SW4024 switching issue [RE-wrenches]

[William Miller]

Pals:


At 09:15 AM 2/7/01 -0800, you wrote:
>Kurt:
>
>Transfer &
>genny shutoff occur simulateously on every inverter I've installed w/ 4.01.
>Conclusion: vaporware. Maybe it's in 4.1. - but I'm probably dreaming.
>Kirk
>

It has been my consistent experience that an SW inverter (V4.01)
controlling a generator, when in automatic mode will transfer away from the
generator some time prior to stopping the generator (40 seconds sounds
about right).  Now, if you have two inverters stacked, the second inverter
does not act this way.  The inverter not controlling the generator does not
know the generator is about ready to be stopped so it does not transfer
prior to generator stop.  Watch the green AC2 in LEDs while this cycle is
happening and you will see the SW controlling the generator will begin to
flash after the load is transferred away from the generator while the LED
on the other SW remains solid.  The flashing indicates the generator is in
cool down.  Could it be that the appliances that are resetting are powered
by the non-generator-controlling inverter?

The Trace manual claims the SW inverters (and I believe DR series, for that
matter) can transfer power quickly enough to be classified as UPS units.
This is complete Hogwash.  Anyone can see the lights flicker during
transfer and during load level changes.  A small inverter system such as
these does not have the inertia required to maintain proper voltage
regulation for running micro-processor based appliances.  I tell all of my
clients that having a battery powered inverter system does not mean you
don't need a UPS, it just means you need a smaller one (less batteries for
less required backup time).

I have a client who is a glass blower.  He has an AC powered solenoid that
will shut off his furnace in the case of a power outage.  This is necessary
because a blower is required to operate while the furnace is running.  His
SW system would not hold the solenoid during transfer.  I installed a UPS.
It would not hold the solenoid (this bugger is fast!).  We invented a
system to resolve the problem, but this underscores the fact that a SW
system does inevitably have transfer switching artifacts.

William


__________________________________________________________________
William Miller
SLO Communications: Communications and Power Systems Consulting
Chief Engineer, KCBX: NPR and PRI for San Luis Obispo and Santa Barbara
PO Box 50, Santa Margarita, CA 93453
Voice :805-438-5600		Fax: 805-438-4607	VMail: 805-546-4875
email: wrmiller at slonet.org
License No. C-10-773985
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