Gate Resistor Test; Mains Fuse/Dc Fuse Test; Disconnect Test - Danfoss VLT FC Series Service Manual

Test Procedures
The relationship between temperature and resistance is
nonlinear. At 25 °C (77 °F), the resistance is approximately
5k Ω. At 0 °C (32 °F), the resistance is approximately 13.7
k Ω. At 60 °C (140 °F), the resistance is approximately 1.5
k Ω. The higher the temperature, the lower the resistance.

8.4.6 Gate Resistor Test

Mounted to each IGBT module is an IGBT gate resistor card
containing gate resistors for the IGBT transistors.
Occasionally, a defective IGBT can produce correct readings
in the previous tests. Typically, an IGBT failure results in the
failure of the gate resistors, so the gate resistor test can
identify an IGBT failure.
NOTICE
DRIVE TYPE
This test is applicable to only D-sized drives. E1h–E4h
drives do not have test connectors on the gate drive
card.
To access the gate drive card, see chapter 10.2.17 Gate
Drive Card, chapter 11.2.14 Gate Drive Card, or
chapter 13.2.14 Gate Drive Card.
In D-sized drives, a 3-pin test connector is found on the
gate drive card near each gate signal lead. These leads are
labeled:
•
MK500
•
MK502
•
MK600
•
MK602
•
MK700
•
MK702
•
MK200 (if brake option is present).
See Illustration 8.8.
For clarification, refer to the 3 pins as 1, 2, and 3, reading
bottom to top. Pins 1 and 2 of each connector are in
parallel with the gate drive signal sent to the IGBTs. Pin 1
is the signal and pin 2 is common.
Gate resistor test
1. With an ohmmeter, measure pins 1 and 2 of each
test connector.
2. Confirm that the reading is the same for each test
connector.
Incorrect reading
An incorrect reading can indicate that:
•
The gate signal wires are not connected from the
gate drive card to the gate resistor board.
•
The gate resistors are defective.
MG94A502
Service Guide
Connect the gate signal wires if necessary. If any of the
resistors are defective, replace the entire IGBT module
assembly. See chapter 10.2.19 IGBTs, chapter 11.2.19 IGBTs,
or chapter 13.2.22 IGBTs.

8.4.7 Mains Fuse/DC Fuse Test

In D1h–D8h units, optional mains fuses are located in
either of 2 places. Usually, they are found in the main
enclosure. When an optional contactor and disconnect are
both present, the mains fuses are located in the extended
options cabinet between these 2 components. In E1h–E4h
units, the optional AC fuses are located in the main
enclosure mounted in front of the input plate.
In parallel drive modules, the mains fuses are located in
the main module enclosure. In parallel drive systems, the
DC fuses are found at the top of each module.
Mains fuse/DC fuse test
Perform the following fuse test. If the unit is a parallel
drive module, perform the test on the DC fuse.
1.
2.
A short circuit indicates good continuity.
Incorrect reading
An open circuit means that the fuse requires replacement.
Perform the additional static checks before replacing the
fuse.

8.4.8 Disconnect Test

The mains disconnect switch is optional. In D-sized drives,
the disconnect is located in the extended options cabinet.
In E-sized drives, the disconnect option is integrated into
the drive enclosure.
For the mains disconnect test:
1.
2.
3.
An open circuit (infinite resistance) is a correct reading. A
short circuit (0 Ω) indicates a problem with the switch.
1.
2.
A short circuit (0 Ω) is a correct reading. An open circuit
(infinite resistance) or high-resistance reading indicates a
problem with the switch. Replace the disconnect switch.
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Use an ohmmeter set to measure the ohms.
Measure the resistance across each fuse.
Use an ohmmeter set to read ohms.
Open the disconnect switch.
Measure the resistance across each of the 3
phases.
Close the disconnect switch.
Measure the resistance across each of the 3
phases.
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