FANUC SP9033 Alarm 33: DC Link Charge Failure and Troubleshooting

FANUC SP9033 means that the DC power voltage in the power circuit was not charged sufficiently when the magnetic contactor turned on. The CNC displays SP9033 / SSPA:33 SHORTAGE POWER CHARGE, the spindle amplifier displays 33, and the common Power Supply (PS/PSM) normally displays alarm 5.

FANUC lists an open input phase and a defective charging resistor as example causes. Depending on the installed power-supply series, the detailed procedure may also include the input voltage, magnetic contactor and breaker, power-supply monitor connector CX48, PMC contactor timing, number of connected spindle and servo amplifiers, DC-link connections and an internal power-supply failure.

For the surrounding spindle alarm numbers, see the FANUC Serial Spindle Alarm Codes SP9001–SP9033.

What Does FANUC SP9033 Mean?

Before the drive system becomes ready, the common Power Supply charges the capacitors in the shared DC-link circuit. The charging process limits the initial inrush current and must raise the DC-link voltage correctly within the time allowed by the drive control.

SP9033 is issued when the spindle system detects that this charging condition was not achieved when the magnetic contactor was turned on. In the FANUC Series 0i-D/0i Mate-D alarm list, the official examples are an open input phase and a defective charging resistor. The specified actions are to check and correct the power-supply voltage and replace the Power Supply if necessary.

The same electrical condition may be reported at several locations because the Power Supply feeds a common DC link used by connected spindle and servo amplifiers. A machine may therefore show:

• SP9033 on the CNC spindle alarm screen

• 33 on the spindle amplifier

• 5 on the common Power Supply display

• SV0442 CNV. CHARGE FAILURE in the CNC servo alarm list

These indications should be recorded together. They point primarily to the common charging path; they do not by themselves prove that the spindle amplifier is defective.

SP9033, SV0442 and Power Supply Alarm 5

The technician's original draft referred to SV0422. For this condition, the correct related FANUC alarm is SV0442.

FANUC B-64305EN/03 describes SV0442 as a Power Supply converter charge failure involving an abnormal spare or pre-charge circuit for the DC link. The same manual connects SP9033 with Power Supply alarm 5. For the αi Power Supply covered by B-65285EN/04, alarm 5 means that the main-circuit capacitor was not recharged within the specified time.

These codes are related but are not interchangeable labels for every FANUC drive generation. The CNC series, spindle amplifier, Power Supply model and manual edition determine the exact display wording and diagnostic procedure. Confirm every display instead of assuming that a machine showing one code must show all four.

For the related servo-side procedure, see the FANUC SV0442 DC Link Charging Abnormal guide.

1. Confirm the Complete Alarm Combination

Before disconnecting wiring or replacing hardware, record the machine state and all related indications:

• CNC alarm SP9033 / SSPA:33

• Spindle amplifier display 33

• Power Supply display, especially 5

• Any simultaneous SV0442, undervoltage, open-phase or contactor alarm

• Whether all servo axes and the spindle became unavailable together

• Whether the alarm appears at power-on, after emergency-stop release or after recent electrical work

Also record the complete CNC, Power Supply, spindle amplifier and servo-amplifier models, including every suffix. Note the number of connected drive modules and whether a module, Power Supply, contactor, transformer or main-circuit cable was recently added or replaced.

This information is important because FANUC's detailed alarm 5 procedures differ between Power Supply generations. A CX48 check, for example, applies to Power Supplies equipped with that power-supply monitor connector; it is not a universal connector name for every FANUC system.

2. Check the Three-Phase Input Power

FANUC's alarm list first instructs technicians to check and correct the power-supply voltage. With qualified personnel and the appropriate electrical-safety procedure, confirm that the Power Supply receives the specified three-phase AC input.

Check for:

• A missing or open phase

• Low input voltage

• An unbalanced three-phase supply

• A voltage outside the range specified for the exact Power Supply

• A tripped or defective breaker

• Loose, damaged or incorrectly connected main-circuit wiring

Measure the input under the condition in which SP9033 occurs. A no-load measurement made before the contactor operates may not reveal a voltage collapse or missing connection during the charging sequence.

Do not apply generic 200 V- or 400 V-class thresholds from another alarm procedure. The acceptable input range must come from the installed Power Supply specification and machine electrical documentation.

3. Check the Breaker, Magnetic Contactor and Main-Power Sequence

The DC link cannot complete its charge if the Power Supply main circuit is not energized correctly. On applicable systems, confirm that the breaker is on and that the magnetic contactor operates as commanded after emergency stop is released.

Inspect the contactor and its control path for:

• A contactor that does not pull in

• Worn, burnt or high-resistance contacts

• Missing coil power

• A fault in the main-power control circuit

• An interlock or emergency-stop condition preventing operation

• Incorrect feedback to the PMC ladder

The αi-B Power Supply procedure also identifies excessive delay between emergency-stop cancellation and magnetic-contactor power-on as a cause. If the contactor turns on too late, pre-charge may not finish within the specified time. Check the applicable PMC ladder and machine-builder sequence rather than extending or bypassing the protection timer.

Do not force the contactor or defeat the emergency-stop circuit to clear SP9033. The power and safety sequence must operate according to the machine design.

4. Check CX48 Power-Supply Monitor Wiring on Applicable Systems

For αi-B Power Supplies equipped with connector CX48, FANUC's detailed pre-charge procedure requires checking the power-supply monitor input and its cabling.

Confirm that:

• Voltage is supplied to both the Power Supply main circuit and its CX48 monitor circuit

• No CX48 monitor phase is open or disconnected

• The monitored voltage value matches the main-circuit input at L1, L2 and L3

• The CX48 phase sequence matches the main-circuit L1/L2/L3 phase sequence

• The connector and cable are installed according to the machine electrical drawing

The monitor input is not an independent substitute for the main power. The Power Supply compares the monitored supply condition with the main-circuit input. A voltage or phase-sequence mismatch can therefore prevent a valid pre-charge result even when voltage is present at both locations.

CX48 should only be specified when the installed Power Supply and its manual use that connector. On other FANUC Power Supply generations, follow the connector designations and monitoring circuit shown in the corresponding manual.

5. Verify the Number and Capacity of Connected Amplifiers

FANUC lists too many connected servo and spindle amplifier units as a cause of Power Supply alarm 5. The charging circuit may be unable to charge the combined DC-link capacitance within the allowed time when the system configuration exceeds the Power Supply specification.

This check is especially important if SP9033 began after:

• Adding another spindle or servo amplifier

• Retrofitting a higher-capacity drive

• Replacing the original Power Supply with a different rating

• Expanding the number of controlled axes

• Reconfiguring the shared DC-link bus

Compare the complete drive configuration with the applicable FANUC selection and Power Supply manuals. Do not assess suitability only from the Power Supply's physical size or input voltage class. The model, capacity, connected module count and supported system configuration must all be correct.

If the installed Power Supply is undersized or the permitted configuration is exceeded, correct the system selection. Repeated resets will not increase the charging capability.

6. Inspect the DC-Link Connections and Check for a Short Circuit

FANUC identifies a short-circuited DC link as a direct cause of alarm 5. With all power isolated, the required discharge time observed and residual DC voltage verified safe, inspect the shared DC-link path according to the applicable manual.

Check for:

• Loose or incorrectly installed DC-link bars or cables

• A missing connection between the Power Supply and a drive module

• Conductive debris, damaged insulation or incorrect hardware

• A short circuit inside a connected spindle or servo amplifier

• Incorrect DC-link wiring after module replacement or cabinet work

A connected drive module with a shorted DC bus can prevent the Power Supply from charging the entire link. Isolation testing must follow the exact FANUC and machine-builder procedure. Do not remove bus bars, disconnect amplifiers or energize a partially connected system as an improvised test.

The DC link can retain hazardous energy after input power is removed. Only qualified personnel should inspect or measure it, and the charge-indicator LED alone should not replace the required residual-voltage measurement.

7. Evaluate the Charging Resistor and Power Supply Hardware

The 0i-D alarm list names a defective charging resistor as an example cause of SP9033. In B-65285EN/04, a defective recharge-current limiting resistor leads to replacement of the applicable distributing board. Newer αi-B procedures direct the technician to replace the Power Supply after the external supply, monitor wiring, sequence, connected-module count and DC-link conditions have been checked.

This difference should be preserved rather than converted into one universal parts instruction. Depending on the Power Supply series, the supported repair may involve:

• The charging or current-limiting resistor circuit

• A distributing or control board

• The complete Power Supply module

Use the maintenance manual for the exact Power Supply model to determine which assembly is replaceable and how it must be tested. Do not assume that a visibly undamaged resistor is electrically normal, and do not bypass the charging resistor or protection circuit.

If the external power, CX48 circuit where applicable, contactor sequence, module configuration and DC-link wiring are correct but Power Supply alarm 5 remains, professionally test and repair or replace the Power Supply.

If a replacement is required, browse FANUC servo, spindle and power drives or send the complete model and suffix to REACO CNC for compatibility checking.

8. Retest the Complete Drive System

After correcting the confirmed cause, restore the system using the approved startup procedure. Verify that:

• The common Power Supply completes pre-charge and reaches its normal ready display

• PSM alarm 5 no longer appears

• SP9033 and spindle amplifier alarm 33 are cleared

• SV0442 is no longer present

• All servo axes and spindle modules become ready normally

• The contactor and emergency-stop sequence operate correctly

• No abnormal heating, sound, smell or repeated contactor cycling occurs

Begin with the machine builder's controlled no-load test. If another alarm appears, diagnose the new code separately. Do not continue labeling an input open-phase, DC-link undervoltage or spindle-amplifier hardware alarm as SP9033 after the display has changed.

Difference Between SP9033, SP9004 and SP9051

These alarms can all involve the Power Supply, but they describe different detected conditions.

An open phase can contribute to SP9033, but SP9033 specifically concerns the unsuccessful charging result. Always diagnose the exact active display and all simultaneous Power Supply indications.

Difference Between SP9033 and SP9011

SP9033 and SP9011 concern opposite DC-link conditions:

The SP9011 procedure focuses on overvoltage, regenerated energy, Power Supply capacity and supply impedance during motor deceleration. The SP9033 procedure focuses on input power, pre-charge, contactor timing, monitor wiring, connected capacitance and a possible DC-link short circuit. Do not apply SP9011 voltage thresholds or parameter steps to SP9033.

FANUC SP9033 Diagnostic Table

Recommended Troubleshooting Order

1. Confirm SP9033 / SSPA:33, spindle amplifier 33, Power Supply 5 and any related SV0442 indication.

2. Record the complete CNC, Power Supply, spindle and servo amplifier models, suffixes and connected module count.

3. Check the three-phase input for open phase, low voltage, imbalance and out-of-range voltage.

4. Check the breaker, magnetic contactor, main-power control circuit and emergency-stop release sequence.

5. On Power Supplies equipped with CX48, verify monitor voltage, phase presence, value and phase-sequence agreement with L1/L2/L3.

6. Confirm that the number and capacity of connected servo and spindle amplifiers are within the Power Supply specification.

7. With power isolated and residual voltage confirmed safe, inspect the DC-link connections and investigate a possible short circuit using the approved procedure.

8. If all external conditions are correct, test the charging resistor circuit and Power Supply hardware according to the exact model manual.

9. Repair or replace the specified distributing board, supported internal assembly or complete Power Supply.

10. Retest the pre-charge, contactor sequence, all drive-ready states and spindle operation.

Technical References

• FANUC Series 0i-D/0i Mate-D Maintenance Manual, B-64305EN/03, SP9033 / SSPA:33 SHORTAGE POWER CHARGE and SV0442 CNV. CHARGE FAILURE

• FANUC AC Servo Motor αis/αi Series, AC Spindle Motor αi Series, Servo Amplifier αi Series Maintenance Manual, B-65285EN/04, Power Supply Alarm Code 5

• FANUC Servo Amplifier αi-B Series Maintenance Manual, B-65515EN/01, Power Supply pre-charge failure procedure

• Applicable FANUC Power Supply descriptions/selection manual and machine-builder electrical, PMC ladder and service documentation

• Beijing FANUC SP9033 technical guidance, DC link insufficient charging

Always use the manual edition that applies to the exact CNC, Power Supply, spindle amplifier, servo amplifier and machine configuration.

Need Help With FANUC SP9033 Alarm?

REACO CNC provides independent testing, repair, compatibility checking and replacement support for FANUC Power Supply modules, spindle amplifiers and servo amplifiers. Send us the CNC alarm screen, spindle amplifier display, Power Supply display, complete model numbers and suffixes, CX48 and main-power wiring photos where applicable, connected amplifier list, and details of when the alarm occurs.

Visit the FANUC Technical Support Center for more FANUC alarm guides, or contact REACO CNC for assistance.

Reference Source: Beijing FANUC. This article is based on FANUC technical documentation. The correct connector checks, charging-circuit repair, Power Supply replacement and commissioning procedure depend on the exact drive system and machine configuration.