 115V
>> > > 60Hz on the secondary. Anyone know why?
>> > >
>> > > Wayne
>> > >
>> > I think because dynamotors may have been more reliable
>> > and also put out more nearly pure DC.
>> >
>> >
>> > --
>> > Richard Knoppow
>> > Los Angeles
>> > WB6KBL
>> > dickburk at ix.netcom.com
>>
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