Troubleshooting / Yaskawa SERVOPACK alarms

Yaskawa SERVOPACK Alarm Codes

The A. alarm and warning codes of Yaskawa Sigma-7, Sigma-5 and Sigma-II SERVOPACK servo amplifiers: what each one means, where the generations differ, the likely causes, the first checks in order, and how to log it.

How alarms show on the SERVOPACK

When a Sigma-5 or Sigma-7 SERVOPACK detects a fault it shows the alarm number on its panel display: on models with the five-digit panel operator the number flashes (Yaskawa's example is 020 flashing for alarm A.020), and on the MECHATROLINK models with a one-digit display the letter A, the dot and each character of the number appear one after another.

Sigma-II SERVOPACKs show the letter A, a dot and two characters (for example A.32), and A.-- on Sigma-II means normal operation, not an alarm.

An alarm means operation must stop now, so the ALM (servo alarm) signal is output and the motor stops (Gr.1 alarms by the dynamic brake by default, Gr.2 alarms by a zero speed stop by default), while an A.9xx warning only says that an alarm may follow and the SERVOPACK keeps running.

Fn000 shows the last ten alarms, the history is kept through an alarm reset and a power off, and Fn006 clears it (A.E50, A.E60 and FL-1 to FL-7 are never stored on Sigma-7).

To reset, remove the cause first and then use the /ALM-RST input (CN1-44 on analog and pulse train models), press UP and DOWN together on the panel operator, press ALARM RESET on the digital operator, click Reset in SigmaWin+ or send the ALM_CLR command on MECHATROLINK models.

Alarms that Yaskawa marks as not resettable and many encoder alarms clear only after the control power is switched off and on, and A.810 or A.820 clear only with the absolute encoder reset (Fn008).

Safety first.
Yaskawa's Sigma-7 manuals say to wait at least six minutes after switching off the power (at least nine minutes for SERVOPACKs with 100 VAC input) and make sure the CHARGE indicator is not lit before wiring or inspection, and never to touch the power terminals while CHARGE is lit because high voltage can remain inside the SERVOPACK. The Sigma-5 manuals give the same CHARGE lamp rule, and the Sigma-II manual says not to touch the power terminals for five minutes after power off and to check that the charge indicator is off before any inspection.

Yaskawa also warns to remove the cause before resetting an alarm, because resetting and running on with the cause still there can damage the equipment or cause a fire. Follow lockout/tagout and your site's safe-work procedures, and check the manual for your exact model before you act.

Quick lookup

Alarms turn the servo off and stop the axis, so in OEE they are availability losses; A.9 warnings let the axis keep running until you act.

Type a code or a word (overload, encoder, overcurrent, regenerative) to filter the list. Sigma-II uses two-character codes (A.71) where Sigma-5 and Sigma-7 use three (A.710), so the Sigma column says which drives use each row.

56 codes

CodeSigmaTypeName
A.0207, 5AlarmParameter Checksum Error
A.0307, 5AlarmMain Circuit Detector Error
A.0407, 5AlarmParameter Setting Error
A.0507, 5AlarmCombination Error
A.1007, 5AlarmOvercurrent Detected
A.3007, 5AlarmRegeneration Error
A.3207, 5AlarmRegenerative Overload
A.3307, 5AlarmMain Circuit Power Supply Wiring Error
A.4007, 5AlarmOvervoltage
A.4107, 5AlarmUndervoltage
A.5107, 5AlarmOverspeed
A.5207, 5AlarmVibration Alarm
A.7107, 5AlarmInstantaneous Overload
A.7207, 5AlarmContinuous Overload
A.730 / A.7317, 5AlarmDynamic Brake Overload
A.7A05AlarmHeat Sink Overheated
A.7A1 / A.7A27AlarmInternal Temperature Error 1 / 2
A.7Ab7, 5AlarmSERVOPACK Built-in Fan Stopped
A.8107, 5AlarmEncoder Backup Alarm
A.8207, 5AlarmEncoder Checksum Alarm
A.8307, 5AlarmEncoder Battery Alarm
A.8407, 5AlarmEncoder Data Alarm
A.8507, 5AlarmEncoder Overspeed
A.8607, 5AlarmEncoder Overheated
A.C107, 5AlarmServomotor Out of Control
A.C807, 5AlarmEncoder Clear Error or Multiturn Limit Setting Error
A.C907, 5AlarmEncoder Communications Error
A.Cb07, 5AlarmEncoder Echoback Error
A.CC07, 5, IIAlarmMultiturn Limit Disagreement
A.d007, 5AlarmPosition Deviation Overflow
A.E607, 5AlarmReception Error in MECHATROLINK Communications
A.Eb17, 5AlarmSafety Function Signal Input Timing Error
A.F107, 5AlarmPower Supply Line Open Phase
A.9007, 5WarningPosition Deviation Overflow (warning)
A.9107, 5WarningOverload (warning)
A.9117, 5WarningVibration (warning)
A.9207, 5WarningRegenerative Overload (warning)
A.9217, 5WarningDynamic Brake Overload (warning)
A.9307, 5WarningAbsolute Encoder Battery Error (warning)
A.9607, 5WarningMECHATROLINK Communications Warning
A.9717, 5WarningUndervoltage (warning)
A.9A07, 5WarningOvertravel
A.02IIAlarmParameter Breakdown
A.10IIAlarmOvercurrent or Heat Sink Overheated
A.32IIAlarmRegenerative Overload
A.40IIAlarmOvervoltage
A.41IIAlarmUndervoltage
A.51IIAlarmOverspeed
A.71IIAlarmOverload: High Load (Instantaneous Peak Load)
A.72IIAlarmOverload: Low Load (Continuous Peak Load)
A.81IIAlarmEncoder Backup Error
A.83IIAlarmAbsolute Encoder Battery Error
A.C9IIAlarmEncoder Communications Error
A.d0IIAlarmPosition Error Pulse Overflow
A.91IIWarningOverload (warning)
A.93IIWarningAbsolute Encoder Battery Warning

Each code: causes and first checks

A.020: Parameter Checksum Error

Hits OEE: Availability

What it means: The settings stored inside the SERVOPACK failed their integrity check, so the drive no longer trusts its own parameters.[1][3]

Also on: Sigma-7 and Sigma-5 (Sigma-5 name: Parameter Checksum Error 1). An alarm reset does not clear it. Sigma-II shows this kind of fault as A.02 Parameter Breakdown.

Likely causes

  • Supply voltage dropped suddenly, or power was switched off while parameters were being written
  • Parameters were written too many times, for example changed constantly by the host controller
  • Noise from the AC supply, the ground line or static electricity
  • Gas, water drops or cutting oil got inside the SERVOPACK
  • Internal SERVOPACK failure

First checks, in this order

  1. Measure the supply voltage and find out whether power was cut during a parameter change
  2. Check whether the host controller writes parameters over and over, and change that method
  3. Initialize the parameters (Fn005) and enter them again from your saved list
  4. Switch power off and on; if the alarm comes back, look at noise and the cabinet conditions, then replace the SERVOPACK

A.030: Main Circuit Detector Error

Hits OEE: Availability

What it means: The circuit that watches the drive's main power section is sending back bad data.[1][3]

Also on: Sigma-7 and Sigma-5. Alarm reset is possible once the cause is removed.

Likely causes

  • Internal SERVOPACK failure
  • Jumper between the DC reactor terminals removed or making poor contact
  • Cable between a DC reactor and the SERVOPACK wired wrong or loose

First checks, in this order

  1. With power off and CHARGE out, check the jumper or the DC reactor wiring on the DC reactor terminals
  2. Correct or tighten that wiring
  3. Reset the alarm and power up; if it comes back with good wiring, replace the SERVOPACK

A.040: Parameter Setting Error

Hits OEE: Availability

What it means: A parameter is outside its allowed range, or it does not fit the drive and motor that are connected.[1][3][4]

Also on: Sigma-7 and Sigma-5. An alarm reset does not clear it. Gear ratio limit: 0.001 to 64,000 on Sigma-7, 0.001 to 4000 on Sigma-5. Sigma-II has A.04 Parameter Setting Error.

Likely causes

  • SERVOPACK and servomotor capacities do not match
  • A recently changed parameter is outside its setting range
  • Electronic gear ratio (Pn20E/Pn210) is outside the allowed range
  • Motor parameter file not written to the linear encoder (linear motors without a Serial Converter Unit)
  • Internal SERVOPACK failure

First checks, in this order

  1. Find the parameters that were changed last and bring them back inside their ranges
  2. Check the electronic gear ratio Pn20E/Pn210
  3. Confirm the SERVOPACK and motor are a valid capacity pair
  4. If every setting is correct, replace the SERVOPACK

A.050: Combination Error

Hits OEE: Availability

What it means: The drive and the motor are not a size pair that Yaskawa allows to run together.[1][3][4]

Also on: Sigma-7 and Sigma-5. Alarm reset is possible. Sigma-II has A.05 Combination Error with the same one quarter to four times rule.

Likely causes

  • SERVOPACK and servomotor capacities do not match (the motor must be between one quarter and four times the SERVOPACK capacity)
  • Encoder failure
  • Motor parameter file not written to the linear encoder (linear motors)
  • Internal SERVOPACK failure

First checks, in this order

  1. Compare the motor and SERVOPACK nameplates against Yaskawa's combination table
  2. If the pair is valid, replace the motor or encoder and see if the alarm returns
  3. If it still occurs, replace the SERVOPACK

A.100: Overcurrent Detected

Hits OEE: Availability

What it means: Too much current went through the drive's power transistors, or the heat sink overheated, and the output was shut off to protect the drive.[1][3]

Also on: Sigma-7 (Overcurrent Detected) and Sigma-5 (Overcurrent or Heat Sink Overheated). An alarm reset does not clear it. Sigma-II equivalent is A.10.

Likely causes

  • Main circuit cable miswired or making poor contact
  • Short circuit or ground fault in the motor cable, inside the motor or inside the SERVOPACK
  • Regenerative resistor miswired, or the dynamic brake used too often (DB overload)
  • Heavy load while the motor was stopped or turning at low speed
  • Noise, or an internal SERVOPACK failure

First checks, in this order

  1. With power off and CHARGE out, check for shorts between U, V and W and between each phase and ground at the cable, the motor and the SERVOPACK terminals
  2. Check the main circuit and regenerative resistor wiring for loose or wrong connections
  3. Look in the alarm history for dynamic brake overload (A.730 or A.731) and check the regenerative load ratio
  4. Check the load and the FG ground wiring; if nothing is found, replace the SERVOPACK

A.300: Regeneration Error

Hits OEE: Availability

What it means: Something is wrong in the circuit that burns off braking energy, or with its resistor or settings.[1][3][4]

Also on: Sigma-7 and Sigma-5. Alarm reset is possible. Sigma-II equivalent is A.30 Regeneration Error Detected.

Likely causes

  • Jumper between B2 and B3 removed on a model that uses the built-in regenerative resistor
  • External regenerative resistor or resistor unit miswired, removed or disconnected
  • Pn600 is not 0 but no external resistor is fitted on a model without a built-in resistor
  • No external regenerative resistor fitted on a large model that needs one
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the B2 to B3 jumper or the external resistor wiring
  2. Check that Pn600 matches what is actually connected
  3. Never fit an external resistor while the B2 to B3 jumper is in place; Yaskawa warns the SERVOPACK will fail
  4. With main power off, switch control power off and on; if the alarm stays, replace the SERVOPACK

A.320: Regenerative Overload

Hits OEE: Availability

What it means: More braking energy came back from the motor than the regenerative resistor can absorb.[1][3]

Also on: Sigma-7 and Sigma-5, Gr.2 stop, alarm reset possible. Warning A.920 comes first. Sigma-II equivalent is A.32.

Likely causes

  • Supply voltage above the specified range
  • Regenerative resistance or resistor capacity too small, or the machine regenerates continuously
  • A load that keeps driving the motor (negative load) caused continuous regeneration
  • Pn600 or Pn603 set smaller than the external resistor actually fitted
  • External regenerative resistance too high

First checks, in this order

  1. Measure the supply voltage
  2. Look at the deceleration profile and any load that pushes the motor during the cycle
  3. Check Pn600 and Pn603 against the resistor that is fitted
  4. Size the resistor again with Yaskawa's SigmaJunmaSize+ capacity selection software

A.330: Main Circuit Power Supply Wiring Error

Hits OEE: Availability

What it means: At main power on, the drive found that its power connection does not match how it is set up.[1][3][4]

Also on: Sigma-7 and Sigma-5. Alarm reset is possible. Sigma-II equivalent is A.33 Main Circuit Wiring Error.

Likely causes

  • Built-in regenerative resistor went open while the supply voltage was high
  • DC power fed in while the drive is set for AC input
  • AC power fed in while the drive is set for DC input
  • Pn600 is not 0 with no external resistor on a model without a built-in resistor
  • Internal SERVOPACK failure

First checks, in this order

  1. Check whether the supply is AC or DC and make the power input setting match it
  2. Measure the regenerative resistor with a meter
  3. Check Pn600 against the resistor wiring
  4. Replace the external resistor if it is open, or the SERVOPACK if the built-in one is

A.400: Overvoltage

Hits OEE: Availability

What it means: The DC voltage inside the main circuit went too high, usually from braking energy or a high supply.[1][3]

Also on: Sigma-7 and Sigma-5. Alarm reset is possible. Sigma-II equivalent is A.40.

Likely causes

  • Supply voltage above the specified range
  • Unstable supply, or a lightning surge
  • AC voltage too high during acceleration or deceleration
  • External regenerative resistance too high for the operating conditions
  • Moment of inertia ratio above the allowed value

First checks, in this order

  1. Measure the supply voltage, including while the axis accelerates and decelerates
  2. Check the regenerative resistor value against the load
  3. Check that the inertia ratio is within the allowed range
  4. Make the deceleration time longer or reduce the load; fit a surge absorber if the supply is unstable

A.410: Undervoltage

Hits OEE: Availability

What it means: The DC voltage in the main circuit dropped too low to keep the motor under control.[1][3]

Also on: Sigma-7 and Sigma-5, Gr.2 stop, alarm reset possible. Warning A.971 comes first. Sigma-II uses A.41 and the old CACR-SR uses A.60 for undervoltage.

Likely causes

  • Supply voltage below the specified range
  • Voltage sagged during operation because the supply is too weak
  • Momentary power interruption
  • SERVOPACK fuse blown
  • Jumper or cable on the DC reactor terminals missing or loose

First checks, in this order

  1. Measure the supply voltage at the SERVOPACK while the machine runs
  2. Check the power wiring and the supply capacity
  3. If Pn509 (momentary power interruption hold time) was changed, set it lower
  4. Check the DC reactor jumper; a blown fuse means correcting the wiring and replacing the SERVOPACK

A.510: Overspeed

Hits OEE: Availability

What it means: The motor turned faster than its maximum allowed speed.[1][3]

Also on: Sigma-7 and Sigma-5. Alarm reset is possible. Sigma-II equivalent is A.51.

Likely causes

  • U, V and W motor phases wired in the wrong order
  • Speed reference above the overspeed detection level
  • Motor overshot its maximum speed because the gain or the reference input gain is set badly
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the U, V, W order between the SERVOPACK and the motor
  2. Check the reference coming from the host and the motor speed waveform
  3. Lower the reference or the speed reference input gain, then adjust the servo gain
  4. If wiring and references are correct, replace the SERVOPACK

A.520: Vibration Alarm

Hits OEE: Availability

What it means: The drive saw abnormal oscillation in the motor speed and stopped the axis.[1][3]

Also on: Sigma-7 and Sigma-5. Alarm reset is possible. A.521 (Autotuning Alarm) is the same kind of fault seen during tuning.

Likely causes

  • Abnormal oscillation in the motor speed, for example from a speed loop gain that is too high
  • Pn103 (moment of inertia ratio) is larger than the real value or was changed a lot
  • Vibration detection level (Pn312 or Pn384) is not suitable

First checks, in this order

  1. Listen for abnormal motor noise and look at the speed and torque waveforms
  2. Lower the speed loop gain Pn100 or the motor speed
  3. Set Pn103 to the real inertia ratio
  4. Set a suitable vibration detection level; Pn310 chooses whether this shows as alarm A.520 or warning A.911

A.710: Instantaneous Overload

Hits OEE: Availability

What it means: The motor ran for several seconds to a few tens of seconds at a torque far above its rating.[1][3]

Also on: Sigma-7 (Instantaneous Overload) and Sigma-5 (Overload: High Load), Gr.2 stop, alarm reset possible. Warning A.910 comes first. Sigma-II equivalent is A.71.

Likely causes

  • Motor or encoder wiring wrong or making poor contact
  • Operation beyond the motor's overload protection characteristics
  • A mechanical problem kept the motor from turning freely and the load climbed
  • Load on the motor shaft above the allowed value
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the motor and encoder wiring and connectors
  2. With power off, check the mechanics for jams or binding
  3. Compare the torque during the move with the motor rating; slow the cycle or use a larger motor
  4. If the mechanics and load are fine, replace the SERVOPACK

A.720: Continuous Overload

Hits OEE: Availability

What it means: The motor ran for a long time at a torque above its rated value.[1][3]

Also on: Sigma-7 (Continuous Overload) and Sigma-5 (Overload: Low Load), Gr.1 stop, alarm reset possible. Warning A.910 comes first. Sigma-II equivalent is A.72.

Likely causes

  • Motor or encoder wiring wrong or making poor contact
  • Duty cycle beyond the motor's overload protection characteristics
  • A mechanical problem made the load too high
  • Load on the motor shaft above the allowed value
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the motor and encoder wiring and connectors
  2. Check the accumulated load ratio (Un009) during a normal cycle
  3. Check the machine for a mechanical problem that adds load
  4. Reduce the load or the cycle rate, or use a larger motor; replace the SERVOPACK only if the load is normal

A.730 / A.731: Dynamic Brake Overload

Hits OEE: Availability

What it means: When the dynamic brake stopped the motor, it had to burn off more energy than its resistor can take.[1][3][4]

Also on: Sigma-7 and Sigma-5, alarm reset possible. Warning A.921 comes first. Sigma-II equivalent is A.73.

Likely causes

  • The motor was turned by an external force
  • Rotating energy at a dynamic brake stop was above the brake resistor capacity (high speed or high inertia)
  • Stops on the dynamic brake happen too often
  • Internal SERVOPACK failure

First checks, in this order

  1. Check how often the axis stops on the dynamic brake, for example servo off or alarm stops at speed
  2. Reduce the command speed or the load inertia
  3. Make sure nothing drives the motor while the servo is off
  4. If the duty is normal, replace the SERVOPACK

A.7A0: Heat Sink Overheated

Hits OEE: Availability

What it means: The heat sink inside a Sigma-5 SERVOPACK went above 100 C.[3][4]

Also on: Sigma-5 only, Gr.2 stop, alarm reset possible. Sigma-7 reports this as A.7A1 or A.7A2. Sigma-II equivalent is A.7A.

Likely causes

  • Air around the SERVOPACK too hot
  • Overload alarms were reset by switching the power off too many times
  • Excessive load, or regeneration beyond what the drive can handle
  • Wrong mounting direction or not enough space around the SERVOPACK
  • Internal SERVOPACK failure

First checks, in this order

  1. Measure the cabinet air temperature next to the drive
  2. Check the alarm history (Fn000) for overload alarms and stop clearing them by power cycling
  3. Check the accumulated load ratio (Un009) and the regenerative load ratio (Un00A)
  4. Check the mounting direction, clearances and cabinet cooling

A.7A1 / A.7A2: Internal Temperature Error 1 / 2

Hits OEE: Availability

What it means: The air around the control board (A.7A1) or the power board (A.7A2) inside a Sigma-7 SERVOPACK is too hot.[1]

Also on: Sigma-7 only, Gr.2 stop, alarm reset possible. Warnings A.912 and A.913 come first. A.7A3 means the temperature sensor circuit itself failed. Sigma-5 uses A.7A0.

Likely causes

  • Air around the SERVOPACK too hot
  • Overload alarms were reset by switching the power off too many times
  • Excessive load, or regeneration beyond the drive's capacity
  • Wrong mounting direction or not enough space around the SERVOPACK
  • Internal SERVOPACK failure

First checks, in this order

  1. Measure the cabinet air temperature with a thermometer or read the SERVOPACK installation environment monitor
  2. Check the alarm display for overload alarms and change how they are being reset
  3. Check the accumulated load ratio and the regenerative load ratio during a normal cycle
  4. Check the mounting direction and clearances against the manual

A.7Ab: SERVOPACK Built-in Fan Stopped

Hits OEE: Availability

What it means: The cooling fan inside the SERVOPACK has stopped turning.[1][3]

Also on: Sigma-7 and Sigma-5, alarm reset possible. Sigma-7 also has warning A.923 for the same fan.

Likely causes

  • The built-in cooling fan stopped
  • Foreign matter inside the SERVOPACK blocking the fan
  • Internal SERVOPACK failure

First checks, in this order

  1. Power off, wait for CHARGE to go out, and look for debris in the fan
  2. Remove the foreign matter and power up again
  3. If the alarm stays, replace the SERVOPACK

A.810: Encoder Backup Alarm

Hits OEE: Availability

What it means: The absolute encoder lost power from both the drive and the battery, so its turn count (multiturn data) is gone.[1][2][3]

Also on: Sigma-7 (Encoder Backup Alarm) and Sigma-5 (Encoder Backup Error). /ALM-RST, ALM_CLR and the alarm reset key cannot clear it; only the encoder reset does. Sigma-II equivalent is A.81.

Likely causes

  • Absolute encoder powered for the first time (a batteryless absolute encoder always shows it on its first power up)
  • Encoder cable unplugged and plugged back in
  • Neither the SERVOPACK +5 V nor the battery was supplying the encoder
  • Absolute encoder failure
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the battery and the encoder connector
  2. Replace the battery if it is low
  3. Run the absolute encoder reset (Fn008) with the servo off
  4. Set the machine reference position again in the host controller, because the reset changes the multiturn data
  5. If the alarm comes back after the reset, replace the motor

A.820: Encoder Checksum Alarm

Hits OEE: Availability

What it means: The encoder's internal memory failed its self check.[1][3][4]

Also on: Sigma-7 and Sigma-5 (Encoder Checksum Error). An alarm reset does not clear it. Sigma-II equivalent is A.82.

Likely causes

  • Encoder failure found by the encoder's own self diagnosis
  • Absolute encoder data that needs an absolute encoder reset
  • Internal SERVOPACK failure

First checks, in this order

  1. With an absolute encoder, run the absolute encoder reset (Fn008) and set the home position again
  2. If it comes back, replace the motor (encoder)
  3. With an incremental or single-turn encoder, replace the motor
  4. If a known good motor shows it too, replace the SERVOPACK

A.830: Encoder Battery Alarm

Hits OEE: Availability

What it means: When the control power came on, the absolute encoder battery voltage was below the minimum.[1][3]

Also on: Sigma-7 (Encoder Battery Alarm) and Sigma-5 (Absolute Encoder Battery Error), alarm reset possible. Pn008 decides whether a low battery gives alarm A.830 or warning A.930. Sigma-II equivalent is A.83.

Likely causes

  • Battery not connected or making poor contact
  • Battery voltage below 2.7 V
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the battery connection at the host controller or the battery case
  2. Measure the battery voltage
  3. Replace the battery with only the control power ON so the position data is kept
  4. Switch the control power off and on to clear A.830

A.840: Encoder Data Alarm

Hits OEE: Availability

What it means: The data inside the encoder is wrong.[1][3]

Also on: Sigma-7 and Sigma-5 (Encoder Data Error). An alarm reset does not clear it. Sigma-II equivalent is A.84.

Likely causes

  • Encoder malfunction
  • Encoder malfunction caused by noise
  • Error reading data from a linear encoder

First checks, in this order

  1. Switch the SERVOPACK power off and on
  2. Separate the encoder cable from the motor power cable and check the grounding
  3. If the alarm repeats, replace the motor or the linear encoder

A.850: Encoder Overspeed

Hits OEE: Availability

What it means: The encoder was already turning fast when its control power came on.[1][3][4]

Also on: Sigma-7 and Sigma-5. An alarm reset does not clear it. Sigma-II equivalent is A.85 with the same 200 min-1 limit.

Likely causes

  • A rotary motor was turning at 200 min-1 or more when control power came on
  • Encoder malfunction caused by noise
  • Encoder failure
  • Internal SERVOPACK failure

First checks, in this order

  1. Make sure the axis is standing still before the control power is switched on
  2. Check that the load is not turning the motor at power up (Sigma-5 motor speed monitor Un000)
  3. Separate the encoder cable from the main circuit cable and check grounding
  4. Power cycle; if it remains, replace the motor, then the SERVOPACK

A.860: Encoder Overheated

Hits OEE: Availability

What it means: The temperature inside the motor encoder is too high.[1][3][4]

Also on: Sigma-7 and Sigma-5 (not detected on SGMCS direct drive motors). An alarm reset does not clear it. Sigma-II equivalent is A.86.

Likely causes

  • Air around the servomotor too hot
  • Motor load above the rated load
  • Encoder failure
  • Internal SERVOPACK failure

First checks, in this order

  1. Measure the air temperature around the motor; Yaskawa asks for 40 C or less
  2. Check the accumulated load ratio and bring the load within rating
  3. Power cycle; if it remains, replace the motor, then the SERVOPACK

A.C10: Servomotor Out of Control

Hits OEE: Availability

What it means: At servo on the motor moved in a way the drive did not command, so it shut down to prevent a runaway.[1][3][4]

Also on: Sigma-7 (Servomotor Out of Control) and Sigma-5 (Servo Overrun Detected), alarm reset possible. Sigma-II and CACR-SR show A.C1.

Likely causes

  • U, V and W phases wired in the wrong order
  • Wrong Pn080 motor phase sequence setting (linear motors)
  • Encoder failure
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the U, V, W order between the SERVOPACK and the motor
  2. On linear motors, check Pn080
  3. If the wiring is right and the alarm returns after a power cycle, replace the motor
  4. If a good motor shows it too, replace the SERVOPACK

A.C80: Encoder Clear Error or Multiturn Limit Setting Error

Hits OEE: Availability

What it means: The absolute encoder's turn count could not be cleared or set correctly.[1][3][4]

Also on: Sigma-7 and Sigma-5 (Absolute Encoder Clear Error and Multiturn Limit Setting Error). An alarm reset does not clear it. Sigma-II equivalent is A.C8.

Likely causes

  • The multiturn data was not cleared or set correctly during an absolute encoder reset or a multiturn limit change
  • Encoder failure
  • Internal SERVOPACK failure

First checks, in this order

  1. Switch the power off and on and repeat the absolute encoder reset with the servo off
  2. If the alarm returns, replace the motor
  3. If a good motor shows it too, replace the SERVOPACK

A.C90: Encoder Communications Error

Hits OEE: Availability

What it means: The SERVOPACK cannot talk to the motor encoder.[1][3]

Also on: Sigma-7 and Sigma-5. An alarm reset does not clear it; switch the control power off and on after the repair. Sigma-II equivalent is A.C9.

Likely causes

  • Encoder connector loose or miswired
  • Encoder cable broken or shorted, or its impedance outside the specified values
  • Corrosion, water drops or cutting oil, or vibration loosening the connector
  • Noise on the encoder cable
  • Encoder or SERVOPACK failure

First checks, in this order

  1. Reseat and inspect the encoder connector at both ends
  2. Check the encoder cable for damage, the wrong cable type or too much length
  3. Route the encoder cable away from the motor power cable and check the grounding
  4. Move the motor to another SERVOPACK: if the alarm follows the motor replace the motor, if not replace the SERVOPACK

A.Cb0: Encoder Echoback Error

Hits OEE: Availability

What it means: The data coming back from the encoder does not match what was sent, so the link cannot be trusted.[1][3][4]

Also on: Sigma-7 and Sigma-5. An alarm reset does not clear it. Sigma-II equivalent is A.Cb, where the encoder cable limit is 20 m.

Likely causes

  • Encoder wired wrong or making poor contact
  • Encoder cable not to specification and picking up noise
  • Encoder cable too long (50 m max for rotary motors on Sigma-7 and Sigma-5, 20 m for Sigma-7 linear motors)
  • FG potential shifted by machines on the motor side such as welders
  • Excessive vibration or shock on the encoder

First checks, in this order

  1. Check the encoder wiring and connectors
  2. Use a shielded twisted pair encoder cable of at least 0.12 mm2 and stay within the length limit
  3. Ground the machine separately from the encoder FG
  4. Power cycle; if it remains, replace the motor, then the SERVOPACK

A.CC0: Multiturn Limit Disagreement

Hits OEE: Availability

What it means: The multiturn limit stored in the encoder is different from the one set in the SERVOPACK (Pn205).[1][3][4]

Also on: Sigma-7, Sigma-5 and Sigma-II (A.CC). An alarm reset does not clear it; Fn013 does.

Likely causes

  • Pn205 (Multiturn Limit) was changed in the SERVOPACK
  • The multiturn limit in the encoder was never set or was changed
  • Internal SERVOPACK failure

First checks, in this order

  1. Check that Pn205 holds the value the machine needs
  2. Run Fn013 (multiturn limit setting) so the encoder takes the same value as Pn205
  3. Power cycle; if it remains, replace the SERVOPACK

A.d00: Position Deviation Overflow

Hits OEE: Availability

What it means: The motor fell further behind the position command than the limit in Pn520 allows (following error too big).[1][3][4]

Also on: Sigma-7 (Position Deviation Overflow) and Sigma-5 (Position Error Overflow), alarm reset possible. Warning A.900 comes first. Sigma-II equivalent is A.d0, with the level in Pn505.

Likely causes

  • Motor U, V, W wiring faulty
  • Position command speed too high
  • Position reference acceleration too high
  • Pn520 alarm level too low for the operation
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the motor power and encoder wiring for loose contacts
  2. Lower the command speed or acceleration, or smooth it with a position reference filter
  3. Check that Pn520 suits the move
  4. Check the gain tuning and that the load is within the motor rating

A.E60: Reception Error in MECHATROLINK Communications

Hits OEE: Availability

What it means: The drive kept missing data from the MECHATROLINK network.[1][3]

Also on: MECHATROLINK models only: Sigma-7 SGD7S with MECHATROLINK-III and Sigma-5 SGDV with MECHATROLINK-II (Sigma-5 name: MECHATROLINK Communications Error, Reception error). Gr.2 stop, alarm reset possible. On Sigma-7 it is not stored in the alarm history.

Likely causes

  • MECHATROLINK cable wired wrong, or the terminator not fitted correctly
  • Data reception errors caused by noise
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the MECHATROLINK cable connections and the terminator
  2. Check the cable and the FG wiring, and fit a ferrite core on the MECHATROLINK cable
  3. Power cycle; if it keeps happening, replace the SERVOPACK

A.Eb1: Safety Function Signal Input Timing Error

Hits OEE: Availability

What it means: The two hard wire base block safety inputs (/HWBB1 and /HWBB2) did not switch together.[1][3]

Also on: Sigma-7 and Sigma-5. An alarm reset does not clear it.

Likely causes

  • The delay between /HWBB1 and /HWBB2 switching was ten seconds or more
  • Faulty output circuit or device that drives /HWBB1 or /HWBB2
  • Broken input signal cable on one channel
  • Faulty SERVOPACK input circuit

First checks, in this order

  1. Measure the time between /HWBB1 and /HWBB2 switching
  2. Check the safety device outputs and the wiring of both channels
  3. If both signals switch together and the alarm remains, replace the SERVOPACK

A.F10: Power Supply Line Open Phase

Hits OEE: Availability

What it means: One of the three main power phases (R, S or T) stayed low for more than one second while main power was on.[1][3][4]

Also on: Sigma-7 (Power Supply Line Open Phase) and Sigma-5 (Main Circuit Cable Open Phase), Gr.2 stop, alarm reset possible. Sigma-II equivalent is A.F1.

Likely causes

  • Three-phase supply wiring wrong or loose
  • Three-phase supply unbalanced
  • Single-phase power fed in without setting the drive for single-phase input (Pn00B)
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the main power wiring and terminals on all three phases
  2. Measure the voltage of each phase
  3. If the machine runs on single phase, set the single-phase input parameter
  4. Power cycle; if it remains, replace the SERVOPACK

A.900: Position Deviation Overflow (warning)

Warning: act before it becomes a stop

What it means: The following error passed the warning level, which is a percentage of the A.d00 alarm level (Pn520 x Pn51E/100).[1][3][4]

Also on: Sigma-7 and Sigma-5 (Position Error Overflow). Sigma-II equivalent is A.90, set with Pn51E.

Likely causes

  • Motor U, V, W wiring faulty
  • Servo gain too low
  • Position reference acceleration too high
  • Warning level (Pn520 x Pn51E/100) too low for the operation
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the motor and encoder wiring
  2. Check the gains and raise them, for example with autotuning
  3. Lower the reference acceleration or smooth it with a filter
  4. Set Pn520 and Pn51E to suit the operation

A.910: Overload (warning)

Warning: act before it becomes a stop

What it means: The motor is heading toward an overload alarm (A.710 or A.720); it keeps running, but will trip if the load stays high.[1][3]

Also on: Sigma-7 and Sigma-5. Sigma-II equivalent is A.91.

Likely causes

  • Motor or encoder wiring wrong or making poor contact
  • Operation beyond the motor's overload protection characteristics
  • A mechanical problem made the load too high
  • Overload warning level (Pn52B) not suitable
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the motor and encoder wiring
  2. Look for mechanical binding and compare the load torque with the motor rating
  3. Check the overload warning level Pn52B
  4. Reduce the load or the cycle rate, or use a larger motor

A.911: Vibration (warning)

Warning: act before it becomes a stop

What it means: The drive sees abnormal vibration while the motor runs, at the same level that would trigger A.520.[1][3]

Also on: Sigma-7 and Sigma-5.

Likely causes

  • Abnormal vibration during motor operation
  • Pn103 (moment of inertia ratio) larger than the real value or changed a lot
  • Vibration detection level (Pn312 or Pn384) not suitable

First checks, in this order

  1. Listen for abnormal motor noise and check the speed and torque waveforms
  2. Lower the motor speed or reduce the servo gain with custom tuning
  3. Set Pn103 to the real inertia ratio
  4. Set a suitable vibration detection level; Pn310 chooses alarm or warning

A.920: Regenerative Overload (warning)

Warning: act before it becomes a stop

What it means: Braking energy is building up toward a regenerative overload alarm (A.320).[1][3][4]

Also on: Sigma-7 and Sigma-5. Sigma-II equivalent is A.92.

Likely causes

  • Supply voltage above the specified range
  • Regenerative resistance, resistor capacity or SERVOPACK capacity too small, or continuous regeneration
  • A load that keeps driving the motor (negative load)

First checks, in this order

  1. Measure the supply voltage
  2. Check the deceleration profile and any load that pushes the motor
  3. Size the regenerative resistor again with SigmaJunmaSize+

A.921: Dynamic Brake Overload (warning)

Warning: act before it becomes a stop

What it means: Dynamic brake stops are using up the brake resistor's capacity and an A.731 alarm may follow.[1][3]

Also on: Sigma-7 and Sigma-5.

Likely causes

  • The motor was turned by an external force
  • Rotating energy at a dynamic brake stop was above the resistor capacity
  • Internal SERVOPACK failure

First checks, in this order

  1. Check how often the axis stops on the dynamic brake
  2. Reduce the command speed or the load inertia, or stop on the dynamic brake less often
  3. Make sure nothing turns the motor while the servo is off

A.930: Absolute Encoder Battery Error (warning)

Warning: act before it becomes a stop

What it means: The absolute encoder battery is getting low; position is still kept for now.[1][3]

Also on: Sigma-7 and Sigma-5. Pn008 decides whether a low battery shows as warning A.930 or alarm A.830. Sigma-II equivalent is A.93.

Likely causes

  • Battery not connected or making poor contact
  • Battery voltage below 2.7 V
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the battery connection
  2. Measure the battery voltage
  3. Replace the battery with only the control power ON, so the encoder keeps its position

A.960: MECHATROLINK Communications Warning

Warning: act before it becomes a stop

What it means: Communication errors are happening on the MECHATROLINK network, but not yet enough to stop the axis.[1][3]

Also on: MECHATROLINK models only: Sigma-7 SGD7S with MECHATROLINK-III and Sigma-5 SGDV with MECHATROLINK-II.

Likely causes

  • MECHATROLINK cable wired wrong
  • Data reception errors caused by noise
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the MECHATROLINK cable wiring
  2. Check the cable and FG wiring and fit a ferrite core on the MECHATROLINK cable
  3. If the warning keeps coming back, replace the SERVOPACK

A.971: Undervoltage (warning)

Warning: act before it becomes a stop

What it means: The supply voltage is sagging toward an undervoltage alarm (A.410).[1][3]

Also on: Sigma-7 and Sigma-5 (Sigma-5 also lists 280 V or less for 400 V SERVOPACKs).

Likely causes

  • AC supply below 140 V on 200 V SERVOPACKs or below 60 V on 100 V SERVOPACKs
  • Supply voltage dropped during operation
  • Momentary power interruption
  • SERVOPACK fuse blown
  • Internal SERVOPACK failure

First checks, in this order

  1. Measure the supply voltage at the SERVOPACK while the machine runs
  2. Increase the supply capacity if the voltage sags under load
  3. If Pn509 (momentary power interruption hold time) was changed, set it lower
  4. If the fuse is blown, replace the SERVOPACK and fit a reactor

A.9A0: Overtravel

Warning: act before it becomes a stop

What it means: An overtravel limit input (P-OT or N-OT) was seen while the servo was on.[1][3]

Also on: Sigma-7 and Sigma-5. Pn00D (Sigma-7) or Pn008 (Sigma-5) decides whether this warning is detected.

Likely causes

  • The host controller commanded a move into the overtravel limit
  • Overtravel signal wiring fault
  • Noise causing a momentary overtravel signal

First checks, in this order

  1. Check the overtravel signal status on the input signal monitor (Un005 on Sigma-5)
  2. Check the P-OT and N-OT limit switch wiring
  3. Make sure the host program does not command moves past the limits
  4. Take measures against noise if the input monitor shows no overtravel

A.02: Parameter Breakdown

Hits OEE: Availability

What it means: The EEPROM that stores the Sigma-II parameters holds bad data.[4]

Also on: Sigma-II (SGDH and SGDM). An alarm reset does not clear it. On Sigma-5 and Sigma-7 the matching alarm is A.020.

Likely causes

  • Power was switched off while a parameter was being changed
  • Power was switched off while an alarm was being written
  • Parameters were written too many times, for example changed every scan by the host controller
  • SERVOPACK EEPROM or its circuit is faulty

First checks, in this order

  1. Initialize the parameters with Fn005 and enter them again
  2. Check whether the host controller writes parameters every scan and change that method
  3. If the alarm returns, replace the SERVOPACK

A.10: Overcurrent or Heat Sink Overheated

Hits OEE: Availability

What it means: Too much current flowed through the Sigma-II power transistors, or the heat sink overheated.[4]

Also on: Sigma-II. An alarm reset does not clear it. Sigma-5 and Sigma-7 equivalent is A.100; the CACR-SR panel also shows A.10.

Likely causes

  • Short circuit between ground and U, V or W in the motor cable or the motor, or between motor phases
  • Ground wire touching other terminals, or U, V, W wired wrong
  • Dynamic brake used too often, or a dynamic brake stop with large inertia at high speed
  • Overload alarm reset by switching the power off too many times
  • Air around the SERVOPACK above 55 C, fan fault or SERVOPACK fault

First checks, in this order

  1. With power off and the charge lamp out, check for shorts from U, V and W to ground and between phases at the cable and motor
  2. Check the ground wiring at the SERVOPACK terminals
  3. Check how often the dynamic brake is used and reduce the load or speed
  4. Check the cabinet temperature and the drive fan, then replace the SERVOPACK if no outside cause is found

A.32: Regenerative Overload

Hits OEE: Availability

What it means: More braking energy came back from the motor than the Sigma-II regenerative resistor can absorb.[4]

Also on: Sigma-II, alarm reset possible. Warning A.92 comes first. Sigma-5 and Sigma-7 equivalent is A.320.

Likely causes

  • Regenerative energy above the allowed value
  • The machine stayed in a regenerating state too long
  • Pn600 set smaller than the capacity of the external regenerative resistor
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the deceleration and any load that keeps driving the motor
  2. Check Pn600 against the fitted resistor
  3. Choose a larger regenerative resistor or change the operating conditions
  4. Replace the SERVOPACK if the alarm appears at control power on

A.40: Overvoltage

Hits OEE: Availability

What it means: The DC voltage in the Sigma-II main circuit went too high.[4]

Also on: Sigma-II, alarm reset possible. On Sigma-II SERVOPACKs of 22 kW or more, A.40 covers both overvoltage and undervoltage. Sigma-5 and Sigma-7 equivalent is A.400.

Likely causes

  • AC supply voltage too high
  • Large swings in the AC supply voltage
  • High motor speed with too much load inertia, so the regenerative capacity is not enough
  • Internal SERVOPACK failure

First checks, in this order

  1. Measure the AC supply voltage and watch for swings
  2. Check the load inertia and any load that pushes the motor
  3. Lengthen the deceleration or change the operating conditions
  4. Replace the SERVOPACK if the alarm shows at control power on

A.41: Undervoltage

Hits OEE: Availability

What it means: The DC voltage in the Sigma-II main circuit dropped too low.[4]

Also on: Sigma-II. On SERVOPACKs of 22 kW or more the manual reports undervoltage under A.40. Sigma-5 and Sigma-7 equivalent is A.410; CACR-SR uses A.60.

Likely causes

  • AC supply voltage low
  • Large voltage drop or a temporary power failure
  • SERVOPACK fuse blown
  • Inrush current limit resistor open or overloaded from frequent main power switching
  • Internal SERVOPACK failure

First checks, in this order

  1. Measure the AC supply voltage, including under load
  2. Check for short power dips on the supply
  3. Reduce how often the main circuit power is switched on and off
  4. Replace the SERVOPACK if the fuse or inrush resistor has failed

A.51: Overspeed

Hits OEE: Availability

What it means: The Sigma-II motor turned faster than allowed.[4]

Also on: Sigma-II, alarm reset possible. Sigma-5 and Sigma-7 equivalent is A.510; CACR-SR shows A.51 as Feedback Overspeed.

Likely causes

  • U, V and W phases wired in the wrong order
  • Encoder wired wrong
  • Noise on the encoder wiring
  • Position or speed reference too large, or the reference input gain set wrong
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the U, V, W order at the motor
  2. Check the encoder wiring and route it away from power cables
  3. Check the reference and the reference input gain parameter
  4. Replace the SERVOPACK if wiring and references are correct

A.71: Overload: High Load (Instantaneous Peak Load)

Hits OEE: Availability

What it means: The Sigma-II motor ran for several seconds to tens of seconds at a torque far above its rating.[4]

Also on: Sigma-II, alarm reset possible. Warning A.91 comes first. Sigma-5 and Sigma-7 equivalent is A.710.

Likely causes

  • Motor wiring wrong or making poor contact
  • Encoder wiring wrong or connector not fully seated
  • Starting torque above the motor's maximum torque
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the motor wiring
  2. Check the encoder wiring and that the connector is fully inserted
  3. Check the load at start up and the motor capacity
  4. Replace the SERVOPACK if the alarm shows at control power on

A.72: Overload: Low Load (Continuous Peak Load)

Hits OEE: Availability

What it means: The Sigma-II motor ran continuously at a torque above its rating.[4]

Also on: Sigma-II, alarm reset possible. Warning A.91 comes first. Sigma-5 and Sigma-7 equivalent is A.720.

Likely causes

  • Motor wiring wrong or making poor contact
  • Encoder wiring wrong or connector not fully seated
  • Actual torque above the rated torque during normal operation
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the motor and encoder wiring
  2. Compare the load and cycle with the motor rating
  3. Reduce the load or use a larger motor
  4. Replace the SERVOPACK if the load is within rating

A.81: Encoder Backup Error

Hits OEE: Availability

What it means: The Sigma-II absolute encoder lost all its power and its position data was cleared.[4]

Also on: Sigma-II. An alarm reset does not clear it. Sigma-5 and Sigma-7 equivalent is A.810.

Likely causes

  • Absolute encoder powered for the first time
  • Encoder cable was disconnected at some point
  • Neither the PG +5 V supply nor the battery was powering the encoder
  • Absolute encoder fault
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the encoder connection and the battery
  2. Replace the battery if needed
  3. Set up the absolute encoder with Fn008 and set the home position again
  4. If the alarm cannot be cleared by setting up the encoder again, replace the motor

A.83: Absolute Encoder Battery Error

Hits OEE: Availability

What it means: The Sigma-II absolute encoder backup battery voltage has dropped too low.[4]

Also on: Sigma-II, alarm reset possible. Warning A.93 is the early version. Sigma-5 and Sigma-7 equivalent is A.830.

Likely causes

  • Battery connected wrong
  • Battery voltage below 2.7 V
  • Internal SERVOPACK failure

First checks, in this order

  1. Reconnect the battery
  2. Measure and replace the battery
  3. Switch the encoder power (control power) off and on again

A.C9: Encoder Communications Error

Hits OEE: Availability

What it means: The Sigma-II SERVOPACK cannot communicate with the encoder.[4]

Also on: Sigma-II. An alarm reset does not clear it. Sigma-5 and Sigma-7 equivalent is A.C90.

Likely causes

  • Encoder wiring or contacts wrong
  • Encoder cable not the recommended type, or longer than 20 m
  • Noise from a bent or damaged cable, or a cable bundled with power lines
  • FG potential shifted by machines such as welders
  • Encoder or SERVOPACK fault

First checks, in this order

  1. Check the encoder wiring and connectors
  2. Check the cable type and length and replace a damaged cable
  3. Separate the encoder cable from power lines and ground the machine separately from the encoder FG
  4. Replace the motor, then the SERVOPACK, if the alarm remains

A.d0: Position Error Pulse Overflow

Hits OEE: Availability

What it means: The Sigma-II position error (following error) went past the limit set in Pn505.[4]

Also on: Sigma-II, alarm reset possible. Warning A.90 comes first. Sigma-5 and Sigma-7 equivalent is A.d00.

Likely causes

  • Pn505 overflow level set wrong (for example 0)
  • Poor contact in the motor U, V, W wiring
  • Gain adjustment not right
  • Position reference pulse frequency too high
  • Load above the rated load

First checks, in this order

  1. Check the motor U, V, W wiring
  2. Check Pn505 and set a proper level
  3. Raise the speed loop gain (Pn100) and position loop gain (Pn102)
  4. Raise the reference pulse frequency slowly, use smoothing, or correct the electronic gear ratio

A.91: Overload (warning)

Warning: act before it becomes a stop

What it means: The Sigma-II motor is close to an overload alarm (A.71 or A.72) but is still running.[4]

Also on: Sigma-II. Sigma-5 and Sigma-7 equivalent is A.910.

Likely causes

  • Motor wiring wrong or making poor contact
  • Encoder wiring wrong or making poor contact
  • Starting torque above the maximum torque
  • Effective torque above the rated torque
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the motor and encoder wiring
  2. Check the load and operating conditions
  3. Check the motor capacity against the load

A.93: Absolute Encoder Battery Warning

Warning: act before it becomes a stop

What it means: The Sigma-II absolute encoder battery voltage is getting low.[4]

Also on: Sigma-II, checked 4 seconds or more after control power on when Pn002.2 = 0. Sigma-5 and Sigma-7 equivalent is A.930.

Likely causes

  • Battery connection wrong or poor
  • Battery voltage below 2.7 V
  • Internal SERVOPACK failure

First checks, in this order

  1. Check the battery connection
  2. Replace the battery
  3. Switch the encoder power off and on again

Log it, or the same alarm comes back

A servo alarm stops the axis, and on most machines the whole cycle with it, so in OEE terms it is a breakdown. Log the code, the axis and the minutes lost, and count the warnings that come back before an alarm.

  • Reason code: the code plus the axis, for example A.710, press 2 feed axis, so an overload that trips after every die change stands out.
  • Loss bucket: a stop that needs a reset, a part or a technician is an availability loss (breakdown). Stops shorter than your micro-stop threshold go to performance (minor stops). The six big losses page shows where each one belongs.
  • What to count: how often each code fires per week and the minutes it costs. Two numbers a week turn "that alarm comes up sometimes" into a ranked list. The MTBF and MTTR calculator and the downtime cost calculator do the math.

The free OEE tracker logs each stop with its reason and turns the week into a downtime Pareto, so the code that costs the most rises to the top.

For servo motors that keep failing, fabrico.io has a guide to servo motor failure symptoms. An alarm code tells you what the servo drive detected, not what happened at the machine in the seconds before. Fabrico's camera-based OEE software syncs camera video with machine data, so you can replay the moment the axis stopped next to the alarm.

Frequently asked questions

My Yaskawa drive shows A.910. Do I have to stop the machine?

No. A.910 is a warning: the SERVOPACK keeps running, but the motor is close to an overload alarm (A.710 or A.720). Yaskawa lists wiring faults, running beyond the motor's overload characteristics, mechanical problems and an unsuitable Pn52B warning level as the causes. If you keep running without fixing the load, the overload alarm can follow and stop the axis; on Sigma-II the same warning is A.91.

How do I reset an alarm on a Yaskawa SERVOPACK?

Fix the cause first, because Yaskawa warns that resetting and running on can damage the equipment or cause a fire. Then use the /ALM-RST input, press UP and DOWN together on the panel operator, press ALARM RESET on the digital operator, click Reset in SigmaWin+, or send ALM_CLR on MECHATROLINK models. If an alarm will not reset that way, which is common for encoder alarms, Yaskawa says to switch the control power off and on, and A.810 or A.820 only clear with the absolute encoder reset (Fn008).

Why did A.810 appear after I changed the encoder battery?

The absolute encoder keeps its turn count only while it gets power from the SERVOPACK or the battery, so changing the battery with the control power off, or unplugging the encoder cable, wipes the multiturn data. Yaskawa's procedure is to switch on only the control power, swap the battery, then switch the control power off and on to clear A.830. If A.810 is already showing, run the absolute encoder reset (Fn008) with the servo off and set the machine reference position again in the host controller.

Are Sigma-II alarm codes the same as Sigma-5 and Sigma-7 codes?

Sigma-II shows two characters after the dot (A.10, A.32, A.91) while Sigma-5 and Sigma-7 show three (A.100, A.320, A.910), and for the common faults the names in Yaskawa's manuals line up, so A.71 on Sigma-II and A.710 on Sigma-5 and Sigma-7 are both the high load overload. It is not a perfect match: Sigma-II SERVOPACKs of 22 kW or more use A.40 for both overvoltage and undervoltage, and the old CACR-SR uses A.60 for undervoltage. Always check the manual for the model on the nameplate.

I changed a parameter and now the display shows A.941. Is the drive broken?

No. A.941 is a warning that you changed a parameter which only takes effect after the power is switched off and on again. Yaskawa's fix is simply to switch the SERVOPACK power off and on. It is listed on Sigma-5 and Sigma-7 SERVOPACKs with analog voltage and pulse train references.

Sources

Codes and meanings follow the manufacturer documentation below. Wording is ours, simplified for the shop floor; the manual for your exact model and software version wins if it differs.

  1. Σ-7-Series AC Servo Drive Σ-7S SERVOPACK with MECHATROLINK-III Communications References Product Manual (Manual No. SIEP S800001 28Y)
  2. Σ-7-Series AC Servo Drive Σ-7S SERVOPACK with Analog Voltage/Pulse Train References Product Manual (Manual No. SIEP S800001 26W)
  3. AC Servo Drives Σ-V Series User's Manual Design and Maintenance, Rotational Motor, MECHATROLINK-II Communications Reference, SGDV SERVOPACK (Manual No. SIEP S800000 46R)
  4. AC Servo Drives Σ-II Series SGMVH/SGDM/SGDH User's Manual (Manual No. SIEP S800000 59A)

See the moment the axis stopped

Fabrico, a light MES with computer vision, syncs camera footage with machine and timeline data, so you can replay the exact moment the axis stopped and review the cause next to its alarm. Cameras also catch short stops and a line that is switched on but not producing, the losses nobody writes down. Machines connect through a PLC, a Fabrico IoT device or an AI camera.

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Related tools: full troubleshooting directory · OEE calculator · downtime cost · MTBF / MTTR · glossary

OEE essentials: OEE calculator · What is OEE · How to improve OEE · Six big losses · Availability · TEEP · Cost of downtime · OEE benchmark · Free OEE tracker · Free OEE software · How to track downtime · How to implement OEE · Light MES vs full MES