IGBT gate signal measured with the signal test board: 2 V
per division vertical scale, 50 ms per division time scale.
Unit running at 30 Hz.
4. Using a voltmeter, again check these same signal
board terminals. A correct reading is 2.2–2.5 V
DC.
An incorrect reading of a gate signal indicates that the
control card is defective. Replace the control card.
If the signal is good on the signal test card, but missing on
the gate drive card, the failure can be due to:
•
The gate drive card.
•
The power card.
•
The ribbon cable between them.
Replace the gate drive board and repeat the test.
8.5.12 Current Sensors Test
The current sensors are Hall eîš‚ect devices that send a
signal proportional to the actual output current waveform
to the power card. The current scaling card scales the
signals from the current sensors to the proper level for
monitoring and processing motor control data. A defective
current sensor can cause erroneous ground faults and
overcurrent trips. In these instances, the faults occur only
at higher loads. If the incorrect current scaling card is
installed, the current signals are not scaled properly.
Incorrect scaling could cause erroneous overcurrent trips. If
the current scaling card is not installed, the drive trips.
In D1h–D8h and E1h–E4h units, the current scaling card is
found on the power card. In parallel drive systems, the
current scaling card is found on the MDCIC card on the
control shelf.
To determine the status of the sensors, use the following
tests.
If the control card parameters are set to provide holding
torque at 0 speed, the current shown is greater than
expected. To perform the sensor tests, disable these
parameters.
1. Apply power to the drive.
2. Ensure that the following parameter settings are
disabled:
•
Motor check
•
Premagnetizing
•
DC hold
•
DC brake
•
Any others that create a holding torque
while at 0 speed.
3. Run the drive with a 0 speed reference and check
the output current reading in the display. A
correct reading is approximately 1–2 A. If these
parameters are not disabled, the current shown
exceeds 1–2 A.
If the current is greater than 1–2 A and no current-
producing parameters are active, run the following test:
1. Remove power from the drive.
2. Remove the output motor cables from terminals
U, V, and W.
3. Apply power to the drive.
4. Run the drive with a 0 speed reference, and
check the output current reading in the display. A
correct reading is less than 1 A.
If these tests result in incorrect readings, perform the
following test of the current feedback signals using the
signal test board:
1. Remove power to the drive. Make sure that the
DC bus is fully discharged.
2. Connect the signal test board to power card
connector MK104.
3. Using an ohmmeter, measure the resistance
between terminals 1 and 4, 2 and 4, and 3 and 4
of the signal test board. The correct resistance is
an identical reading on all 3 terminals.
4. Reapply power to the drive.
5. Using a voltmeter, connect the negative (-) meter
lead to terminal 4 (common) of the signal test
board.
6. Run the drive with a 0 speed reference.
7. Measure the AC voltage in sequence at terminals
1, 2, and 3 of the signal test board. These
terminals correspond with current sensor outputs
U, V, and W, respectively. Expect a reading near 0
V, and no greater than 15 mV.
The current sensor feedback signal in the circuit reads
approximately 400 mV at a drive load of 100%. When the
drive is at 0 speed, any reading above 15 mV negatively
impacts the way the drive interprets the feedback signal.
Test Procedures
VLT
®
FC Series, D1h–D8h, Da2/Db2/Da4/Db4, E1h–E4h, J8/J9
114 Danfoss A/S © 02/2019 All rights reserved. MG94A502
88
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