-1 color=blue>
« back to results for ""
Below is a cache of http://www.partsonsale.com/inverters.pdf. It's a snapshot of the page taken as our search engine crawled the Web.
The web site itself may have changed. You can check the current page or check for previous versions at the Internet Archive. Yahoo! is not affiliated with the authors of this page or responsible for its content.
NVERTERS 11th Edition Solar Electric Products Catalog May 2004
Inver ters
7 1
While an inverter can account for a good portion of the
cost of a PV system, it is really a sub-system that requires a
number of additional components. To make a safe, reliable,
code compliant installation one should provide the
following:
Inverter to battery cabling
Because of the high current required on low voltage
circuits, this cable is large, commonly #2 to 4/0 in size.
Smaller conductors than required are unsafe and will not
allow the inverter to perform to its full rating.
DC input disconnect and overcurrent
protection
It is important to have safe installation with a properly sized
DC rated, UL listed disconnect. Typically the disconnect
works in conjunction with an overcurrent protection device
such as a fuse or circuit breaker. These components are
usually installed in an enclosure which can also house
shunts and additional equipment or circuit breakers.
Shunts
Used to read the amperage flowing between the battery
and inverter, this device is installed in the negative
conductor. It can easily be housed in the disconnect or its
own enclosure.
AC output disconnect and overcurrent
protection
If the breaker panel, which is fed from the inverter, is
adjacent to the inverter, then the main breaker will serve as
the inverter output disconnect and overcurrent protection.
If, however, this panel is not grouped with the inverter, then
a separate unit should be installed. This also holds true for
AC circuits coming into the inverter from a generator or
utility source. A second breaker may be needed if these
breakers are not grouped.
I
NVERTERS
The inverter is a basic component of PV systems and it converts DC power from the batteries or in the case of grid-tie, directly from the PV
array into high voltage AC power as needed.Inverters of the past were inefficient and unreliable while todays generation of inverters are
very efficient (85 to 94%) and reliable.
Today, the majority, if not all of the loads in a typical remote home operate at 120 VAC from the inverter.Most stand-alone inverters
produce only 120 VAC, not 120/240 VAC as in the typical utility-connected home.The reason being, once electrical heating appliances are
replaced with gas appliances, there is little need for 240 VAC power.Exceptions include good-sized submersible pumps and shop tools
which can either be powered by a generator, step-up transformer, or possibly justify the cost of adding a second inverter.Several utility
line-tie inverters do produce 240 VAC.
Two types of stand-alone inverters predominate the market modified sine and sine wave inverters.Modified sine wave units are less
expensive per watt of power and do a good job of operating all but the most delicate appliances.Sine wave units produce power which is
almost identical to the utility grid, will operate any appliance within their power range, and cost more per watt of output.
Utility-tie systems / sine wave inverters for utility interactive photovoltaic applications, provide direct conversion of solar electric energy to
utility power with or without a battery storage system.These systems are designed to meet or exceed utility power company
requirements and can be paralleled for any power level requirement.They are listed to UL 1741 for photovoltaic power systems.
Inverter Component
Checklist
Batteries in Vented Enclosure
Inverter with Built-in
Battery Charger
Inverter
Breaker
Generator
Breaker
To AC
House
Panel
From
Generator
Inverter Sub-System Checklist
_____ Inverter to battery cabling
_____ DC disconnect and overcurrent device
_____ Inverter conduit boxes
_____ Inverter output breaker box
_____ Generator input breaker box
_____ Shunt(s) if required for monitoring
See the Sizing Tables in the
Appendix D for cable and
overcurrent device sizing for
the inverter you select. 11th Edition Solar Electric Products Catalog May 2004
72
Inver ters
Most larger
inverters can
operate as
battery
chargers as
well.This is
easily and
economically accomplished because of the design of most
inverters. Inverters step up low voltage DC power and change it
to 120VAC power. Battery chargers do the reverse of this.
Transfer switches are also incorporated into these Inverter /
Chargers so that the AC loads can be powered directly from the
generator when the battery charger is operating.
From a reliability, performance, and economical standpoint,
built-in battery chargers are the way to go.
Comparing Inverters
Inverters are compared by three factors:
Continuous wattage rating. Hour after hour, what
amount of power in watts can the inverter deliver.
Surge Power. How much power and for how
long can an inverter deliver the power needed
to start motors and other loads.
Efficiency. How efficient is the inverter at low,
medium and high power draws. How much
power is used at idle.
A typical 12-
volt lead-acid
battery must
be taken to
approximately
14.2-14.6 VDC
before it is
fully charged. (For 24 volt systems double these figures for 48
volt, multiply by four.) If taken to a lesser voltage level, some of
the sulfate deposits that form during discharge will remain on
the batterys lead plates. Over time, these deposits will cause a
200 amp-hour battery to act more like a 100 amp-hour battery,
and battery life will be shortened considerably. Once fully
charged, batteries should be held at a lower float voltage to
maintain their charge typically 13.2 to 13.4 volts. Higher
voltage levels will "gas" the battery and boil off electrolyte,
requiring more frequent maintenance.
Most automotive battery charger designs cannot deal with the
conflicting voltage requirements of the initial bulk charge and
subsequent float or maintenance stage. These designs can
accommodate only one charge voltage, and therefore must
use a compromise setting typically 13.8 volts. The result is a
slow incomplete charge, sulfate deposit build-up, excessive
gassing and reduced battery life.
The charger available in our inverters automatically cycles
batteries through a proper three stage sequence (bulk,
absorption and float) to assure a rapid and complete charge
without excessive gassing.
Factory battery charger settings on most inverter-charger
combinations are optimal for a lead acid (liquid electrolyte)
battery bank of 250-300 amp hours in a 70�F environment. If
your installation varies from these conditions, you will obtain
better performance from your batteries if you adjust the
control settings.
The Maximum Charge Rate in amps should be set to 20-25% of
the total amp-hour rating of a liquid electrolyte battery bank.
For example, a 400 amp-hour bank should be charged at no
more than an 80 -100 amp rate. Excessive charge rates can
damage batteries and create a safety hazard.
The Bulk Charge Voltage of typical liquid electrolyte lead acid
batteries should be about 14.6 VDC. There is no one correct
voltage for all types of batteries. Incorrect voltages will limit
battery performance and useful life. Check the battery
manufacturers recommendations.
The Float Voltage setting should hold the batteries at a level
high enough to maintain a full charge, but not so high as to
cause excessive "gassing" which will "boil off" electrolyte. For a
12-volt liquid electrolyte battery at rest, a float voltage of 13.2-
13.4 is normally appropriate; gel cells are typically maintained
between 13.5 and 13.8. If the batteries are being used while in
the float stage, slightly higher settings may be required.
Charge voltage guidelines used here are based on ambient
temperatures of 70�F. If your batteries are not in a 70�F
environment, the guidelines are not valid. Temperature
Compensation automatically adjusts the voltage settings to
compensate for the differences between ambient temperature
and the 70�F baseline. Temperature compensation is important
for all battery types, but particularly gel cell, valve-regulated
types which are more sensitive to temperature.
Built-In Battery
Chargers
Multi-Stage
Battery Charging 11th Edition Solar Electric Products Catalog May 2004
Inver ters
73
The STXR 2500 is designed, built and priced to make the benefits of site generated power easy
and affordable. Now anyone can install a solar array on their home or business to reduce or
eliminate their monthly electric bill while doing their part to reduce air pollution. To take full
advantage of this type of a system, net metering from your utility company would be a big
plus as it allows you to turn your existing kilowatt-hour meter backwards when your PV system
is producing more power than you are using.
The STXR 2500 incorporates all of the NEC and IEEE required AC and DC input/output
connections, disconnects