Re: [A/S] Honda EU2000I Generator(s)

["Don" <dash7_@xxxxxxxxxxx>]

Hi Jim and Wayne, 

Perhaps I can shed a little light on your questions from a 
theoretical perspective. As I mentioned in my last posting, I am not 
familiar with the Honda EU series, my experience is with airborne 
equipment, but the concept should be similar.

Typical "portable generators" (actually alternators} are an
engine driving an alternator producing an AC output whose frequency 
is dependant on engine rpm. The engine is controlled by a governor 
that forces it to run at a specific rpm.

The Honda EU2000I is actually a composite power generating system 
composed of an engine/generator and an inverter and because of the 
electronics involved, it doesn't have to play by the same rules
as the traditional portable power plants.

(I'm taking some liberty with the terms used here in an attempt
to keep the explanation brief.)

A typical simple inverter, which takes direct current (DC) and 
converts it to alternating current (AC) is composed of a chopper, a 
driver, a transformer and an output circuit.

The DC input goes through the chopper, which is nothing more then a 
switch being turned on and off by a clock.  This "chops" the
dc into 60 hz pulses, creating AC which is sent the driver circuit.

The AC goes through the driver to the transformer, which steps the 
voltage up to 115 volts and sends it to the output circuit 

The output circuit monitors the voltage from the transformer and 
sends a control signal back to the driver circuit to maintain 115 
volts. The output circuit also monitors the output current (power) 
and in some inverters, if it exceeds design limits, the driver is 
shut down, protecting the inverter from damage.

Two inverters running in parallel are connected together by a cable, 
a "synchronizing" circuit and an "output balance"
circuit.  The cable performs several functions including determining 
which inverter is #1 and which is #2.

One end of the cable will connect to the output of an inverter's 
clock.  This becomes the #1 inverter.  The other end of the cable 
will disable the #2 inverter's clock and substitute the clock
signal from the #1 inverter.  Now with the choppers in both inverters 
controlled by the same clock, their outputs will be the same 
frequency and the same phase.  With each inverter's output
circuit controlling their respective unit's voltage at 115 volts, all 
of the "synchronizing" requirements are now satisfied and the
inverter outputs can be tied together.....paralleled.

(In the above example, it would be necessary to start the #1 inverter 
first because the #2 inverter's clock is disabled.  With it's
clock disabled, starting #2 inverter first could result in an 
uncontrolled AC output that might damage the inverter or a load 
connected to it.) 

The "output balance" circuit receives and compares
information from the current monitor in the output section of each 
inverter.  If the currents are not equal, a command signal is sent to 
one or both inverters to balance the current while maintaining the 
same total power output.

With the engine/generator producing DC for the inverter input there 
is no longer a requirement for the engine to run at a specific rpm.  
It can now be throttled back to produce only enough power to satisfy 
the load requirement at the inverter output, resulting in fuel 
savings and, maybe more important in RV use, a lower noise level.

Don (MI)