[BC] Cyberpower brand UPS

[Ron Youvan]

> All utilities in the US that are in any way connected to the grid, 
>are required by regulation to keep magnetic components, including generating equipment, 
>under 2 kG for 2% silicon steel equivalent, guaranteeing that the harmonic distortion 
>is under 1%.
/snip/

   I think harmonic problems are caused by nonlinear loads, non-resistive loads.

> However, many rectifier circuits draw current only on the AC voltage peaks, 
>creating lots of distortion. That is why there are now requirements for PF correctors, 
>which are really load correctors, so that harmonic power is not fed back into the power line.

   Transmitter power supplies (dc supplies) create a lot of harmonic energy.

  > Standby generators are not subject to regulation and, in the US; emergency generators
are not even required to be UL compliant! Emergency generators are things that are not
permanently connected, standby generators are, but do not need to be automatic.
  They both often use field coils that are too small for their rating, wound on magnetics
that are running at saturation, five or more kG, and rely on forced air from the engine
cooling to prevent them from burning up!

   Unless you buy junk, generators will supply a true sine wave into a linear load, not a sinusoidal 
wave, a sine wave.  Loaded with a DC rectifier supply the harmonic content of the building's power 
system depends on the impedance of the load and the impedance of generator.  The utility has a much 
lower source impedance than the small generator, so in the end that is why UPSs go nuts when you "go 
on generator."

   Sometimes putting a harmonic filter in front of the UPS is the easiest fix.  An expensive UPS 
will  already have one in there.  It is also there to keep the loads harmonics out of the buildings 
other equipment.

> Sizing a generator at a rating higher than the load requires does not help the 
distortion problem. This is because the rating of the magnetics has the dimension of
volt-seconds. The voltage per turn determines the field. The field varies inversely with
frequency and directly with voltage. The only way to determine if a generator you intend
to purchase has low harmonic content is to measure it. The vendor often does not know and
the manufacturer does not put it in the specifications.

   My supplier would not sell our 1.25 mW generator unless they supplied a 1.5 mW alternator because 
of my large nonlinear load.  I took their word for it.  (CAT)

-- 
Ron KA4INM