Output Current Monitoring
The AR-2330D’s ammeter reads AC current from 0 to 30
amps, in 3-amp steps. Currents above the 30 amp limit read red,
with yel low in di cat ing a warning zone. Please keep in mind that
the am me ter may not read at all if the total load connected is
less than 2 amps (240 watts). This is a likely oc cur rence if
only rel a tive ly low pow er, sig nal processing-type equipment is
connected. With the master switch off, the ammeter can still
read, but will only do so if equip ment drawing at least 2 amps is
connected to the un switched outlet.
The ammeter is capable of giving a re li able in di ca tion of
current drawn by all kinds of equipment, thanks to its true-RMS-
read ing circuitry. This means that loads like pow er amplifi ers, which
are primarily ca pac i tive and in duc tive, will read as accurately as
purely resistive loads like heaters. Ammeters that respond only to
average AC cur rent may vary widely from RMS reading meters.
Design
The AR-2330D uses a design based on an eight-tap toroidal
au to form er. The toroidal design assures minimal leakage of
stray mag net ic fi elds, and, because of its high effi ciency, a very
compact size for its rating. The Voltage Regulator’s circuitry mon-
i tors the incoming line voltage with each cycle, comparing it to
an ex treme ly precise voltage reference, accurate to ±0.15%. If a
voltage fl uc tu a tion requires that a different tap be selected, the
new tap is elec tron i cal ly switched ex act ly at the zero-crossing,
to avoid distorting the AC waveform. If nec es sary, it can switch
taps as often as once each cycle. Some com mer cial voltage
regulators using mul ti ple-tapped trans form ers switch taps at
uncontrolled times, there by cre at ing voltage spikes and clicks
that can leak into the audio! Hys ter e sis in the switch ing circuits
avoids “chat ter” or un nec es sary switch ing back and forth between
adjacent taps. And un like voltage regulators that em ploy
ferro-res o nant trans form ers, the Fur man AR-Series is not
sensitive to small er rors in line fre quen cy, making them ideal for
use with gen er a tors.
Supply Cable Wir ing
The AR-2330D’s rear pan el provides a NEMA
L14-30P male inlet connector; a NEMA L14-30 cord mount ed
fe male con nec tor is in clud ed with the unit. Please refer to the
“Rear View” wiring diagram at right.
Wire the two hot leads (black) to X and Y (black, and white or
red), and the equip ment ground (green) to G.
It is essential that all equip ment pow ered by an AR-2330D be
properly ground ed!
Never cut off the power cord ground pin or use a “cheat er”
adap tor on any of your equipment!
Installation
The AR-2330D is designed for mounting in a standard
19-inch rack. Because of its weight, the best position for it
is at the bottom of the rack. Its toroidal transformer minimizes
magnetic leak age, but nevertheless, due to its high capacity,
it can radiate an ap pre cia ble magnetic field. Therefore, we
recommend that it not be po si tioned adjacent to sen si tive, low
level signal processors, es pe cial ly mic preamps, mixers, tape
recorders, etc. Power amps may be more suit able “rack neigh-
bors.” As with any rackmount equip ment, be sure to use 10-32
machine screws for mount ing in the rack’s tapped holes, and to
avoid mar ring the front panel fi n ish, use plas tic wash ers un der
the screw heads.
Maximum Load
The AR-2330D can handle loads totalling up to 30 amperes
as long as the input voltage is equal to or above the selected
output voltage (240V). For voltages below that level, its ca pac i ty
must be derated at approximately .15 amperes per volt. See
Figure 2. To cope successfully with worst-case brown out
conditions, you should take this into account. An easy way to
calculate this yourself is to multiply input voltage by maximum
input current (ex. 200V x 30A = 6000 watts) to get the max i mum
pow er the unit can han dle at this input volt age. Then divide this
number by the out put volt age (6000/240 = 25 amps). If your load
draws any more than 25 amps, it will cause the input current to
rise above 30 amps and will then trip the break er.
Extreme Voltage Protection
The AR-Series includes special circuitry to sense over- and
un der-voltages and positively shut down the output before
possible damage is done. For the AR-2330D, overvoltages are
those over 300V. When the input voltage exceeds that limit, the
power will cut off. It will come back on automatically when the
ov er volt age is reduced to 285V or lower. The red LED labelled
EX TREME VOLT AGE SHUT DOWN in di cates the shut down
condition. The output is also shut down for extremely low input
volt ag es, less than 158V.
To provide additional protection against a catastrophic high
voltage condition, voltages over approximately 300V may cause
an in ter nal fuse to blow. This is a 250 mA/250V fuse and requires
removal of the top cover. If this unlikely condition occurs, please
remove power from the unit fi rst.
Fuses and Circuit Breakers
There are three fuses and one fast-acting magnetic circuit
break er in the AR-2330D.
1. A precision 30 amp magnetic circuit breaker is used as the
on/off switch. If the input to the unit exceeds 30 amps, the break er
will trip. Be sure to reduce your load before re-powering the unit,
or it will likely trip again. Refer to the previous section “Maximum
Load” if you are uncertain why the breaker is tripping, or want to
understand the relationship between input voltage and current vs.
output voltage and current.
2. A fast-blow 250 mA amp fuse is located inside the unit, as
previously mentioned. To replace it, the unit must be com plete ly
dis con nect ed from all power and removed from its rack. The six
hex head screws and one Allen head screw holding the top cov er
must be re moved.
3. A Fast Blow 1 amp fuse protects a low current auxiliary
wind ing on the large transformer.
Input Voltage Monitoring
The row of ten LED’s at the top left of the front panel make up
a meter that indicates INPUT VOLTAGE. Only one LED will light
up at a time. There are two red LED’s at the endpoints. When
lit, they indicate that the input voltage may be above or below
the point where it can be restored to the selected nominal output
voltage (though it may still be restored to a usable level) but is not
high or low enough to cause an extreme voltage shut down.
Output Voltage Monitoring
A green LED labelled OUTPUT IN REGULATION indicates
prop er function (i.e., that the output voltage of the selected out put
volt age is within ±10V of the 240V output. Your equipment should
work nor mal ly when this light is on, and often will work sat is fac to ri ly
even when it is off.
