8.5.1 No Display Test
A drive with no display can be the result of several causes.
Verify rst that there is no display.
If the display is dark and the green power LED is not lit,
proceed with the following tests.
8.5.2 Input Voltage Test
If the drive is equipped with optional equipment, ensure
that it is functioning properly. See chapter 8.4.7 Mains
Fuse/DC Fuse Test, chapter 8.4.8 Disconnect Test,
chapter 8.4.9 Circuit Breaker Test, and
chapter 8.4.10 Contactor Test.
Input voltage test
1. Apply power to the drive.
2. Use the voltmeter to measure the input mains
voltage between the drive input terminals in
sequence:
L1 to L2
L1 to L3
L2 to L3
For 380–480 V/380–500 V 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 mains
voltage. For 525–690 V 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 mains voltage.
In addition to the actual voltage reading, the balance of
the voltage between the phases is also important. The
drive can operate within specications as long as the
imbalance of supply voltage is not more than 3%.
Danfoss calculates mains imbalance per an IEC speci-
cation.
•
Imbalance = 0.67 X (V
max
– V
min
)/V
avg
For example, if 3-phase readings are taken and the results
are 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 drive can operate at higher mains
imbalances, this condition can 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
TEST ORDER
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 8.4 Static Test Procedures.
If the input voltage test was successful, check for voltage
to the control card.
8.5.3 Basic Control Card Voltage Test
1. Measure the control voltage at terminal 12 in
relation to terminal 20. A correct reading is 24 V
DC (21–27 V DC).
An incorrect reading can indicate that a fault in the
customer connections is loading down the supply. Check
the customer connections. Unplug the terminal strip and
repeat the test.
2. Measure the 10 V DC control voltage at terminal
50 in relation to terminal 55. A correct reading is
10 V DC (9.2–11.2 V DC).
An incorrect reading can indicate that a fault in the
customer connections is loading down the supply. Check
the customer connections. Unplug the terminal strip and
repeat the test. A correct reading of both control card
voltages indicates that the LCP or the control card is
defective. Replace the LCP. If the problem persists, replace
the control card.
8.5.4 DC Bus Voltage Test
DC bus voltage test part I
1. Using a voltmeter, read the DC bus voltage.
2.
In VLT
®
Parallel Drive Modules, check the voltage
at the DC fuse terminals. See chapter 8.4.7 Mains
Fuse/DC Fuse Test for DC bus location.
Check that the measured voltage is at least 1.35 x the AC
input voltage.
Test Procedures Service Guide
MG94A502 Danfoss A/S © 02/2019 All rights reserved. 107
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