|
 UPS
(Uninterruptable Power Supply) units have been around for some time, particularly
with computer and network users. The need for clean, uninterrupted power has also
found its way into the area of home entertainment, particularly with products
such as video projectors that use very hot lamps. In addition, products sensitive
to line noise such as plasma displays can benefit from high performance power
products. Conventional power conditioners have been widely available for A/V electronics
from a variety of manufacturers, yet do little for brownouts (voltage sags) and
complete power outages. For many, this might not be a problem, but if you happen
to own an expensive LCD or DLP projector, you might have reason to be concerned.
It is certainly possible to damage the lamp or projector if power is suddenly
lost while the unit is running hot and doesn't have time to properly cool down
from its operating condition. As luck would have it, we had the opportunity to
review APC's Smart-UPS 750VA/480W (SUA750RM2U) rackmount unit, which was a good
match for our high definition DLP projector.
APC (American Power Company) has been making UPS units for over 20 years and targets
home/small offices, business networks, access providers, and data centers &
facilities. While this unit is geared more for networks and servers, it also provides
reliable power for moderate power needs. In addition, the Smart-UPS produces a
true sine wave instead of the modified sine wave version that produces undesired
harmonics. Weighing nearly 50 pounds, the SUA750RM2U is actually considered light
for a rackmount style UPS. The unit we reviewed here has the lowest power rating
in the Smart-UPS series family with the largest offering 5000VA/3750W and weighing
more than 200 pounds. We chose this unit primarily because we wanted a UPS capable
of supplying power to a DLP or LCD projector for sufficient time to shut it down
in the event of power loss. The Smart-UPS comes complete with rack mounting brackets
and support rails for standard 19" racks. Front
Panel
 The
front panel has separate On and Off buttons for power as well as
separate five-step indicators for the load and the battery supply capacity. The
Online indicator illuminates when the incoming utility power is available
to the UPS. The AVR Trim illuminates when the UPS is compensating for high
utility voltage and the AVR Boost illuminates when the UPS is compensating
for low utility voltage. If the UPS becomes overloaded the Overload light
will illuminate. The On Battery Power light turns on when the unit is running
on battery power and emits four beeps every 30 seconds to let the user know that
the battery is discharging. The Replace Battery indicator and Battery
Disconnected indicator are the same light, but emit different beeps based
on the problem. If the battery is disconnected, the unit will emit a beep every
two seconds. Upon powering the unit on, the Smart-UPS performs a battery test
to check the health of the system.  Rear
Panel
The rear panel consists of six protected outputs with a 10 amp circuit
breaker. Either a USB or an RS232 serial interface is used to communicate with
the UPS processor for setting parameters and getting status of the unit. We opted
to use the USB interface connected to our laptop. A red LED illuminates if there
is a problem with the incoming utility power. The long power cord was a nice addition.
The Sensitivity button has a green LED that changes intensity to reflect
the low, medium and high sensitivity setting. This chassis is also used for higher
powered UPS units which consume more power because the fan vent located on this
unit was unoccupied. If the user wants to have ethernet connectivity, the unit
has a blank panel revealing the SmartSlot used for the optional network monitoring
card.
Microcontroller-based
 The
inside of the Smart-UPS chassis holds a large circuit board that contains the
charging electronics for the batteries and the power inverter that converts battery
supply to full-wave 60 Hz AC. The Philips-based microcontroller sits in a socket,
making it easy to swap out in the event of a firmware upgrade. The processor is
responsible for monitoring the vitals of the unit and communicating with the USB,
RS232 and SmartSlot interfaces. The weight of the UPS is largely due to the heavy
lead-acid batteries installed in the removable tray and the large iron core transformer
used in the power inverter circuitry. The APC design appears to be quite efficient
and does not require a cooling fan to keep the electronics from overheating during
operation. 
Battery Pack
Two large 12VDC lead-acid batteries hold the power reserve
and are mounted on a removable tray that slides out of the front of the unit.
Four screws hold the tray in place. The slide-out tray makes it very easy for
a service technician to replace the battery pack even when the UPS chassis is
installed in a standard 19" rack. Additional battery packs are available
from APC through their website. A tethered rope tied to the cable connector allows
the user to quickly unplug the removable pack. The unit we reviewed had the batteries
wired in series with an inline 60 amp fuse for safety.
PowerChute
Software
 What
makes this UPS smart is the microcontroller contained within the unit. This combined
with APC's PowerChute Business Edition software gives the Smart-UPS powerful
monitoring capabilities. The version of software included
with the Smart-UPS is a basic 5-node edition of PowerChute that can be
upgraded to include more nodes. The software has three sections defined as Status,
Power Event Analysis and Voltage Analysis. The Status window
provides the Hostname, IP Address, Status, UPS Model, Serial Number, Firmware
Revision, Battery Replacement Date, Man Date, Location, Contact, Environment Monitor
(optional), Agent Version and Agent Operating System. Each of these items can
be enabled or disabled in the Configure Columns submenu or by right clicking
any of the columns on the table. The user can setup the software to check for
updates manually or automatically. 
The Power Event Analysis screen shows statistical data that characterizes
the incoming utility power. Events such as Power Failed, Low Battery, Extended
Undervoltage, Extended Overvoltage, Frequent Undervoltage and Frequent Overvoltage
are displayed over a period of time. The user can set the history to cover the
Last Day, Last 7 Days, Last 30 Days or Last Year.
This information can help determine if the threshold voltages need to be adjusted
to prevent the UPS from switching back and forth due to incoming power being marginally
high or low. In any event, the data is useful in determining problems.
 The
Voltage Analysis window displays the incoming voltage as a function of
time. Similar to a strip chart recorder, older data moves to the left as the new
data is updated. This allows the user to see the voltage history in the form of
a graph. The time displayed is selectable by the user (Last 30 Minutes, Last Hour,
Last 6 Hours, Last 12 Hours or Last Day). The High and Low Transfer
Voltages are user selectable and are displayed on the same chart. This makes
it easy to see if the incoming power is marginally close to the transfer voltage.
If so, it may be best to move the threshold point farther away from the incoming
voltage to prevent inadvertent tripping of the UPS unit. This is assuming the
electronics connected to the UPS can handle the voltage tolerance defined by the
user. Threshold values are changed in the Device Properties menu under
the Power Parameters section.
Device
Properties
In addition to the Power Parameters, the Device Properties
menu gives the user information about the UPS units connected to the network.
The Summary screen displays the general
information about the connected UPS including the Model Number and Serial
Number. The UPS Status screen
displays the current load on the unit and whether the UPS is running from utility
power or battery power. Also displayed here is the Internal Temperature,
Output Voltage, Input Voltage and Output Frequency. The Battery
Status screen shows the remaining capacity, Battery Status, Battery
Voltage, Runtime Remaining and when the battery was replaced. A
full Event Log is also provided with
the last event and time and date. The software is designed to monitor an entire
group of UPS unit(s) under a single program. PowerChute has the ability
to execute a command file before shutting down the operating system when a power
problem is detected. In this case, the user needs to specify the amount of time
required to run the command file. The system can send emails, pages and network
broadcast notifications.  Utility
Power
We measured the output voltage waveform from the Smart-UPS when
the unit was plugged into an active power outlet as well as when the power was
removed from the unit. In both cases the UPS was powering a 100-watt incandescent
lamp as a light load. Interestingly enough, we saw more waveform distortion when
connected directly to the utility power. The unit bypasses the internal power
inverter when the utility voltage is within an acceptable range. If the utility
voltage falls outside of the specified range, the UPS switches to the self-generated
120VAC. The top and bottom waveform peaks exhibit distortion. We are not sure
where this distortion was coming from, but it did appear in other places within
the house. Once the plug was removed from the wall and the UPS inverter kicked
in, the output waveform immediately looked clean.
Smart-UPS
Power
 As
the photo indicates, the waveform no longer exhibited obvious distortions. Unfortunately,
this UPS does not always supply AC from its internal generator, but instead switches
from utility power to the internal generator when power is out of range or lost
completely. There is also a short lag or dropout when this occurs which can affect
some equipment in rare cases. We tested the Smart-UPS with our DLP projector to
see how well the unit performed in real-world conditions. The Smart-UPS output
kept the DLP projector running giving us more than enough time to shutdown the
unit. Conclusion
The Smart-UPS is a nice design that provides true sinewave AC backup power to
connected components. While many switching power supplies work fine with stepped
AC waveforms, we prefer to keep the harmonics out of the powerline. We just wish
we had the AC generated from the Smart-UPS 100% of the time regardless of the
input. The PowerChute Business Edition software included with the unit
provides some excellent control and monitoring of the connected equipment and
is especially powerful at managing multiple UPS units when they are connected.
APC has also addressed the need for future maintenance by making it easy to service
the batteries once the unit is installed into a large chassis. The AC waveform
looked near ideal with our measurements and gave us confidence that our components
would survive a power outage. APC's optional web card ($299) further enhances
the capabilities of the unit with full ethernet connectivity. -
Kevin Nakano | 
