4.4 Visual Inspection
The table below lists a variety of conditions that require visual inspection as part of any initial
troubleshooting procedure.
Inspect For
Description
Auxiliary equipment
Look for auxiliary equipment, switches, disconnects, or input fuses/circuit breakers that may
reside on the input power side of adjustable frequency drive or the output side to motor.
Examine the operation and condition of these items for possible causes of operational faults.
Check the function and installation of pressure sensors or encoders, etc. that provide feed-
back to the adjustable frequency drive.
Cable routing
Avoid routing motor wiring, line power wiring, and signal wiring in parallel. If parallel routing
is unavoidable, try to maintain a separation of 6–8 in (150–200 mm) between the cables or
separate them with a grounded conductive partition. Avoid routing cables through free air.
Control wiring
Check for broken or damaged wires and connections. Check the voltage source of the sig-
nals. Though not always necessary depending on the installation conditions, the use of
shielded cable or a twisted pair is recommended. Ensure the shield is terminated correctly.
Refer to the section on grounding shielded cables in Section 2.
Drive cooling
Check the operational status of all cooling fans. Check the door filters on NEMA 12 (IP54)
units. Check for blockage or constrained air passages. Make sure the bottom connector plate
is installed.
Drive display
Warnings, alarms, drive status, fault history and many other important items are available
via the local control panel display on the drive.
Drive interior
The adjustable frequency drive interior must be free of dirt, metal chips, moisture, and
corrosion. Check for burned or damaged power components or carbon deposits resulting
from catastrophic component failure. Check for cracks or breaks in the housings of power
semiconductors, or pieces of broken component housings loose inside the unit.
EMC considerations
Check for proper installation with regard to electromagnetic capability. Refer to the adjust-
able frequency drive instruction manual and Section 5 of this manual for further details.
Environmental conditions
Under specific conditions, these units can be operated within a maximum ambient of
(122
°
F) [50
°
C]. Humidity levels must be less than 95% non-condensing. Check for harmful
airborne contaminates such as sulfur-based compounds.
Grounding
The adjustable frequency drive requires a dedicated ground wire from its chassis to the
building ground. It is also suggested that the motor be grounded to the adjustable frequency
drive chassis as well. The use of a conduit or mounting the adjustable frequency drive onto
a metal surface is not considered a suitable ground. Check for good ground connections that
are tight and free of oxidation.
Input power wiring
Check for loose connections. Check for proper fusing. Check for blown fuses.
Motor
Check the nameplate ratings of the motor. Ensure that the motor ratings coincide with the
adjustable frequency drives. Make sure that the adjustable frequency drive's motor param-
eters (1-20 – 1-25) are set according to the motor ratings.
Output to motor wiring
Check for loose connections. Check for switching components in the output circuit. Check
for faulty contacts in the switch gear.
Programming
Make sure that the adjustable frequency drive parameter settings are correct according to
motor, application, and I/O configuration.
Proper clearance
These adjustable frequency drives require adequate top and bottom clearance to ensure
proper air flow for cooling in accordance with the adjustable frequency drive size. Adjustable
frequency drives with exposed heatsinks out the back of the adjustable frequency drive must
be mounted on a flat solid surface.
Vibration
Although this is a somewhat subjective procedure, look for any unusual amount of vibration
that the adjustable frequency drive may be subjected to. The adjustable frequency drive
should be mounted solidly or the use of shock mounts employed.
Table 4.1: Visual Inspection
High Power Service Manual for VLT
®
FC Series
Adjustable Frequency Drives
4 Troubleshooting
MG.90.L1.22 - VLT
®
is a registered Danfoss trademark
4-3
4
Summary of Contents for VLT HVAC FC 100
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