6.4.1 No Display Test
An adjustable frequency drive with no display can be the
result of several causes. Verify first that there is no display.
If the LCD display is dark and the green power-on LED is
not lit, proceed with the following tests.
6.4.2 Input Voltage Test
If the adjustable frequency drive is equipped with optional
equipment, ensure that it is functioning properly. See
,
, and
for more information.
1.
Apply power to the adjustable frequency drive.
2.
Use the voltmeter 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 380–480 V/380–500 V adjustable frequency drives, all
measurements must be within the range of 342–550 V AC.
Readings of less than 342 V AC 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 V AC. Readings of less than 446 V AC 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 specifi-
cations as long as the supply voltage imbalance is not
more than 3%.
Danfoss calculates line imbalance per an IEC specification.
Imbalance = 0.67 X (V
max
– V
min
)/V
avg
For example, if three-phase readings were taken and the
results were 500 V AC, 478.5 V AC, and 478.5 V AC; then
500 V AC is V
max
, 478.5 V AC is V
min
, and 485.7 V AC is V
avg
,
resulting in an imbalance of 3%.
Although the adjustable frequency drive can operate at
higher line imbalances, this will shorten the lifetime of
some components, such as DC bus capacitors.
Incorrect reading
An incorrect reading here requires further investigation of
the main supply. Typical items to check would be:
Open (blown) input fuses or tripped circuit
breakers
Open disconnects or line side contactors
Problems with the power distribution system
CAUTION
Open (blown) input fuses or tripped circuit breakers
usually indicate a more serious problem. Before
replacing fuses or resetting breakers, perform static tests
described in
chapter 6.3 Static Test Procedures
If the input voltage test was successful, check for voltage
to the control card.
6.4.3 Basic Control Card Voltage Test
1. Measure the control voltage at terminal 12
regarding terminal 20. A correct reading is 24 V
DC (21–27 V DC).
An incorrect reading here could indicate that a fault in the
customer connections is loading down the supply. Unplug
the terminal strip and repeat the test. If this test is
successful, continue. Remember to check the customer
connections.
2. Measure the 10 V DC control voltage at
terminal 50 regarding terminal 55. A correct
reading is 10 V DC (9.2–11.2 V DC).
An incorrect reading here could indicate that a fault in the
customer connections is loading down the supply. Unplug
the terminal strip and repeat the test. If this test is
successful, continue. Remember to check the customer
connections.
A correct reading of both control card voltages would
indicate that the LCP or the control card is defective.
Replace the LCP with a known good one. If the problem
persists, replace the control card in accordance with the
disassembly instructions.
Test Procedures
Service Manual
MG94A222
Danfoss A/S © Rev. 2014-02-10 All rights reserved.
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