INVERTER SHUTDOWN
The compressor may only be switched off by
cutting its power supply or by entering the due
speed control input.
If the compressor is make to stop due to power
supply switch off, then the inverter will self reset
when the power is recovered and begin a new
starting procedure.
If the inverter remains connected to AC line
while the compressor is stopped, a stand by
power consumption will be present in order to
maintain the inverter in operation.
PROTECTIONS
The VCC compressor is electronically protected
meaning that this function is performed by the
inverter circuit during its operation. The
compressor itself is not equipped with internal or
external conventional overload protector
(bimetallic). The following are the main built in
protections and performed by the inverter.
a) LOW OR NO VOLTAGE – If the AC
(supply) voltage drops below 85 VAC
(as a general rule) the inverter will be
automatically reset.
b) “WATCH DOG” – A “watch dog”
routine running at all times will reset the
inverter in case strong line or control
signal disturbance occur. The “watch
dog” function provides a hardware
monitor over the software to avoid
losing the program. All the signals that
the microprocessor is receiving are
monitored.
c) LOCKED ROTOR – In case the rotor is
locked during the starting trial, the
current output to the compressor is
interrupted. In the occurrence of a
failed start, a limit of 12 consecutive
tries will be made until the inverter will
assume a waiting condition depending
on the software version installed (this
situation may be encountered if there is
no equalized pressure between suction
and discharge sides in the refrigerating
system.
d) HARDWARE CHECK –During the
starting procedure and before applying
current to the compressor motor, all
power switches are checked for short
circuit. If a malfunction is detected, the
inverter will enter the waiting time
mode.
e) OVERCURRENT PROTECTION –
The inverter hardware is able to detect
and react when the current overcomes a
predefined limit of 3.3amps. In case the
input current limit is reached, the motor
current will be kept at this value.
f) OVERLOAD PROTECTION – If the
load on the shaft of the compressor is
increased for a given speed input, the
current will be increased until its limit
(3.3 A max) is reached. If the current is
already at 3.3 Amps then the speed will
be decreased until constant speed is
achieved keeping the balance with the
shaft load. If the load continues to
increase the compressor will reduce its
speed until the lowest speed limit. If the
load is further increased then a stall
condition is reached.
In case the overload is kept for a long
time, the power stage of the inverter
may increase in temperature. This
overheating is then sensed by a
temperature sensor installed on the
power switches heat sink that shuts
down the inverter when over the limit of
90° C.
g) SPEED PROTECTION – Two
operating limits are defined for the
compressor operation: Min speed 1600
rpm (53 Hz) and Max speed of 4500
rpm (150 Hz).
a.
Minimum speed: if the speed
signal requires operation under
the speed limit than the
compressor
will stop.
36
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