– 42 –
When checking inverter voltage output, connect
the test-meter leads to any 2 of the 3 compressor
lead wires at the inverter plug (plug should be
connected). The same reading should be measured
between any 2 of the 3 wires.
The inverter controls compressor speed by
frequency variation and by Pulse Width Modulation
(PWM). Changing frequency and PWM will cause
an effective voltage between 80 and 230 VAC to be
received at the compressor.
• Low speed (1710 rpm) - 57 Hz
• Medium speed (2100 rpm) - 70 Hz
• High speed (3120 rpm) - 104 Hz
The inverter receives commands from the main
control board. The main control board will send
a PWM run signal from the J15 connector of
between 4-6 VDC effective voltage to the inverter
(all wires must be connected). The inverter will select
compressor speed (voltage output) based on this
signal.
The main control board will only send a run signal to
the inverter when the compressor should be on.
Note:
When measuring signal voltage (from the
main control board) at the inverter, a reading of 4-6
VDC will be measured with all wires connected. If the
inverter wiring is disconnected, the board output will
measure between 10-12 VDC.
The inverter will monitor compressor operation
and if the compressor fails to start or excessive
current draw (4 amps maximum) is detected,
the inverter will brie
fl
y stop voltage output. The
inverter will then make 12 consecutive compressor
start attempts (once every 12 seconds). After 12
attempts, if the compressor has not started, an 8-
minute count will initiate. After the 8-minute count,
the inverter will attempt to start the compressor
again. If the compressor starts, normal operation
will resume. If the compressor fails to start, this
process will be repeated. Removing power to the
unit will reset the inverter count. When power
is restored, the inverter will attempt to start the
compressor within 8 seconds.
The inverter has a built-in circuit protection to
guard against damage from a failed or shorted
compressor. However, if a failed compressor is
diagnosed, order a new compressor and inverter.
If the compressor fails to start after replacement,
replace the inverter.
Inverter Compressor
Caution:
Do not attempt to direct-start the
compressor. The compressor operates on a 3-phase
power supply. Applying 120 VAC to the compressor
will permanently damage the unit. It is not possible
to start the compressor without an inverter.
The compressor is a reciprocating, variable speed,
4-pole type. It operates on 3-phase, 80 to 230 VAC
within a range of 57 to 104 Hz.
Note:
Certain voltmeters will not be able to read
voltage output or frequency from the inverter.
Compressor wattages at various speeds are:
• LOW - 65 watts
• MED - 100 watts
• HIGH - 150 watts
The compressor is controlled by the inverter, which
receives its signal from the main control board.
Varying the frequency to the inverter changes the
compressor speed.
Compressor speed is based on the temperature
set point in conjunction with the speci
fi
c cabinet
temperature. Speeds are selected according to
the following cabinet temperatures, with freezer
temperature being the primary:
• 7°F to 19.5°F above freezer set point = high
speed.
• 4.5°F to 6.5°F above freezer set point = medium
speed.
• 1°F to 4°F above freezer set point = low speed.
• 1°F to 2.5°F above refrigerator set point = low
speed.
(
Continued next page
)
TA
B
1
J15-1 J15-2
AC
BROWN
BLACK
BROWN
COMPRESSOR
BLACK
BLUE
ORANGE
WHITE
RED
INVERTER
ORANGE
WHITE
RED
10
10
10
Main Control
Board
BROWN
