Overcurrent or Short Circuit
Overcurrent protection engages when load current exceeds the programmed threshold, typically 105-115% of rated output capacity, for longer than the programmed delay time (usually 10-50ms). This fault can indicate either a genuine overload condition or failure of current sensing circuitry causing false triggering.
Error Code
AL69
Severity
Critical
Equipment
Power Supply
Manufacturer
Danfoss
Yellow overcurrent LED illuminated with output voltage present but reduced to 80-90% of rating
Output current limiting at exactly 115% of nameplate rating regardless of load demand
Periodic shutdown and restart cycles every 5-10 seconds under moderate load conditions
Main switching frequency audibly shifts from normal 50-100kHz to lower 20-30kHz range
Output voltage ripple increases to 200-500mV peak-to-peak compared to normal 50mV specification
Temperature of output rectifiers and filter inductors rises 15-20°C above normal operating levels
Aging output filter inductors with increased DCR causing higher voltage drop and apparent overcurrent
Current transformer or Hall effect sensor drift resulting in 10-15% calibration error
Control IC analog reference voltage drift affecting overcurrent threshold by 5-10%
High ambient temperature causing component parameter shifts in current sensing circuit
Load equipment with high inrush current exceeding brief overcurrent immunity of 150% for 1ms
Main transformer core approaching saturation due to DC bias from asymmetrical switching
De-energize system using LOTO procedures and allow 15-minute cooling period before component access
Measure output inductor DCR with milliohm meter - should be within 10% of design specification
Calibrate current sensing using precision DC current source at 90% and 110% of rated output
Check control IC reference voltage with precision DVM - should be within 1% of specified value (typically 2.5V or 5V)
Verify proper cooling airflow and clean heat sinks - ambient at current sensors should not exceed 60°C
Replace main transformer if core loss measurements show >15% increase from original specification
Perform dynamic load test with programmable electronic load ramping from 0-120% in 10% steps while monitoring current limit activation point
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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