Service manual

Dynamic tests are performed without the motor being
connected to UVW connector. Program the frequency
converter to approximately 50 Hz on start.
Dynamic tests can indicate if one of the IGBT does not
switch, and the output voltage drops on the fault terminal,
UVW.
Dynamic tests are conducted to check the IGBT. Conduct
the test without the motor being connected to the
frequency converter. Program the multimeter to AC 1000
V.
Described next is the procedure to conduct the dynamic
test on the IGBT.
1. Connect the positive terminal of the multimeter
lead to the U connector, and connect the
negative terminal to the V terminal.
2. Connect the positive terminal of the multimeter
lead to the U connector, and connect the
negative terminal to the W terminal.
3. Connect the positive terminal of the multimeter
lead to the V connector, and connect the
negative terminal to the W terminal.
The meter reading is 450 V ±25 V when performing the
dynamic test at 400 V mains, and 50 Hz/1500 RPM output
depending on the instrument used.
The reading must be within ±1.5%.
6.4.1
No Display Test (Display is Optional)
A frequency converter with no display in the LCP can be
the result of several causes. First, verify that there is no
display. A single character in the display or a dot in the
upper corner of the display indicates a communication
error. Check that all option cards are properly installed.
When this condition occurs, the green power-on LED is
illuminated.
If the LCD display is dark and the green power-on LED is
not lit, proceed with the following tests.
First test for proper input voltage.
6.4.2
Input Voltage Test
1. Apply power to frequency converter.
2. Use the DVM to measure the input mains voltage
between the frequency converter input terminals
in sequence:
L1 to L2
L1 to L3
L2 to L3
For 380 V frequency converters, 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 525–600 V frequency converters, all measurements
must be within the range of 446–600 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
frequency converter can operate within specifications as
long as the imbalance of supply voltage is not more than
3%.
Danfoss calculates mains imbalance per an IEC specifi-
cation.
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 frequency converter can operate at higher
mains imbalances, the lifetime of components, such as DC
bus capacitors, is shortened.
Incorrect reading
CAUTION
Open (blown) input fuses or tripped circuit breakers
usually indicate a more serious problem. Before replacing
fuses or resetting breakers, perform static tests.
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
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 with
respect to terminal 20. The meter must read
21-27 V DC.
An incorrect reading here could indicate that a fault in the
customer connections loads down the supply. Disconnect
Test Procedures
VLT
®
HVAC Basic Drive Service Manual
MG90X202 - VLT
®
is a registered Danfoss trademark 53
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