Service manual
4.4 Visual Inspection
Visually inspect the conditions in Table 4.1 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
input power side of frequency converter or output side to motor. Examine operation and condition of
these items as possible causes for operational faults. Check function and installation of pressure sensors
or encoders (etc.) used for feedback to frequency converter.
Cable routing Avoid routing motor wiring, AC line wiring, and signal wiring in parallel. If parallel routing is
unavoidable, try to maintain a separation of 150–200 mm (6-8 inches) 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 signals. 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.
Frequency converter cooling Check operational status of all cooling fans. Check door filters on NEMA 12 (IP54) units. Check for
blockage or constrained air passages. Verify bottom gland plate is installed.
Frequency converter display Warnings, alarms, frequency converter status, fault history and many other important items are available
through the display on the local control panel of frequency converter.
Frequency converter interior Frequency converter interior must be free of dirt, metal chips, moisture, and corrosion. Check for burnt
or damaged power components or carbon deposits that were the result of a 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 frequency converter
instruction manual and this chapter for further details.
Environmental conditions
Under specific conditions these units can be operated within a maximum ambient of 50
°
C (122
°
F).
Humidity levels must be less than 95% non-condensing. Check for harmful airborne contaminates such
as sulfur based compounds.
Grounding The frequency converter requires a dedicated ground wire from its chassis to the building ground. It is
also suggested that the motor be grounded to the frequency converter chassis as well. The use of
conduit or mounting of the frequency converter to 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 nameplate ratings of motor. Ensure that motor ratings coincide with frequency converters. Ensure
frequency converter's motor parameters (1–20 to 1–25) are set according to motor ratings.
Output to motor wiring Check for loose connections. Check for switching components in output circuit. Check for faulty contacts
in switch gear.
Programming Ensure frequency converter parameter settings are correct according to motor, application, and I/O
configuration.
Proper clearance These frequency converters require top and bottom clearance adequate to ensure proper air flow for
cooling in accordance with the frequency converter size. frequency converters with exposed heat sinks
out the back of the frequency converter must be mounted on a flat solid surface.
Vibration Though somewhat subjective look for an unusual amount of vibration that the frequency converter may
be subjected to. The frequency converter should be mounted solidly or the use of shock mounts
employed.
Table 4.1 Visual Inspection
Troubleshooting
VLT
®
HVAC Basic Drive Service Manual
32 MG90X202 - VLT
®
is a registered Danfoss trademark
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