08

Regeneration Excess Alarm

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What does 08 mean?

This alarm occurs in the αi PSR (Power Supply, Resistance Discharge Type) when a spindle motor with a maximum output of 5kW or more is decelerated while an inappropriate 16Ω regenerative discharge unit is used. The unit cannot dissipate the excess regenerative energy.

Repair Steps

  1. 1

    Verify the maximum output of the spindle motor. If it is 5kW or more, the regenerative discharge unit resistance must be 8Ω, not 16Ω.

  2. 2

    Check the installed regenerative discharge unit (refer to Section 3.1.3.8, page 93, for ordering numbers). If it is a 16Ω unit (e.g., A06B-6089-H510, A06B-6089-H500, A06B-6089-H713) and the motor is 5kW or more, replace it with an 8Ω unit (e.g., A06B-6089-H711 or A06B-6089-H712).

  3. 3

    Ensure the forced cooling fan of the regenerative discharge unit (if applicable, e.g., H7xx series units on page 93) is fully operational.

  4. 4

    Review the spindle motor deceleration parameters in the CNC. Adjust them to reduce the regenerated energy if hardware replacement is not immediately feasible.

  5. 5

    Confirm that the spindle deceleration is not excessively rapid or frequent, which could generate high regeneration energy spikes that exceed the unit's capacity.

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Verified technical data. Last updated: March 2026
Source: [PDF] Fanuc Macro B.pdf CNCTar