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6.3.1 No Display Test
An adjustable frequency drive with no display can be the result of several causes. Verify first that
there is no display whatsoever. A single character in the display or a dot in the upper corner of
the display indicates a communication error and is typically caused by an option card not being
properly installed. When this condition occurs, the green power-on LED is illuminated.
If the LCD display is completely dark and the green power-on LED is not lit, proceed with the
following tests.
First test for proper input voltage.
6.3.2 Input Voltage Test
1.
Apply power to the adjustable frequency drive.
2.
Use the DVM to measure the input AC line voltage between the adjustable frequency
drive input terminals in sequence:
L1 to L2
L1 to L3
L2 to L3
For 380–500 V adjustable frequency drives, all measurements must be within the range of 342–
550 VAC. Readings of less than 342 VAC indicate problems with the input AC line voltage. For
525–690 V adjustable frequency drives, all measurements must be within the range of 446–759
VAC. Readings of less than 446 VAC indicate problems with the input AC line voltage.
In addition to the actual voltage reading, the balance of the voltage between the phases is also
important. The adjustable frequency drive can operate within specifications as long as the phase
imbalance is not more than 3%.
Danfoss calculates line imbalance per an IEC specification.
Imbalance = 0.67 X (Vmax – Vmin)/Vavg
For example, if three phase readings were taken and the results were 500 VAC, 478.5 VAC, and
478.5 VAC; then 500 VAC is Vmax, 478.5 VAC is Vmin, and 485.7 VAC is Vavg, resulting in an
imbalance of 3%.
Although the adjustable frequency drive can operate at higher line imbalances, the lifetime of
components, such as DC bus capacitors, will be shortened.
High Power Service Manual for VLT
®
FC Series
Adjustable Frequency Drives
6 Test Procedures
MG.90.L1.22 - VLT
®
is a registered Danfoss trademark
6-21
6
Содержание VLT HVAC FC 100
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