Fairbanks Nijhuis™
11/12/12
Intelliboost™ Water Booster System
Basic Operation Manual
16
4. Check the tightness of connections.
a. Loose power connections can cause extra heating and/or arcing. The heating reduces efficiency and can
actually melt down connectors. The arcing can cause intermittent currents and electrical noise. These can
disrupt the operation of the drive.
b. Loose or corroded ground connections can cause electrical noise problems. All of the VLT drives have some
degree of electrical noise filtering. Some of this electrical noise is sunk to earth ground. Without a reliable ground
connection the noise filters cannot operate as designed. In addition, a poor ground connection can become a
safety issue.
c. Loose control wires can cause intermittent operation of equipment. Loose or missing shielding for signal wires
can cause erratic operation of the drive. In a extreme case this can even cause the drive to trip off.
d. The preventive maintenance procedure would involve first turning off power to the drive and waiting until the
DC bus capacitors have discharged to a safe level. Then all of the accessible connections should be inspection
for corrosion and checked for tightness. It should not be necessary to disassemble the drive to perform this
operation.
e. This should be performed once the drive is installed and at least annually afterward. If the drive is subjected to
vibration or wide temperature variations, it should be checked more frequently.
5. Check cooling fans.
a. Cooling fans are used to remove heat from the drive. Proper operation of the cooling fans helps ensure long
drive life by keeping the drive’s components cool. The cooling system should be inspected at least annually,
more frequently when the drive is exposed to extreme conditions.
b. Inspect the heat sinks, air inlets, and air outlets to ensure that there is an open path for air flow.
c. The cooling fans in many VLT drives will turn themselves off when the drive’s temperature is low enough to not
require forced ventilation. To check for proper fan operation if the fans are not running, remove power from the
drive. When power is reapplied the fans should start and run for a few seconds.
d. Listen for unusual noises from the fans when they are running.
e. The VLT drives use a heat sink temperature sensor to help indicate if there is a problem with the cooling system.
If the drive issues a HEAT SINK OVERTEMP. warning or alarm, check the cooling system carefully.
6. Check bus capacitors for voltage balance and/or physical damage.
a. The large DC bus capacitors in the drives are subject to deterioration over an extended period of time. It
generally takes a significant number of years before any problems occur, although high ambient temperatures
and other factors can accelerate this process.
b. Problems with the DC bus capacitors generally first show up as a large “AC ripple voltage” being superimposed
on the DC bus. The VLT 6000 continually monitors for excessive DC bus ripple, so it will generally provide an
early warning of bus capacitor problems. If the drive gives a MAINS PHASE LOSS warning or alarm and a check
of the input AC power line shows it to be balanced under loaded conditions, the DC bus capacitors should be
checked carefully.
c. On drives with an input power line voltage of 380 V AC or larger, the DC bus capacitors are connected as two
banks that are in series with each other. With power applied to the drive, the voltage across the positive half
should be within 10% of the voltage across the negative half.
d. With power removed from the drive, a physical inspection of the capacitors should not show any deformation of
the cases of the capacitors or liquid leaking from them.
e. Low voltage capacitor testers are of no use in checking DC bus capacitors. The main concern is to ensure that
the capacitors don’t have excessive leakage current when the DC bus voltage is applied to it. This cannot be
tested at a low voltage.
f. If one capacitor on the DC bus is found to be weak or damaged, it is important to replace the entire capacitor
bank. A capacitor with an excessive amount of leakage current places excessive stress on other capacitors in
the bank.
g. If it is convenient to access the two halves of the DC bus capacitors, the inspection technique given in “c” and “d”
can be performed annually. Otherwise, it is best to simply let the drive’s internal monitoring circuitry described in
“b” provide an indication of possible problems.
