The FANUC SV0442 alarm indicates a DC link charging abnormal condition in the inverter. This alarm occurs when the common power supply detects an abnormal condition in the DC link backup discharge circuit or when the drive cannot charge the main circuit within the specified time after emergency stop is released.
In a FANUC servo system, the DC link circuit must be charged correctly after the machine power sequence is enabled. If the main power is not supplied in time, the voltage is insufficient, the phase sequence is incorrect, the MCC contactor does not work properly, or a connected servo/spindle drive causes a DC bus short circuit, the CNC system may generate the SV0442 alarm.
This alarm is usually related to the power supply module, also called the PSM. When SV0442 occurs, all axes may show servo alarms, and it may also appear together with a spindle alarm such as SP9033. In the electrical cabinet, the power supply module LED may display alarm code 5.
Quick Summary of FANUC SV0442 Alarm
| Alarm Code | SV0442 |
|---|---|
| Alarm Meaning | DC Link Charging Abnormal in Inverter |
| Main Cause | The DC link charging circuit or backup discharge circuit is abnormal. |
| Related Unit | Common power supply / PSM power supply module |
| PSM LED Display | Alarm 5 |
| Related Alarm | SP9033 may occur together with SV0442 |
| Key Check Items | Main power voltage, emergency stop release sequence, MCC contactor, CX48 phase sequence, DC bus short circuit, spindle drive, servo drive, power supply module capacity |
What Does FANUC SV0442 Alarm Mean?
SV0442: DC Link Charging Abnormal in Inverter
The FANUC SV0442 alarm means that the drive DC link charging circuit has detected an abnormal condition. After emergency stop is released, the drive does not charge the main circuit within the specified time.
The DC link is the DC bus section of the drive system. It is supplied by the power supply module and shared by the connected servo and spindle drive modules. If the DC link cannot be charged correctly, the system will detect an abnormal charging condition and issue SV0442.
This alarm commonly occurs on the power supply module side. When it occurs, the PSM LED may show alarm 5. The machine may show alarms on all axes, and a spindle alarm such as SP9033 may also appear at the same time.
Common Causes of FANUC SV0442 Alarm
The most common causes of FANUC SV0442 DC link charging abnormal alarm include:
1. Main Power Is Not Supplied Immediately After Emergency Stop Release
After emergency stop is released, strong power must be supplied to the amplifier immediately, and the voltage must be sufficient.
If the main circuit power is delayed, missing, or not supplied correctly, the DC link may fail to charge within the specified time and SV0442 may occur.
2. Main Power Voltage Is Insufficient
If the input voltage to the power supply module is too low, the DC link charging process may fail.
For a normal 200V-class system, the main power is usually around 220V. For a high-voltage module, the main power is usually around 380V. The actual voltage should be measured and confirmed according to the machine and module specification.
3. Missing Phase in the Main Power Supply
If the main power supply has a missing phase, the power supply module may not be able to charge the DC link correctly.
Check whether the three-phase input power is normal and whether there is any phase loss in the main power circuit.
4. MCC Contactor Does Not Pull In Correctly
The MCC contactor in the main power circuit must operate normally.
If the MCC does not pull in, if the contactor contacts are poor, or if the MCC control circuit is abnormal, the main power may not be supplied correctly to the power supply module.
5. CX48 Phase Sequence Does Not Match the Main Power
If the power supply module has a CX48 connector, the power connected to CX48 must have the same phase sequence as the main power.
If the CX48 phase sequence is different from the amplifier main power phase sequence, SV0442 may occur. Confirm that the CX48 connector power phase sequence is consistent with the main circuit power phase sequence.
6. DC Bus Short Circuit in a Connected Drive Module
A connected spindle drive or servo drive may cause a DC bus short circuit.
If a drive module connected behind the power supply module has a DC bus short circuit, the power supply module may fail to charge the DC link properly and generate SV0442.
7. Faulty Servo Drive or Spindle Drive
If the DC bus side of a connected servo or spindle drive is abnormal, SV0442 may occur.
In this case, the faulty servo drive or spindle drive should be identified and replaced. Testing can be performed by disconnecting the DC bus shorting bar above the drive module when safe and appropriate.
8. Power Supply Module Failure
If the main power voltage, MCC, CX48 phase sequence, and connected drive modules have all been checked but SV0442 remains, the power supply module may be faulty.
In this case, the PSM power supply module should be replaced.
9. Power Supply Module Capacity Is Insufficient After Adding New Drive Modules
If SV0442 appears only after adding a new drive module, the number or capacity of connected spindle and servo drive modules may exceed the power supply module capacity.
The connected SPM spindle drive modules and SVM servo drive modules should be checked. If the power supply module capacity is insufficient, select a suitable power supply module according to the connected drive capacity.
How to Troubleshoot FANUC SV0442 Alarm
When troubleshooting FANUC SV0442, the first step is to confirm when the alarm occurs and whether the power supply module LED displays alarm 5.
You may need to check:
- Whether the alarm occurs immediately after emergency stop is released
- Whether the alarm occurs during machine operation
- Whether the alarm appeared after adding a new drive module
- Whether the PSM power supply module LED displays alarm 5
- Whether all axes show alarms at the same time
- Whether spindle alarm SP9033 appears together with SV0442
- Whether main power is supplied immediately after emergency stop release
- Whether the main power voltage is sufficient, such as 220V for a 200V-class system or 380V for a high-voltage module
- Whether the main power has a missing phase
- Whether the MCC contactor pulls in normally
- Whether the MCC contacts and control circuit are normal
- Whether the CX48 phase sequence is the same as the main power phase sequence
- Whether the DC bus voltage behind the power supply module is normal
- Whether a connected servo drive or spindle drive has a DC bus short circuit
- Whether disconnecting the DC bus shorting bar helps locate the faulty module
- Whether the power supply module capacity is sufficient for the connected SPM and SVM modules
- Whether the power supply module needs to be replaced
Recommended Solution
The correct solution for FANUC SV0442 depends on whether the alarm is caused by main power supply timing, voltage problem, MCC contactor failure, CX48 phase sequence mismatch, DC bus short circuit, drive module failure, or power supply module capacity shortage.
1. Confirm the Alarm Occurrence Condition
First, confirm the machine condition when the alarm occurs.
Check whether SV0442 occurs immediately after emergency stop is released, during machine operation, or only after adding a new drive module. This helps determine whether the problem is related to main power supply, connected drive modules, or power supply module capacity.
2. Check PSM LED Alarm Display
Open the electrical cabinet and check the power supply module LED display.
When SV0442 occurs, the PSM power supply module may display alarm 5. This indicates that the power supply module side should be checked carefully.
3. Check Main Power Voltage and Phase Loss
Check whether the main power voltage supplied to the power supply module is sufficient and stable.
For a standard 200V-class system, the voltage is usually around 220V. For a high-voltage module, the voltage is usually around 380V. Also check whether the main power has any phase loss.
4. Check MCC Contactor and Main Power Control Circuit
Confirm whether the main circuit MCC contactor pulls in correctly after emergency stop is released.
Check the MCC contactor, contact condition, coil control circuit, and main power control circuit. If the MCC does not work correctly, the DC link may not charge within the specified time.
5. Measure the DC Bus Side of Connected Drive Modules
Measure whether the DC bus side of the connected spindle drives and servo drives is normal.
If there is a DC bus short circuit in a connected drive module, replace the faulty servo drive or spindle drive. The DC bus shorting bar above the drive module may be disconnected for isolation testing when it is safe and appropriate.
6. Check CX48 Phase Sequence
If the power supply module has a CX48 connector, confirm whether the CX48 power phase sequence is the same as the main power phase sequence.
If the phase sequence is inconsistent, correct the wiring. The CX48 power phase sequence must match the main circuit power phase sequence.
7. Check Other Power-Related Wiring
Check whether other power-related wiring is abnormal.
This includes main power cable connection, MCC wiring, control circuit wiring, connector contact, grounding condition, and wiring changes after maintenance or drive replacement.
8. Replace the Power Supply Module If the Alarm Remains
If the above checks do not solve the alarm, replace the power supply module.
A faulty PSM power supply module may fail to charge the DC link properly or may detect an abnormal backup discharge circuit condition.
9. If the Alarm Appears After Adding a New Drive, Check PSM Capacity
If SV0442 appears only after adding a new servo or spindle drive, check whether too many modules are connected to the power supply module.
The total connected capacity of SPM spindle drive modules and SVM servo drive modules may exceed the power supply module capacity. In this case, select a suitable power supply module according to the connected drive capacity.
If your machine shows FANUC SV0442 DC link charging abnormal alarm, please contact REACO CNC directly. Our team can help check PSM alarm 5, main power voltage, MCC contactor, CX48 phase sequence, DC bus short circuit, connected servo/spindle drive modules, and power supply module replacement options.
REACO CNC Support for FANUC SV0442 Alarm
REACO CNC provides support for FANUC CNC systems, PSM power supply modules, servo drives, spindle drives, DC link circuits, MCC contactors, CX48 wiring, and related CNC hardware issues.
We can help with:
- FANUC CNC alarm analysis
- FANUC SV0442 alarm troubleshooting
- DC link charging abnormal issue analysis
- PSM LED alarm 5 checking support
- Main power voltage and phase loss checking guidance
- MCC contactor and control circuit troubleshooting
- CX48 phase sequence checking
- DC bus short circuit isolation guidance
- Servo drive and spindle drive fault analysis
- Power supply module capacity selection support
- Power supply module repair or replacement support
- Replacement FANUC CNC parts supply
If you are not sure whether the SV0442 alarm is caused by emergency stop release timing, insufficient main power voltage, missing phase, MCC contactor failure, CX48 phase sequence error, DC bus short circuit, drive module failure, or insufficient PSM capacity, you can send us the CNC system model, alarm screen, power supply module model, PSM LED display, servo/spindle drive models, wiring photos, and machine power-on condition. Our team will help check the possible cause.
FAQ About FANUC SV0442 Alarm
What is FANUC SV0442 alarm?
FANUC SV0442 alarm means DC link charging abnormal in the inverter. It occurs when the DC link backup discharge circuit is abnormal or when the drive cannot charge the main circuit within the specified time after emergency stop is released.
What causes FANUC SV0442 DC link charging abnormal alarm?
The alarm may be caused by insufficient main power voltage, missing phase, MCC contactor failure, abnormal main power control circuit, CX48 phase sequence mismatch, DC bus short circuit in a connected drive module, faulty servo/spindle drive, power supply module failure, or insufficient power supply module capacity.
What does PSM LED alarm 5 mean?
When SV0442 occurs, the power supply module LED may display alarm 5. This indicates a power supply module-side abnormality related to DC link charging or discharge circuit condition.
Why does SV0442 appear with all-axis alarms?
SV0442 is often related to the common power supply module. Because the DC link is shared by multiple servo and spindle drive modules, a power supply-side charging failure may cause alarms on all axes.
Can SV0442 appear together with SP9033?
Yes. SV0442 may appear together with spindle alarm SP9033 when the power supply module or DC link charging condition is abnormal.
What should I check first when SV0442 occurs?
First, confirm whether the alarm occurs immediately after emergency stop is released, during operation, or after adding a new drive. Then check the PSM LED display, main power voltage, phase loss, MCC contactor, and main power control circuit.
Can CX48 phase sequence cause SV0442?
Yes. If the power supply module has a CX48 connector, the CX48 power phase sequence must match the main power phase sequence. If the phase sequence is different, SV0442 may occur.
Can a servo drive or spindle drive cause SV0442?
Yes. If a connected servo drive or spindle drive has a DC bus short circuit, the power supply module may fail to charge the DC link and generate SV0442.
Why did SV0442 appear after adding a new drive?
If SV0442 appears after adding a new drive, the connected SPM and SVM module capacity may exceed the power supply module capacity. A larger or suitable power supply module may be required.
How can I fix FANUC SV0442 alarm?
Check the alarm timing, PSM LED alarm 5, main power voltage, phase loss, MCC contactor, main power control circuit, CX48 phase sequence, DC bus side of connected drives, DC bus short circuit condition, and PSM capacity. Replace the faulty servo/spindle drive or power supply module if necessary.
Need Help with FANUC SV0442 Alarm?
If your CNC machine has a FANUC SV0442 DC link charging abnormal alarm, please contact REACO CNC. We can help analyze the alarm cause and provide suitable FANUC CNC repair, PSM power supply module checking, MCC contactor troubleshooting, CX48 phase sequence guidance, DC bus short circuit isolation, servo/spindle drive checking, or power supply module replacement support.
Reference Source: Beijing FANUC. This article is based on technical documentation provided by Beijing FANUC. For More Fanuc CNC repair Cases and technical articles, please back to Fanuc Technical Support Center.
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