No Display Test; Input Voltage Test; Basic Control Card Voltage Test - Danfoss VLT Series Service Manual

5.2.1 No Display Test

A 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 properly installed. Under this
condition 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.

5.2.1.1 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
For 380 - 480 V drives, all measurements must be within the
range of 342 to 528 VAC (or 342 to 550 VAC for VLT 5000).
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 range of 446 to 759 VAC (or 446 to 660
VAC for VLT 6000). 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.
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 drive can operate at higher line imbalances, the
lifetime of components, such as DC bus capacitors, will be
shortened.
5-14
VLT is a registered Danfoss trademark
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
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. Prior to replacing fuses or resetting
breakers, perform static tests described in
section 5.1.
If the Input Voltage Test was successful check for voltage to
the control card.

5.2.1.2 Basic Control Card Voltage Test

1. Use voltmeter to measure 24 VDC control
voltage at terminal 12 with respect to terminal
20. Meter should read between 21 and 27 VDC.
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. If still unsuccessful proceed to the Switch Mode
Power Supply (SMPS) test.
2. Measure 10 V DC control voltage at terminal 50
with respect to terminal 55. Meter should read
between 9.2 and 11.2 VDC.
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
than continue. Remember to check out the customer
connections. If still unsuccessful proceed to the SMPS test.
A correct reading of both control card voltages would indicate
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 procedures
in Section 6 or 7.