[time-nuts] No more 60Hz, How do I discipline 120VAC 60Hz from a UPS
albertson.chris at gmail.com
Sat Jun 25 17:25:34 UTC 2011
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
Redondo Beach, California
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