LS L7P Fault Codes &List

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Troubleshoot your LS Electric L7P servo drive with our updated guide. Learn to interpret AL-xx alarm codes, use DriveView 9 for indexing diagnostics, and resolve common encoder/overload trips.

L7P Fault Codes Reference Table

Below is the complete list of protective functions and alarm codes for the L7P series. Please refer to this table to match the code on your drive’s display with the specific diagnostic remedy.

LS L7P Fault Codes &List

LS L7P Fault Codes &List

Fault Code and Meaning Cause and Remedy
AL-10

IPM fault
(Over current H/W)		 Cause:
  • Motor cable error or short.
  • Encoder cable error or short.
  • Parameter setting error (Motor ID/Encoder type).

Remedy:
  • Check if wiring is incorrect or shorted; replace motor cable.
  • Check encoder wiring; replace encoder cable.
  • Verify Motor ID [0x2000] and Encoder type [0x2001] match motor label.
AL-14

Over current
(Over current S/W)		 Cause:
  • Check motor phase resistor.
  • Machine part problem (conflict or binding).
  • Drive error.
  • Error by noise.

Remedy:
  • Perform Motor line resistance test (U-V, V-W, W-U should be several Ω or less); replace motor.
  • Check if there is binding in the equipment.
  • If alarm continues after servo on, replace drive.
  • Check FG wiring condition; match FG wire size with main circuit wire size.
AL-16

Current limit exceeded
(Over current H/W)		 Cause:
  • Drive error.
  • Error by noise.

Remedy:
  • If alarm continues after servo on, replace drive.
  • Check method to improve noise of wiring/installation. check FG wiring.
AL-11

IPM temperature
(IPM overheating)		 Cause:
  • Ambient temperature too high.
  • Continuous Overload alarm.
  • High-frequency operation of regenerative drive.
  • Drive setting direction error.
  • Drive error.

Remedy:
  • Check if surrounding temperature is over 50°C; lower temperature.
  • Check accumulated operate overload percentage [0x2603]; change drive/motor capacity or tune gain.
  • Check regenerative overload [0x2606]; adjust regeneration resistor setting [0x2009] or use external resistor.
  • Refer to wiring and connection manual.
  • If alarm continues, replace drive.
AL-15

Current offset		 Cause:
  • Motor U/V/W phase current offset oversetting.
  • Drive error.

Remedy:
  • Check if U/V/W phase current offset [0x2015~0x2017] are 5% of rated current or higher; rerun adjusting phase current offset.
  • If alarm occurs continually after adjusting offset, replace drive.
AL-21

Continuous overload		 Cause:
  • Sequent operating that exceeds rated load.
  • Motor brake error.

Remedy:
  • Check if driving load rate [0x2603] is below 100%; change drive/motor capacity or tune gain.
  • Check if motor brake is holding; provide supply power to motor brake.
AL-22

Drive temperature 1		 Cause:
  • Ambient temperature.
  • Drive error.

Remedy:
  • Check if surrounding temperature is over 50°C.
  • Check if displayed value [0x260B] differs significantly from surrounding temp; replace drive.
AL-23

Regeneration overload		 Cause:
  • Capacity excess by high frequency or continuous regenerative operation.
  • Parameter setting error.
  • Main power input voltage error.
  • Drive error.

Remedy:
  • Check overload rate [0x2606]; Adjust value on 0x2009 or use braking resistor.
  • Check setting value [0x2009] ~ [0x200E].
  • Check if main power voltage is over 544V; recheck power supply.
  • Check temperature of regenerative resistance; replace drive if faulty.
AL-24

Motor cable open		 Cause:
  • Parameter setting error.
  • Motor cable error (disconnected).
  • Motor error (short circuit).
  • Drive error.

Remedy:
  • Check [0x2015] offset current; process phase current offset control.
  • Check if cable is disconnected; replace motor cable.
  • Check short circuit (U,V,W); replace motor.
  • If alarm persists, replace servo drive.
AL-25

Drive temperature 2		 Cause:
  • Ambient temperature.
  • Drive error.

Remedy:
  • Check if surrounding temperature is over 50°C.
  • Check if displayed value 2 [0x260C] is correct; replace drive.
AL-30

Encoder communication		 Cause:
  • Encoder cable error.
  • Parameter setting Error.

Remedy:
  • Check for disconnection/short; replace encoder cable.
  • Ensure [0x2001], [0x2002] matches motor label information.
AL-31

Encoder cable open		 Cause:
  • Encoder error.

Remedy:
  • If alarm continues after servo on, replace drive or servo motor.
AL-32

Encoder data		 Cause:
  • Drive error.

Remedy:
  • If alarm continues after servo on, replace drive.
AL-33

Motor setting
(Motor ID setting error)		 Cause:
  • Setting Motor ID error.
  • Drive error.

Remedy:
  • Ensure value of [0x2000] is same as application motor label; power off/on after adjusting.
  • If alarm continues after servo on, replace drive.
AL-34

Z Phase open		 Cause:
  • Parameter setting error (Mask settings).
  • Encoder cable error.
  • Encoder error.
  • Drive error.

Remedy:
  • For motors without phase Z, mask AL-34 by setting 14th bit of [0x2014].
  • Wiring incorrect or short; replace encoder cable.
  • If alarm continues, replace drive.
AL-35

Low battery		 Cause:
  • Parameter setting Error (Absolute vs Incremental).
  • Poor battery contact or not connected.
  • Battery voltage is low (< 3.3V).

Remedy:
  • Check absolute value encoder [0x2005] setting.
  • Connect battery rightly.
  • Replace battery.
AL-36

Sinusoidal ENC frequency		 Cause:
  • Encoder cable error (wiring/shield).
  • Parameter setting error.
  • Drive error.

Remedy:
  • Check shield and FG disconnect; replace encoder cable.
  • Check encoder type [0x2001]; Check speed command up to 250kHz.
  • If alarm continues, replace drive.
AL-37

Sinusoidal ENC frequency
(Converter error)		 Cause:
  • Converter error.
  • Encoder error.

Remedy:
  • If alarm continues after servo on, replace drive.
AL-38

Encoder setting error		 Cause:
  • Drive / Motor combination error.
  • Encoder cable error.
  • Encoder error.
  • Drive error.

Remedy:
  • Check brand label code; use motor and drive of same brand.
  • Wiring incorrect or short; replace encoder cable.
  • If alarm continues, replace drive.
AL-39

Preset Error		 Cause:
  • Parameter setting Error (Abs encoder value).
  • Poor battery contact.
  • Initial encoder power supply.

Remedy:
  • Check [0x2005] setting.
  • Connect battery correctly, reset alarm, reapply power. Check mechanical home.
  • Occurs when power applied after first connection; reset alarm and check home.
AL-40

Under voltage		 Cause:
  • Main power input voltage error (Low).
  • Running when power voltage is low.

Remedy:
  • Check if main power is over 134[Vac].
  • Check [0x2605] is over 190 [Vdc].
  • Use 3 phase as supply voltage.
AL-41

Over voltage		 Cause:
  • Main power input voltage error (High).
  • When braking resistor is high.
  • Setting value of acceleration/deceleration.
  • Drive error.

Remedy:
  • Check if main power is below 286[Vac]. Check [0x2605] below 405[Vdc].
  • Review regenerative resistance condition.
  • Set longer acceleration / deceleration time.
  • If alarm continues, replace drive.
AL-42

Main power fail		 Cause:
  • Main power input voltage error (Phase loss).
  • Parameter setting Error (Input mode).
  • Momentary power failure.
  • Drive error.

Remedy:
  • Check voltage between phases (200-230V).
  • Wire or set parameter [0x2006] for correct input power (possibly 3 phase).
  • Check [0x2007] setting.
  • If alarm continues, replace drive.
AL-43

Control power fail		 Cause:
  • Voltage between phase of C1, C2 error.
  • Drive error.

Remedy:
  • Check voltage between phases C1, C2 is within 200-230[Vac].
  • If alarm continues, replace drive.
AL-50

Over speed limit		 Cause:
  • Motor or Encoder cable error.
  • Parameter setting Error (Motor label/Gain).
  • Encoder error.

Remedy:
  • Check wiring; replace cable.
  • Modify parameter [0x2000], [0x2001] to match label.
  • Set Electronic gear ratio low [0x6091] or readjust gain [0x2100].
  • If alarm continues, replace drive.
AL-51

POS following		 Cause:
  • Parameter setting Error.
  • Machine part has problem.
  • Drive error.

Remedy:
  • Check [0x6091] gear ratio. Check [0x6066] position error excess time.
  • Check if machine was forced by drive part.
  • If alarm continues, replace drive.
AL-53

Excessive SPD deviation		 Cause:
  • Motor or Encoder cable error.
  • Parameter setting Error.
  • Machine part has problem.
  • Encoder or Drive error.

Remedy:
  • Check wiring; replace cables.
  • Check [0x2000] matches motor label. Check gear ratio [0x6091].
  • Check operating condition of limit contact point sensor.
  • If alarm continues, replace drive.
AL-63

Parameter checksum		 Cause:
  • When O/S is changed.
  • Drive error.

Remedy:
  • Restore initial parameter (0x1011). Set up parameter before operating.
  • If alarm continues, replace drive.
AL-71

Factory setting		 Cause:
  • Parameter setting error.

Remedy:
  • Contact service center. Check [0x1008] DeviceName.
  • Download OS or set capacity of drive again.
W01

PWR_FAIL
(Main power source loss)		 Cause:
  • Main power input Voltage error.
  • Parameter setting error.
  • Momentary power failure.

Remedy:
  • Check voltage between phase 200-230[Vac] of L1, L2, L3.
  • Check main power input mode [0x2006].
  • Check actual main power or increase value of checking time.
W02

LOW_BATT
(Low voltage of encoder battery)		 Cause:
  • Parameter setting error (Absolute encoder).
  • Bad connection of battery.
  • Battery voltage low.

Remedy:
  • Set [0x2005] to "1" if using ABS encoder as incremental.
  • Connect battery rightly.
  • Replace battery (> 3.3V).
W04

SW_POS_LMT
(Software Position Limit)		 Cause:
  • Parameter setting error (Software restriction).

Remedy:
  • Change value of software position limit [0x2400] or limit value [0x607D].
W10

OV_LOAD
(Operation overload)		 Cause:
  • Sequent operating that exceed rated load.
  • Motor brake error.

Remedy:
  • Check overload warning level [0x2010] and accumulated rate [0x2603]. Tune gain or change capacity.
  • Check if motor brake is holding.
W20

SETUP
(Drive/Motor Combination error)		 Cause:
  • Parameter setting error (Motor ID/Encoder type).
  • Machine part status Error.
  • Motor/Encoder cable error.

Remedy:
  • Modify parameter [0x2000], [0x2001], [0x2002] to match label.
  • Check machine part.
  • Replace motor/encoder cable.
W40

UD_VTG
(Low Voltage)		 Cause:
  • Main power input voltage error (Low).
  • Running when power voltage is low.

Remedy:
  • Check if main power > 134[Vac]. DC link [0x2605] between 190~405[Vdc].
  • Use 3 phase as supply voltage.
W80

EMG
(Emergency signal input)		 Cause:
  • EMG contact error.

Remedy:
  • Emergency stop by EMG contact. Check [0x211F], [0x2200].
 

How to Read L7P Faults via DriveView 9

Because the L7P often handles complex “Indexing” (internal position) tasks, diagnosing it via the LED keypad can be limiting. Connecting your PC via the USB or RS-422 port using DriveView 9 software provides essential 2026 diagnostic data:

  • Alarm History Monitoring: The L7P stores the last 16 alarms in non-volatile memory. DriveView 9 displays these along with the “Accumulated Time” of each occurrence, which is critical for identifying heat-related or power-quality issues.
  • Index Profile Debugging: If you are using Indexing Mode and receive an AL-51 (Position Following Error), the software allows you to graph the target position versus the actual position to see if the error occurs during high-speed moves or deceleration.
  • Object Monitor: Real-time monitoring of DC bus voltage, motor torque, and encoder pulse feedback helps you “see” electrical noise that might be triggering AL-21 (Encoder Communication) faults.

General Troubleshooting Steps for L7P Servos

Before performing a reset, verify these three critical areas of the L7P servo system:

  1. Absolute Encoder Battery (AL-24): If the drive shows AL-24, the absolute position was lost due to a dead backup battery. You must replace the battery and perform an Absolute Encoder Reset to restore your machine’s home position.
  2. Check Mechanical Binding (AL-40): Overload alarms often occur if the motor is undersized or if there is mechanical friction in the ball screw or gearbox. Ensure the Torque Limit parameters are not set too low.
  3. Safe Torque Off (STO): If the display shows “St” or “Safe”, the STO input is open. This is not a fault; it indicates the drive is in a safe standby state. Check your safety relay wiring on the CN1 connector.

Frequently Asked Questions (FAQ)

Q: What is the difference between AL-21 and AL-24?

A: AL-21 is an encoder communication error, usually caused by a broken feedback cable or electrical noise. AL-24 is specifically an “Absolute Position Lost” error, caused by a disconnected or dead encoder battery.

Q: How do I reset a fault on the LS L7P?

A: Once the cause of the alarm is resolved, you can reset the drive by:

  • Pressing the [SET/RESET] key on the front panel.
  • Activating the digital input assigned as the ALMRST (Alarm Reset) signal.
  • Performing a power cycle (Wait for the display to turn off completely before turning it back on).

Q: Why does my drive show “bb” on the display?

A: bb stands for Base Block. This means the drive is healthy but the “Servo-ON” (SVON) signal is not active. The drive is waiting for an enable command before it can move the motor.

Q: Can I use the L7P with a 3rd party motor?

A: The L7P is designed primarily for LS Electric servo motors. If the drive displays AL-31 (Motor Setting Error), it means the motor ID does not match the drive’s internal list. Check the motor code in parameter [P0-00].

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