Service manual
Digital Inputs
With digital inputs displayed, control terminals 18, 19, 27,
and 29 are shown left to right, with a 1 indicating the
presence of a signal.
If the desired signal is not present in the display, the
problem is either in the external control wiring to the
frequency converter or a faulty control card. To determine
the fault location, use a voltmeter to test for voltage at the
control terminals.
Verify that the control voltage power supply is correct as
follows.
1. Use a voltmeter for measuring voltage at control
card terminal 12 and 13 with respect to terminal
20. The meter should read 21-27 V DC.
If the 24 V supply voltage is not present, test the control
card in 6.2.1 Introduction.
If 24 V is present, proceed with checking the individual
inputs as follows.
2. Connect the (-) negative meter lead to reference
terminal 20.
3. Connect the (+) positive meter lead to the
terminals in sequence.
The presence of a signal at the desired terminal must
correspond to the digital input display readout. A reading
of 24 V DC indicates the presence of a signal. A reading of
0 V DC indicates no signal is present.
Analog Inputs
The value of signals on analog input terminals 53 and 54
can also be displayed. The voltage or current in mA,
depending on the switch setting, is shown in line 2 of the
display.
If the desired signal is not present in the display, the
problem is either in the external control wiring to the
frequency converter, or a faulty control card. To determine
the fault location, use a voltmeter to test for a signal at
the control terminals.
Verify that the reference voltage power supply is correct
as follows.
1. Use a voltmeter for measuring the voltage at
control card terminal 50 with respect to terminal
55. The meter must read between 9.2 and 11.2 V
DC.
If the 10 V supply voltage is not present, conduct
6.4.3 Basic Control Card Voltage Test earlier in this section.
If 10 V is present, proceed with checking the individual
inputs as follows.
2. Connect the (-) negative meter lead to reference
terminal 55.
3. Connect the (+) positive meter lead to desired
terminal 53 or 54.
For analog input terminals 53 and 54, a DC voltage
between 0 and +10 V DC must be read to match the
analog signal sent to the frequency converter. Or a reading
of 0.9 to 4.8 V DC corresponds to a 4-20 mA signal.
NOTE
A (-) minus sign preceding any reading above indicates a
reversed polarity. In this case, reverse the wiring to the
analog terminals.
6.5 Initial Start Up Or After Repair Drive
Tests
Following any repair to a frequency converter or testing of
a frequency converter suspected of being faulty, the
following procedure must be followed. Following this
procedure will ensure that all circuitry in the frequency
converter is functioning properly before putting it into
operation.
1. Perform visual inspection procedures as described
in Table 4.1.
2. Perform static test procedures to ensure that the
frequency converter is safe to start.
3. Disconnect motor cables from output terminals
(U, V, W) of the frequency converter.
4. Apply AC power to frequency converter.
5. Give the frequency converter a run command
and slowly increase reference (speed command)
to approximately 40 Hz.
6. Using an analog volt meter or a DVM capable of
measuring true RMS, measure phase-to-phase
output voltage on all three phases: U to V, U to
W, V to W. All voltages must be balanced within
8 V. If measuring unbalanced voltage, refer to
6.4.2 Input Voltage Test.
7. Stop the frequency converter and remove input
power. Allow 20 minutes for DC capacitors to
fully discharge.
8. Reconnect motor cables to frequency converter
output terminals (U, V, W).
9. Reapply power and restart frequency converter.
Adjust motor speed to a nominal level.
10. Using a clamp-on style ammeter, measure output
current on each output phase. All currents must
be balanced.
Test Procedures
VLT
®
HVAC Basic Drive Service Manual
56 MG90X202 - VLT
®
is a registered Danfoss trademark
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