DC Link Overvoltage
The DC link capacitor bank voltage has exceeded safe operating limits, typically above 450VDC, indicating failure of voltage regulation circuits. This fault directly threatens connected equipment and requires immediate shutdown to prevent catastrophic component damage.
Error Code
E7925
Severity
Critical
Equipment
Power Supply
Manufacturer
Bosch Rexroth
Red overvoltage fault LED solid with accompanying audible alarm beeper at 1kHz
DC link voltage reads 465-520VDC measured across main filter capacitors C1/C2
All connected drives and controllers in emergency stop mode with F0010 overvoltage codes
Visible arcing or corona discharge at high voltage connection points under low light
Main contactor K1 chattering due to coil voltage exceeding 110% of rating
Power supply case temperature elevated to 75-80°C when normal operating range is 45-55°C
Shorted brake chopper IGBT Q5 allowing uncontrolled voltage buildup across DC link
Failed overvoltage protection circuit with damaged voltage comparator IC LM311
Defective main switching transformer T1 with turn ratio shifted from 3:1 to 2.5:1
Open brake resistor R20 preventing energy dissipation during regenerative conditions
Lightning surge damage to MOV surge suppressors MOV1-MOV3 in input protection circuit
Failed DC link capacitor C1 with internal short causing resonant voltage doubling effect
Immediately implement emergency lockout/tagout and evacuate personnel from 10-foot radius around equipment
Allow 30-minute cooldown period before approaching equipment wearing appropriate PPE including face shield
Use insulated hot stick to discharge DC link through 5kΩ 100W ceramic resistor bank
Measure brake chopper IGBT Q5 collector-emitter voltage with high voltage differential probe
Test overvoltage comparator circuit reference voltage - should be 4.50V ±1% at pin 3 of LM311
Replace failed brake chopper IGBT, gate driver board, and overvoltage protection components per service manual
Perform comprehensive system checkout with oscilloscope monitoring transient response during simulated fault conditions
Safety First: Always isolate power and follow LOTO (Lockout/Tagout) procedures before working on electrical components. If unsure, contact a certified repair technician.
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