[time-nuts] No more 60Hz, How do I discipline 120VAC 60Hz from a UPS

Will Matney xformer at citynet.net
Sat Jun 25 17:48:56 UTC 2011


That's close to what I did, but I think the chips output to the switching
transistors was a modified squarewave, made to act like a sine wave, where
the waveform is stair-stepped. One could use a plain 60Hz crystal
controlled oscillator, and start out with push-pull amplifier stages to get
to the final switching power you need, the same or similar as building up a
push-pull transmitter.

The reason for using 12 Vdc, is that you can pick them up, and 24 Vac CT
transformer, on the cheap, with quite high power ratings. Any switching
types like this do require extra power which is expended in heat, and you
would have to calculate those losses for the main DC supply transformer.
Motorola had an application note on doing this in their catalogs around
1965-1970. That was back in the time of the large Ger. switching
transistors too.



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On 6/25/2011 at 10:25 AM Chris Albertson wrote:

>On Sat, Jun 25, 2011 at 9:50 AM, Don Mimlitch <donmeis at yahoo.com> wrote:
>> I collect clocks an have many clocks with 60Hz Synchronous Motors.
>> How would I go about Disciplining a 60Hz 120VAC source from an
>> Unintteruptable Power Supply (UPS)?
>Most comercial UPS are quite crude.  Theu make square wave AC.  In
>your case, I think the way to go is to build a precision 60 Hz
>oscillator .   It can be very low power and work at 5 volts.   I would
>deriv the 60Hz from a 10Mhz reference, either devide it down then
>drive a PLL or use a DDS chip.    Filer it then usethis precission
>60Hz signal to feed something that looks a lot like an audio
>amplifier.   This kind of design is expensive if you need many watts
>but you clocks likely don't need many watts.
>The amplified can run from a high voltage DC source.  As (I assume) we
>don't care about efficiency you can drive the amp with a 200V DC
>linear supply like you'd find in a tube based amp.   the feedback loop
>of the typical audio amp is replaced be an an AC voltage comparator.
>Feed back drive the output to exactly 120V.
>Use a different design if you care about power consumption and waste
>heat.  The above is a simple "on line" supply.   A comerical UPS like
>this is more complex and uses a SMPS for the high voltage and runs the
>SMPS from a battery that is also being charged from AC mains.   These
>use a crystal for a freq. reference.   You might just buy one and
>replace the crystal with a DDS drive from your 10Mhz reference.  But
>these comercial on-line units are not cheap like home computer backups
>Chris Albertson
>Redondo Beach, California
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