Fault tracing vacon • 153
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9
9.3 DC link test (without motor)
NOTE! There will be dangerous voltages present during this test!
1. Read carefully the safety instructions in Chapter 1 and follow them.
2. Connect a variable DC power supply to DC+ and DC– terminals. Make sure that all
polarities are correct.
3. Slowly charge up the DC link to nominal voltage. Allow the system to remain at this level
for at least one minute and check current.
4. If possible, continue increasing the DC link voltage up to the trip limit. Fault F2 (see
Chapter 9) should occur at 911 VDC (NX_5, 400…500-volt units), at 1200 VDC (NX_6,
525…690-volt units) and 1300 VDC (NX_8, 525...690-volt units). Do not increase the
voltage over the trip limit.
5. Bring the power supply voltage back to zero. Allow sufficient time for the capacitors to
discharge.
6. Check the DC bus voltage with a multimeter. When you read zero volts disconnect the
power supply and reconnect all wires to the phase module.
7. If the phase module has been de-energized for an extended period of time (six months or
longer) allow this voltage to remain for a minimum of 30 minutes – even 4 hours if time
permits.
Through the above test procedure, two things are achieved: 1) It allows the caps to partially reform
due to storage and shipping; 2) It allows any device failures to evidence themselves with a low power
failure.
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