Siemens S120 driver trips as soon as it is powered on

Siemens S120 driver trips as soon as it is powered onTemperature fault, grounding fault, power component fault, fuse burning, tripping, machine explosion, under voltage, over-current, no DC600V DC output, yellow light not on, indicator lights not on, red light on, unable to move load, circuit board burned out, output given command not working, display alarm preparation not clear, servo drive fault, encoder alarm, DP communication fault, X-axis fault, Y-axis not working, Z-axis not enabled, system reports 3805003002131885300207930, f07016, 702844 repairSiemens S120 driver trips as soon as it is powered onUsually, it is a fault that triggers protection upon power on. Based on recent (January March 2026) maintenance data, the main causes and troubleshooting steps are as follows:

Common reasons

Abnormal power connection: unstable input voltage, phase loss, loose wiring or poor contact

Internal short circuit or ground fault: power module IGBT、 There is a short circuit/grounding on the DC bus or motor side

Overload or overcurrent: Excessive load, motor jamming, or improper parameter settings result in excessive starting current

Hardware damage: aging or breakdown of power modules, control boards (such as CU310), current detection circuits, capacitors, and other components

Pre charging failure: The S120 power module needs to complete the pre charging process after power on. If this process is abnormal (such as damaged pre charging resistors or contactor faults), it will trigger a trip

Systematic troubleshooting steps

Power off and check external wiring

Confirm the stability of the 380V input power supply (allowable range: 380V ± 10%)

Check all power lines, motor lines, and encoder lines for looseness, burning, or short circuits.

Disconnect load test

Disconnect the motor from the driver and power on S120 separately.

If the trip still occurs → the fault is inside the driver;

If it does not trip, the problem may lie in the motor or mechanical load

Observe the indicator lights and fault codes

Is the RDY light always on red? Are there any other alarms (such as F30021, F07900, etc.)

If there is a display screen, record the specific fault code and refer to the S120 System Manual.

Inspect key internal components

Measure whether the DC bus voltage is normal (normal should reach 570V -600V)

Check if the pre charging circuit, main contactor, and auxiliary contacts are working properly

Use a multimeter to check if the power module (IGBT) is short circuited

Environmental and maintenance factors

Is the environment damp and dusty? Is the cooling fan running? ‌

Long term operation without cleaning may lead to insulation degradation or false triggering of overheating protection.

Suggested handling method

If you have experience in electrical maintenance, you can follow the above steps to troubleshoot on your own.

If you do not have professional tools or experience, it is recommended to contact a professional maintenance organization. As S120 belongs to high-precision industrial drives, self disassembly and repair can easily cause secondary damage.