Putting UPS's in series?

On Tue, 01 Jun 2010 18:45:10 -0400, LSMFT wrote:

YKhan wrote:
I'm wondering if there are any dangers or precautions to putting a
couple of UPS's in series to increase their power-on time?

Yousuf Khan

Series would double the voltage and blow your stuff up.

That's funny. I hadn't thought of connecting the OUTPUTS in series.

Sam E wrote:

On Tue, 01 Jun 2010 18:45:10 -0400, LSMFT
wrote:

YKhan wrote:
I'm wondering if there are any dangers or precautions to
putting a couple of UPS's in series to increase their
power-on time?

Yousuf Khan

Series would double the voltage and blow your stuff up.

That's funny. I hadn't thought of connecting the OUTPUTS
in series.

In 'normal' mode, most consumer-grade UPS devices just pass
through the input mains power. Any attempt at connecting the
outputs in series would either result in total output
voltage equaling mains voltage, or zero and an immedite
shutdown by either unit's short-circuit protector.

When operating off-line (i.e., during a line power failure)
it would be possible to obtain much more than rated voltage
with the series connection, but it would be weird. The two
UPS units would not be phase synchronized and probably would
not even operate at exactly the same frequency. Output
voltage would vary unpredictably.