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Test Procedures
6.3.2 Warnings
WARNING
Never disconnect the input cabling to the frequency
converter with power applied due to danger of severe
injury or death.
WARNING
Take all the necessary safety precautions for system start
up prior to applying power to the frequency converter.
WARNING
For dynamic test procedures, main input power is required
and all devices and power supplies connected to mains are
energized at rated voltage. Use extreme caution when
conducting tests in a powered frequency converter.
Contact with powered components could result in
electrical shock and personal injury.
NOTE
Test procedures in this section are numbered for reference
only. Tests do not need to be performed in this order.
Perform tests only as necessary.
6.3.3 No Display Text
A frequency converter with no display can be the result of
several causes.
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.
6.3.4 Input Voltage Test
1.
Apply power to drive.
2.
Use DVM to measure input line voltage between
drive input terminals in turn:
L1 to L2
L1 to L3
L2 to L3
NOTE: With 12-pulse units, measure input line
voltage between drive input terminals:
L11/L12
L21/L22L3
L31/L32
For 380 - 480 V drives, all measurements must be within
the range of 342 to 528 VAC. Readings of less than 342
VAC indicate problems with the input AC line voltage. For
525 - 690 V drives, all measurements must be within the
High Power Service Manual for Modular F Frame Drives
range of 446 to 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
drive can operate within specifications as long as the
phase imbalance is not more than 3%.
Danfoss calculates line imbalance per an IEC specification.
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 drive can operate at higher line imbalances,
the lifetime of components, such as DC bus capacitors, will
be shortened.
Incorrect reading
An incorrect reading here requires that the main supply be
investigated further. Typical items to check would be:
Open (blown) input fuses or tripped circuit breakers
usually indicate a more serious problem. Prior to replacing
fuses or resetting breakers, perform static tests.
If the Input Voltage Test was successful check for voltage
to the control card.
6.3.5 Basic Control Card Voltage Test
If an external 24 VDC supply is used for control voltage, it
would be likely for switch 4 on the control card to be
open. This opens the common connection to terminal 20.
If this is the case, measure terminal 12 with respect to
terminal 39.
An incorrect reading here could indicate the supply is
being loaded down by a fault in the customer connections.
Unplug the terminal strip and repeat the test. If this test is
successful then continue. Remember to check out the
customer connections.
®
MG90K202 - VLT
is a registered Danfoss trademark
Imbalance = 0.67 X (Vmax – Vmin) / Vavg
Open (blown) input fuses or tripped circuit
breakers
Open disconnects or line side contactors
Problems with the power distribution system
CAUTION
1. If the Input Voltage Test was successful check
for voltage to the control card.
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