Troubleshooting / Delta VFD faults

Delta VFD Fault Codes

The fault codes of Delta AC drives, from the current MS300, ME300 and C2000 Plus to the older VFD-M, VFD-B, VFD-F and VFD-E: what each one means, which series use it, the likely causes, the first checks in order, and how to log it.

How faults show on a Delta drive

When a Delta drive trips, the keypad shows the fault code (for example ocA or GFF), the drive shuts off its output and the motor coasts; on the optional KPC-CC01 LCD keypad the backlight blinks until the fault or warning is cleared.

A warning such as oH1, CE10, AnL or PHL also shows its code, but the drive keeps running, and most warnings clear by themselves once the cause is gone; on MS300, ME300 and C2000 Plus several codes (ot1, uC, oH3, CE10, OPHL, oSL) can be set by parameter to warn or to trip.

On MS300, ME300 and C2000 Plus the last six faults are stored in Pr.06-17 (newest) to Pr.06-22, and MS300 and ME300 keep four more in Pr.14-70 to Pr.14-73. The older drives use different numbers: VFD-M keeps three faults in Pr.73 to Pr.75, VFD-B four in Pr.06-08 to Pr.06-11, VFD-F four in Pr.06-11 to Pr.06-14 and VFD-E five starting at Pr.06.08.

After fixing the cause, reset with the STOP/RESET key, with a digital input set to Reset (setting 5 on MS300, setting 05 on VFD-M and VFD-B), or with a reset command over communication. Delta says to wait 5 seconds after the fault has cleared and to make sure the RUN command is off so the motor cannot restart by surprise.

Some hardware faults (cd1 to cd3, Hd0, Hd1, STL1 to STL3) only clear with a power cycle, and over-voltage or low-voltage faults only reset once the DC bus voltage is back in its normal range.

Safety first.
Delta warns that a hazardous charge stays in the DC bus capacitors after the power is switched off, so do not touch the internal circuits or components until the POWER LED is off.

Measure the remaining voltage between +1/DC+ and DC- with a DC voltmeter and do not start wiring until it is below 25 VDC; for inspection of the older VFD-M, Delta says to wait at least 10 minutes after all display lamps have gone out and confirm the capacitors have discharged. Only qualified people who know AC motor drives should install, wire or service the drive.

Follow lockout/tagout and your site's safe-work procedures, and check the manual for your exact model before you act.

Quick lookup

Faults trip the drive and stop the motor, so in OEE they are availability losses; warnings let the drive keep running or only block the next start.

Type a code or a word (overcurrent, overvoltage, low voltage, ground) to filter the list. Older and newer series use different codes for the same fault, so each has its own row.

75 codes

CodeTypeName
ocAFaultOver-current during acceleration
ocdFaultOver-current during deceleration
ocnFaultOver-current during steady (constant speed) operation
ocSFaultOver-current at stop
GFFFaultGround fault
occFaultIGBT short circuit (upper and lower bridge) / IGBT protection
ovAFaultOver-voltage during acceleration
ovdFaultOver-voltage during deceleration
ovnFaultOver-voltage at constant speed
ovSFaultOver-voltage at stop
LvAFaultLow voltage during acceleration
LvdFaultLow voltage during deceleration
LvnFaultLow voltage at constant speed
LvSFaultLow voltage at stop
orPFaultInput phase loss protection
PHLFaultPhase loss (input)
oH1FaultIGBT overheating
oH2FaultKey components overheat
tH1oFaultIGBT temperature detection failure
oLFaultDrive overload
EoL1FaultElectronic thermal relay 1 protection (motor 1)
EoL2FaultElectronic thermal relay 2 protection (motor 2)
oH3FaultMotor overheating (PTC / PT100)
ot1FaultOver-torque 1
ot2FaultOver-torque 2
uCFaultUnder current
cF1FaultEEPROM write error
cF2FaultEEPROM read error
cd1 / cd2 / cd3FaultU, V or W phase current detection error
Hd0 / Hd1Faultcc (current clamp) or oc hardware error
AUEFaultAuto-tuning error
AFEFaultPID feedback loss (ACI)
ACEFaultACI loss (4 to 20 mA input lost)
AnLWarningACI analog signal loss (warning)
EFFaultExternal fault
EF1FaultEmergency stop
bbFaultExternal base block
PcodFaultPassword is locked
CE1WarningModbus illegal command (communication error 1)
CE2WarningModbus illegal data address (communication error 2)
CE3WarningModbus illegal data value (communication error 3)
CE4WarningData written to read-only address (communication error 4)
CE10FaultModbus transmission time-out
dEbFaultDeceleration energy backup
oSLFaultOver slip error
STOFaultSafe Torque Off active
OPHLFaultOutput phase loss (oPL1 / oPL2 / oPL3)
oL3FaultPower module overload (overload at low frequency)
bFFaultBrake transistor fault
ocFaultOver-current (older series)
ovFaultOver-voltage (older series)
LvFaultLow voltage (older series)
oHFaultOverheat (older series)
oL1FaultOverload 1, internal electronic thermal trip (older series)
oL2FaultOverload 2, motor overload by over-torque detection (older series)
cF3FaultCPU / internal detection failure (older series)
HPFFaultHardware protection failure (older series)
codEFaultSoftware or password protection (older series)
cFAFaultAuto acceleration / deceleration failure (older series)
LcFaultUnder current / low current (older series)
AL001FaultOver current (servo)
AL002FaultOver voltage (servo)
AL003FaultUnder voltage (servo)
AL004FaultMotor combination error
AL005FaultRegeneration error
AL006FaultOverload (servo)
AL009FaultExcessive deviation of position command
AL011FaultEncoder error
AL013FaultEmergency stop (servo)
AL014WarningReverse limit error
AL015WarningForward limit error
AL016FaultIGBT overheat (servo)
AL017FaultAbnormal EEPROM
AL022FaultMain circuit power lack phase
AL023WarningEarly warning for overload

Each code: causes and first checks

ocA: Over-current during acceleration

Hits OEE: Availability

What it means: Output current shot far above the drive rating while the motor was speeding up, so the drive cut its output and the motor coasted to a stop.[1][2][3][4][5][6][7]

Also on: MS300, ME300, C2000 Plus, VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Acceleration time (or S-curve) set too short for the load
  • Short circuit or worn insulation in the motor or motor cable
  • Load too large, or a sudden load change, for the drive size
  • A contactor on the drive output (U/V/W) switching while the drive is running
  • V/F voltage or torque compensation set too high

First checks, in this order

  1. Disconnect the motor and megger the motor and cable for shorts and insulation breakdown
  2. Lengthen the acceleration time and retry
  3. Check the motor nameplate current is not above the drive rating and the machine is not jammed
  4. Make sure no output contactor opens or closes while the drive is putting out voltage
  5. Lower torque compensation (Pr.07-26 on MS300) or the V/F voltage if it was raised

ocd: Over-current during deceleration

Hits OEE: Availability

What it means: Output current went far above the drive rating while the motor was slowing down, so the drive cut its output and the motor coasted.[1][2][3][4][5][6][7]

Also on: MS300, ME300, C2000 Plus, VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Deceleration time (or S-curve) set too short
  • Mechanical brake on the motor closing too early
  • Short circuit or worn insulation in the motor or motor cable
  • Drive too small for the load

First checks, in this order

  1. Lengthen the deceleration time and retry
  2. Check the timing of the mechanical brake so it does not grab while the drive is still driving the motor
  3. Megger the motor and motor cable
  4. Compare the running current with the drive rating

ocn: Over-current during steady (constant speed) operation

Hits OEE: Availability

What it means: Output current went far above the drive rating while the motor was running at a set speed, so the drive tripped.[1][2][3][4][5][6][7]

Also on: MS300, ME300, C2000 Plus, VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Short circuit or worn insulation in the motor or motor cable
  • Motor shaft locked or the machine jammed
  • Sudden increase in load
  • Drive output capacity too small for the motor
  • Electrical interference from poor wiring or grounding

First checks, in this order

  1. Check the machine for a jam or a locked motor shaft
  2. Megger the motor and motor cable
  3. Look at what the load was doing at the moment of the trip
  4. Check grounding and keep control wiring away from power wiring

ocS: Over-current at stop

Hits OEE: Availability

What it means: The drive saw over-current, or a fault in its current detection, while it was stopped. If it is a hardware fault, cd1, cd2 or cd3 appears after a power cycle.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Electrical interference on the control or main circuit wiring
  • Hardware failure in the current detection circuit
  • A hardware problem that shows up as cd1 to cd3 after the power is cycled

First checks, in this order

  1. Check grounding and the routing of control and main circuit wiring
  2. Cycle the power and see whether cd1, cd2 or cd3 appears
  3. If a cd code appears, return the drive for repair

GFF: Ground fault

Hits OEE: Availability

What it means: The drive found current leaking to earth from one of its output terminals and shut off. Delta notes this protects the drive, not people.[1][2][3][4][5][6][7]

Also on: MS300, ME300, C2000 Plus, VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Motor winding insulation burnt or aged
  • Damaged motor cable shorting to ground
  • High stray capacitance on a long motor cable
  • Electrical interference
  • Damaged IGBT power module or other drive hardware

First checks, in this order

  1. Disconnect the motor and megger the motor and cable to ground
  2. Inspect the cable and terminal box for damage or moisture
  3. On long cable runs (Delta mentions over 100 m) lower the carrier frequency
  4. Cycle the power after the checks; if GFF stays with a good motor and cable, return the drive

occ: IGBT short circuit (upper and lower bridge) / IGBT protection

Hits OEE: Availability

What it means: The drive detected a short between the upper and lower transistors of its output power module and shut down to protect it.[2][5][6]

Also on: C2000 Plus, VFD-B (IGBT protection), VFD-F (AC drive IGBT fault)

Likely causes

  • IGBT power module fault
  • Fault in the short-circuit detection circuit
  • Short circuit in the motor wiring

First checks, in this order

  1. Check the motor wiring for shorts
  2. Cycle the power
  3. If occ comes back, return the drive for repair

ovA: Over-voltage during acceleration

Hits OEE: Availability

What it means: The DC bus voltage inside the drive rose above its trip level while the motor was speeding up.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Supply voltage too high or voltage spikes on the supply
  • Power factor (phase-in) capacitors switching on the same supply
  • Energy pushed back by a high inertia load
  • Ground fault on the motor cable charging the DC bus
  • Brake resistor or braking unit wired wrong

First checks, in this order

  1. Measure the input voltage and confirm it is inside the drive rating
  2. Check for capacitor banks switching nearby; Delta suggests an AC reactor
  3. Check the motor cable and terminal box for a ground fault
  4. Turn on over-voltage stall prevention (Pr.06-01) and check the brake resistor wiring

ovd: Over-voltage during deceleration

Hits OEE: Availability

What it means: While slowing down, the motor acted as a generator and pushed the DC bus voltage above the trip level.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Deceleration time too short for the load inertia
  • No brake resistor, braking unit or DC bus sharing fitted
  • Supply voltage too high
  • Ground fault on the motor cable
  • Brake resistor or braking unit wired wrong

First checks, in this order

  1. Lengthen the deceleration time (Pr.01-13, 01-15, 01-17, 01-19 on MS300)
  2. Fit or check the brake resistor or braking unit
  3. Turn on over-voltage stall prevention (Pr.06-01)
  4. Measure the supply voltage

ovn: Over-voltage at constant speed

Hits OEE: Availability

What it means: The DC bus voltage went above the trip level while the motor was running at a steady speed.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Sudden load change feeding energy back into the drive
  • Regenerative energy from motor inertia
  • Supply voltage too high or capacitor switching on the supply
  • Ground fault on the motor cable

First checks, in this order

  1. Check whether the load can overhaul (drive the motor) at steady speed
  2. Fit or check the brake resistor or braking unit
  3. Measure the supply voltage
  4. Check the motor cable for a ground fault

ovS: Over-voltage at stop

Hits OEE: Availability

What it means: The DC bus voltage was above the trip level while the drive was stopped, which usually points at the supply rather than the motor.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Supply voltage too high or voltage spikes
  • Power factor (phase-in) capacitors switching on the same supply
  • Brake resistor or braking unit wired wrong
  • Hardware failure in voltage detection

First checks, in this order

  1. Measure the supply voltage with the drive stopped
  2. Check for capacitor banks or other equipment switching on the same supply
  3. Check the brake resistor wiring
  4. Cycle the power; if cd1 to cd3 appear, return the drive

LvA: Low voltage during acceleration

Hits OEE: Availability

What it means: The DC bus voltage dropped below the low voltage level (Pr.06-00) while the motor was speeding up.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Power loss or a weak supply
  • Supply voltage changing
  • A large motor starting on the same supply
  • Load too large
  • No short circuit plate or DC reactor between terminals +1 and +2

First checks, in this order

  1. Measure all three input phases during the start
  2. Check the supply capacity and other big loads on it
  3. Lengthen the acceleration time or reduce the load
  4. Check the plate or DC reactor between +1 and +2 is fitted

Lvd: Low voltage during deceleration

Hits OEE: Availability

What it means: The DC bus voltage dropped below the low voltage level (Pr.06-00) while the motor was slowing down.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Power loss or a weak supply
  • Supply voltage changing
  • A large motor starting on the same supply
  • Sudden load

First checks, in this order

  1. Measure the input voltage
  2. Check for other large loads starting at the same moment
  3. Check the supply capacity
  4. Consider a DC reactor, as Delta suggests

Lvn: Low voltage at constant speed

Hits OEE: Availability

What it means: The DC bus voltage dropped below the low voltage level (Pr.06-00) while the motor was running at a steady speed.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Power loss or a weak supply
  • Supply voltage changing
  • A large motor starting on the same supply
  • Sudden load

First checks, in this order

  1. Measure the input voltage under load
  2. Check for other large loads on the same supply
  3. Reduce the load or use a larger drive if the supply is fine
  4. Consider a DC reactor, as Delta suggests

LvS: Low voltage at stop

Hits OEE: Availability

What it means: The DC bus voltage was below the low voltage level while the drive was stopped, or the voltage detection hardware failed.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Power off or a weak supply
  • Drive model does not match the supply voltage
  • Supply voltage changing
  • A large motor starting on the same supply

First checks, in this order

  1. Check the drive voltage rating matches the supply
  2. Measure the input voltage
  3. Cycle the power after the supply is confirmed good
  4. If LvS stays with a good supply, return the drive

orP: Input phase loss protection

Hits OEE: Availability

What it means: The drive saw too much ripple on its DC bus while loaded, which means one input phase is missing or weak.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Lost input phase or a cut input cable
  • Single phase supply on a three-phase model
  • Loose input power terminals
  • Unbalanced three-phase supply

First checks, in this order

  1. Measure all three input phases at the drive terminals
  2. Tighten the input terminal screws to the torque in the manual
  3. Check the input cable, fuses and main contactor
  4. Review Pr.06-50, Pr.06-52 and Pr.06-53 (input phase loss settings)

PHL: Phase loss (input)

Hits OEE: Availability

What it means: One phase of the input supply is missing. On VFD-B, VFD-F and VFD-E this trips the drive; on MS300 PHL is a warning that clears when the drive stops (the trip there is orP).[5][6][7][1]

Also on: VFD-B, VFD-F, VFD-E (fault); MS300 (warning)

Likely causes

  • Loose contact on an input phase terminal
  • Broken input cable
  • Single phase supply on a three-phase model
  • Unbalanced three-phase supply

First checks, in this order

  1. Check the input phase wiring for loose contacts
  2. Measure all three input phases
  3. Check the main contactor and fuses on the supply
  4. Cycle the power after the supply is normal; if it stays, return the drive

oH1: IGBT overheating

Hits OEE: Availability

What it means: The output power module (IGBT) got hotter than its trip level. Above the warning level set in Pr.06-15 but below the trip level, oH1 shows as a warning and the drive keeps running.[1][2][3][7]

Also on: MS300, ME300, C2000 Plus, VFD-E

Likely causes

  • Cabinet or ambient temperature too high, or blocked ventilation
  • Heat sink blocked or cooling fan stopped
  • Not enough space around the drive
  • Drive overloaded or carrier frequency too high
  • Drive running at 100% or more of rated output for a long time

First checks, in this order

  1. Check the cabinet temperature and the ventilation openings
  2. Check the drive fan runs and the heat sink is clean
  3. Check the clearance around the drive
  4. Reduce the load or the carrier frequency, or move to a larger drive

oH2: Key components overheat

Hits OEE: Availability

What it means: A temperature sensor on key components inside the drive stayed above its protection level, so the drive tripped.[2]

Also on: C2000 Plus

Likely causes

  • Cabinet or ambient temperature too high, or blocked ventilation
  • Heat sink blocked or cooling fan stopped
  • Drive overloaded or carrier frequency too high
  • Unstable power supply
  • Load changing frequently

First checks, in this order

  1. Check the cabinet temperature and ventilation
  2. Check the fan and clean the heat sink
  3. Reduce the load or carrier frequency
  4. Fit a reactor if the supply is unstable, as Delta suggests

tH1o: IGBT temperature detection failure

Hits OEE: Availability

What it means: The drive cannot read its IGBT temperature sensor properly, so it stops to stay safe.[1][2][3]

Also on: MS300, ME300, C2000 Plus (C2000 Plus also has tH2o for the capacitor sensor)

Likely causes

  • Temperature sensor (NTC) broken
  • Wiring failure to the sensor
  • Drive hardware failure

First checks, in this order

  1. Wait 10 minutes, then cycle the power
  2. Check whether tH1o comes back
  3. If it stays, return the drive for repair

oL: Drive overload

Hits OEE: Availability

What it means: The drive has carried more current than its overload curve allows for too long and tripped to protect itself.[1][2][3][4][5][6][7]

Also on: MS300, ME300, C2000 Plus, VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Load too large
  • Acceleration, deceleration or the work cycle too short
  • V/F voltage too high
  • Drive too small for the job
  • Overload during low speed running or torque compensation too high

First checks, in this order

  1. Compare the output current with the drive rating over a full cycle
  2. Lengthen acceleration and deceleration times
  3. Check the V/F curve and torque compensation settings
  4. Lower the carrier frequency or use a larger drive

EoL1: Electronic thermal relay 1 protection (motor 1)

Hits OEE: Availability

What it means: The drive's built-in motor thermal model says motor 1 is overheating from too much current for too long, so the drive coasts to stop.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Load too large or the work cycle too short
  • Standard motor run too long at low speed
  • Wrong motor rated current in the drive
  • Wrong motor type in Pr.06-13, or one drive running several motors
  • Motor fan fault

First checks, in this order

  1. Check the motor rated current setting matches the nameplate
  2. Check Pr.06-13 matches the motor type (standard or inverter duty)
  3. Measure the motor current against the nameplate
  4. Check the motor fan; with several motors on one drive, fit a thermal relay per motor

EoL2: Electronic thermal relay 2 protection (motor 2)

Hits OEE: Availability

What it means: Same as EoL1 but for the second motor set: the thermal model for motor 2 tripped.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Load too large or the work cycle too short
  • Standard motor run too long at low speed
  • Wrong motor 2 rated current
  • Wrong motor type in Pr.06-27, or one drive running several motors
  • Motor fan fault

First checks, in this order

  1. Check motor 2 rated current against the nameplate
  2. Check Pr.06-27 matches the motor type
  3. Measure the motor current
  4. Check the motor fan

oH3: Motor overheating (PTC / PT100)

Hits OEE: Availability

What it means: The motor's PTC or PT100 sensor reports a temperature above the set level. Pr.06-29 decides whether this only warns or trips the drive.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Motor shaft locked or load too large
  • Ambient temperature too high
  • Motor cooling or fan fault
  • Motor run too long at low speed
  • PTC or PT100 not set up or wired correctly

First checks, in this order

  1. Feel and measure the motor temperature and check the motor fan
  2. Check for a jam or a heavy load
  3. Check the PTC or PT100 wiring and the input settings
  4. Check the motor rated current setting matches the nameplate

ot1: Over-torque 1

Hits OEE: Availability

What it means: Output current stayed above the over-torque level (Pr.06-07) for longer than Pr.06-08. With Pr.06-06 at 2 or 4 the drive trips; at 1 or 3 it only warns.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Mechanical jam or overload on the machine
  • Over-torque level or time set too low
  • Acceleration or deceleration too short
  • Motor too small for the load

First checks, in this order

  1. Check the machine for a jam, stiff bearings or a tight chain
  2. Review Pr.06-07 and Pr.06-08
  3. Lengthen acceleration and deceleration times
  4. Compare motor current with the motor rating

ot2: Over-torque 2

Hits OEE: Availability

What it means: Second over-torque detection: current stayed above Pr.06-10 for longer than Pr.06-11. Pr.06-09 decides whether it trips (2 or 4) or warns (1 or 3).[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Mechanical jam or overload
  • Over-torque level or time set too low
  • Acceleration or deceleration too short
  • Motor too small for the load

First checks, in this order

  1. Check the machine for a jam
  2. Review Pr.06-10 and Pr.06-11
  3. Lengthen acceleration and deceleration times
  4. Compare motor current with the motor rating

uC: Under current

Hits OEE: Availability

What it means: Output current stayed below the low current level (Pr.06-71) for longer than Pr.06-72, a sign the motor has lost its load. Pr.06-73 decides whether it trips or only warns.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Motor cable disconnected
  • Lost connection between the motor and its load
  • Low current protection set wrong
  • Load too low

First checks, in this order

  1. Check the motor cable and the coupling between motor and load
  2. Check the load is really there (belt, pump prime, product)
  3. Review Pr.06-71, Pr.06-72 and Pr.06-73

cF1: EEPROM write error

Hits OEE: Availability

What it means: The drive cannot write to its internal parameter memory.[2][4][6][7]

Also on: C2000 Plus, VFD-M, VFD-F, VFD-E (cF1.0, cF1.1)

Likely causes

  • Internal EEPROM cannot be programmed
  • Supply voltage outside the drive rating (VFD-M checklist)
  • Control board memory fault

First checks, in this order

  1. Press RESET
  2. Reset the parameters to factory default
  3. Cycle the power and check the input voltage
  4. If cF1 stays, return the drive for repair

cF2: EEPROM read error

Hits OEE: Availability

What it means: The drive cannot read its internal parameter memory.[1][2][3][4][6][7]

Also on: MS300, ME300, C2000 Plus, VFD-M, VFD-F, VFD-E (cF2.0, cF2.1)

Likely causes

  • Internal EEPROM cannot be read
  • Poor connection between the main control board and the power board (VFD-M checklist)
  • Corrupted parameter data

First checks, in this order

  1. Press RESET
  2. Reset the parameters to factory default
  3. Cycle the power
  4. If cF2 stays, return the drive for repair

cd1 / cd2 / cd3: U, V or W phase current detection error

Hits OEE: Availability

What it means: At power up the drive found that the current sensing for one output phase (cd1 = U, cd2 = V, cd3 = W) is not reading correctly.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Hardware failure in the current detection circuit of that phase
  • Checked at power on, so it shows before any run command
  • Can follow an ocS or ovS trip, which Delta says may be hardware related

First checks, in this order

  1. Switch the power off and on (this fault does not clear from the keypad)
  2. Note which phase is named
  3. If the code returns, send the drive for repair

Hd0 / Hd1: cc (current clamp) or oc hardware error

Hits OEE: Availability

What it means: At power up the drive's hardware protection circuit for current clamp (Hd0) or over-current (Hd1) reported a fault. C2000 Plus adds Hd2 (ov hardware) and Hd3 (occ hardware).[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Hardware failure in the protection circuit
  • Checked at power on
  • Older series show the same faults as HPF codes

First checks, in this order

  1. Note whether Hd0 or Hd1 (or Hd2, Hd3 on C2000 Plus) is shown
  2. Cycle the power (keypad reset does not clear it)
  3. If it returns, send the drive for repair

AUE: Auto-tuning error

Hits OEE: Availability

What it means: Motor auto-tuning stopped with an error, so the drive could not measure the motor.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • STOP pressed during tuning
  • Motor size or motor data (Pr.01-01, Pr.01-02) wrong
  • Motor wired wrong or the shaft locked
  • Output contactor open during tuning
  • Load too large or accel/decel too short

First checks, in this order

  1. Enter the motor nameplate data again
  2. Check the motor wiring and that the output contactor is closed
  3. Free the shaft or uncouple the load
  4. Run auto-tuning again

AFE: PID feedback loss (ACI)

Hits OEE: Availability

What it means: With PID control on, the 4 to 20 mA feedback signal dropped below 4 mA. Pr.08-09 decides whether the drive trips or keeps running with a warning.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • PID feedback cable loose or cut
  • Feedback sensor failed
  • Drive analog input hardware failure

First checks, in this order

  1. Measure the mA signal at the ACI terminal
  2. Tighten the terminal and check the cable
  3. Test or replace the feedback sensor
  4. Review Pr.08-08 and Pr.08-09

ACE: ACI loss (4 to 20 mA input lost)

Hits OEE: Availability

What it means: A 4 to 20 mA analog input dropped below 4 mA and Pr.03-19 is set to stop and show ACE. With Pr.03-19 at 1 or 2 the drive shows the AnL warning instead.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • ACI cable loose or cut
  • External signal device failed
  • Drive hardware failure

First checks, in this order

  1. Measure the mA signal at the ACI terminal
  2. Tighten the terminal and check the cable
  3. Check or replace the device sending the signal

AnL: ACI analog signal loss (warning)

Warning: act before it becomes a stop

What it means: A 4 to 20 mA input dropped below 4 mA, and Pr.03-19 is set to keep running at the last frequency or ramp down instead of tripping. It clears by itself when the signal returns.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • ACI cable loose or broken
  • External signal device error
  • Drive hardware error

First checks, in this order

  1. Measure the mA signal
  2. Tighten the terminals or replace the cable
  3. Check the device sending the signal

EF: External fault

Hits OEE: Availability

What it means: A digital input set to External Fault was switched on by outside equipment, so the drive stopped as set in Pr.07-20 (MS300).[1][2][3][4][5][6][7]

Also on: MS300, ME300, C2000 Plus, VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • An external device (for example an overload relay or interlock) wired to the EF input opened or closed
  • Wiring fault on that input
  • Wrong input function setting

First checks, in this order

  1. Find which input is set to EF and what is wired to it
  2. Clear the external condition so the input returns to normal
  3. Press RESET once the input is clear

EF1: Emergency stop

Hits OEE: Availability

What it means: A digital input set to Emergency Stop turned on, so the drive cut its output at once and the motor coasted.[1][2][3][5][6]

Also on: MS300, ME300, C2000 Plus, VFD-B, VFD-F

Likely causes

  • Emergency stop button or safety chain wired to the EF1 input was activated
  • Wiring fault on that input
  • Wrong input function setting

First checks, in this order

  1. Check why the emergency stop was triggered
  2. Release the input and confirm the system is safe
  3. Press RESET

bb: External base block

Hits OEE: Availability

What it means: A digital input set to Base Block is on, so the drive switched its output off and the motor coasts. The code clears when the input is released and is not stored as a fault.[1][2][3][4][6][7]

Also on: MS300, ME300, C2000 Plus, VFD-M, VFD-F, VFD-E

Likely causes

  • External device or PLC switched on the base block input
  • Wiring fault on that input
  • Wrong input function setting

First checks, in this order

  1. Check what is wired to the base block input
  2. Release the input
  3. Confirm the system is back to normal, then run again

Pcod: Password is locked

Hits OEE: Availability

What it means: A wrong password was entered three times in a row in Pr.00-07, so parameter access is locked.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Wrong password typed three times
  • Password forgotten
  • Someone else set a password on the drive

First checks, in this order

  1. Cycle the power and enter the correct password
  2. If it is forgotten, Delta's procedure is to enter 9999 and press ENTER twice within 10 seconds
  3. Be aware that procedure returns all parameters to default, so record settings first if you can

CE1: Modbus illegal command (communication error 1)

Warning: act before it becomes a stop

What it means: The RS-485 Modbus master sent a function code the drive does not accept. With Pr.09-02 at 0 the drive keeps running and the warning clears when a correct command arrives; CE1 is also in the fault list.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Wrong command from the PLC or HMI
  • Electrical interference on the communication cable
  • Communication settings different from the master (Pr.09-04)
  • Broken or poorly connected cable

First checks, in this order

  1. Check the function code the master sends
  2. Compare Pr.09-04 with the master's settings
  3. Check the cable, shield and grounding; keep it away from power cables

CE2: Modbus illegal data address (communication error 2)

Warning: act before it becomes a stop

What it means: The Modbus master asked for a register address the drive does not have.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Wrong register address in the master program
  • Electrical interference
  • Communication settings different from the master (Pr.09-04)
  • Broken or poorly connected cable

First checks, in this order

  1. Check the register address against the drive's Modbus address list
  2. Compare Pr.09-04 with the master
  3. Check the cable and grounding

CE3: Modbus illegal data value (communication error 3)

Warning: act before it becomes a stop

What it means: The Modbus master sent data the drive will not accept, for example data that is too long.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Wrong data or data length from the master
  • Electrical interference
  • Communication settings different from the master (Pr.09-04)
  • Broken or poorly connected cable

First checks, in this order

  1. Check the value and length the master writes
  2. Compare Pr.09-04 with the master
  3. Check the cable and grounding

CE4: Data written to read-only address (communication error 4)

Warning: act before it becomes a stop

What it means: The Modbus master tried to write to a register that is read only.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Master program writes to a read-only register
  • Electrical interference
  • Communication settings different from the master (Pr.09-04)
  • Broken or poorly connected cable

First checks, in this order

  1. Check which register the master writes to
  2. Compare Pr.09-04 with the master
  3. Check the cable and grounding

CE10: Modbus transmission time-out

Hits OEE: Availability

What it means: No Modbus message arrived within the time-out set in Pr.09-03. Pr.09-02 decides whether the drive warns and keeps running, trips (ramp or coast), or ignores it.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • PLC or HMI stopped sending within the Pr.09-03 time
  • Electrical interference
  • Communication settings different from the master (Pr.09-04)
  • Broken or poorly connected cable

First checks, in this order

  1. Check the master is polling the drive faster than Pr.09-03
  2. Check the cable, connectors and grounding
  3. Compare Pr.09-04 with the master
  4. Reset the drive; Delta notes the fault does not clear by itself

dEb: Deceleration energy backup

Hits OEE: Availability

What it means: With Pr.07-13 turned on, the power dipped or failed and the DC bus fell below the dEb level, so the drive ramped the motor down using the load's own energy.[1][2][7][3]

Also on: MS300, C2000 Plus, VFD-E (fault); ME300 (warning)

Likely causes

  • Unstable supply or a power failure
  • Another large load on the same supply pulling the voltage down
  • Supply too small for the connected loads

First checks, in this order

  1. Check the supply for dips at the time of the event
  2. Move large loads to a different supply or increase supply capacity
  3. Check the Pr.07-13 setting (1 needs a manual reset after 0 Hz, 2 restarts by itself)

oSL: Over slip error

Hits OEE: Availability

What it means: On an induction motor at constant speed, the speed difference went beyond the level in Pr.07-29 for longer than Pr.07-30. Pr.07-31 decides warning or trip.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Motor parameters in group 05 wrong
  • Motor overloaded
  • Pr.07-29, Pr.07-30 or Pr.10-29 set wrong

First checks, in this order

  1. Check the motor data and run auto-tuning
  2. Reduce the load
  3. Review the over slip settings

STO: Safe Torque Off active

Hits OEE: Availability

What it means: The safety inputs S1 or S2 opened, so the drive removed torque from the motor. Related codes STL1, STL2 and STL3 mean the S1 or S2 jumper or internal loop is open or faulty.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Safety circuit (e-stop, guard switch, safety relay) opened S1 to DCM or S2 to DCM
  • Short circuit jumper on S1/S2 to DCM missing
  • Internal safety loop hardware failure (STL codes)

First checks, in this order

  1. Check the safety chain and why it opened
  2. Check the S1, S2 and DCM wiring or jumpers
  3. Close the safety switch, then reset (Pr.06-44 sets manual or automatic reset)
  4. If STL1 to STL3 stay after correct wiring and a power cycle, return the drive

OPHL: Output phase loss (oPL1 / oPL2 / oPL3)

Hits OEE: Availability

What it means: The drive found that one output phase to the motor (U, V or W) is missing. Pr.06-45 decides warning, trip or no action.[1][2][3][7]

Also on: MS300, ME300, C2000 Plus, VFD-E (oPHL1 to oPHL3)

Likely causes

  • Motor cable broken or loose on one phase
  • Unbalanced motor windings
  • Single phase motor on the drive
  • Damaged current sensor in the drive
  • Drive much larger than the motor

First checks, in this order

  1. Check the motor cable and terminals on all three phases
  2. Measure the motor windings for balance
  3. Check the three output currents with a clamp meter
  4. Check the drive size matches the motor

oL3: Power module overload (overload at low frequency)

Hits OEE: Availability

What it means: The drive's power module is close to its load limit, usually while running heavy at low frequency.[1][2][3]

Also on: MS300, ME300, C2000 Plus

Likely causes

  • Load too high for the power module
  • Carrier frequency or ambient temperature too high
  • Current limit too high or acceleration too short
  • Too much output voltage at low frequency in V/F control

First checks, in this order

  1. Reduce the load
  2. Lower the carrier frequency (Pr.00-17) and the ambient temperature
  3. Lengthen acceleration and lower the low-frequency voltage
  4. Move to a larger drive if needed

bF: Brake transistor fault

Hits OEE: Availability

What it means: The built-in brake transistor of the drive is not working correctly.[2]

Also on: C2000 Plus

Likely causes

  • Brake transistor hardware fault
  • Brake resistor with the wrong resistance
  • Brake resistor wired wrong
  • Electrical interference

First checks, in this order

  1. Press RESET once
  2. With power off and the bus discharged, check for a short between B2 and DC- with a meter
  3. Check the brake resistor value and wiring
  4. If bF stays, return the drive

oc: Over-current (older series)

Hits OEE: Availability

What it means: The drive saw an abnormal rise in output current and tripped. This is the general over-current code on the older VFD-M, VFD-B, VFD-F and VFD-E drives.[4][5][6][7]

Also on: VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Motor larger than the drive output
  • Short circuit in U, V, W wiring or to ground
  • Loose contacts between drive and motor
  • Acceleration time too short or excessive load

First checks, in this order

  1. Check the motor power matches the drive
  2. Check U, V, W wiring for shorts and loose contacts
  3. Lengthen the acceleration time
  4. If it trips with the short removed and checks done, return the drive

ov: Over-voltage (older series)

Hits OEE: Availability

What it means: The DC bus voltage went above its maximum allowed value.[4][5][6][7]

Also on: VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Input voltage above the drive rating
  • Voltage transients on the supply
  • Motor regeneration when decelerating too fast
  • Not enough braking power

First checks, in this order

  1. Measure the input voltage
  2. Lengthen the deceleration time
  3. Add or check the brake resistor (and brake unit)
  4. Check the needed braking power is within the specified limits

Lv: Low voltage (older series)

Hits OEE: Availability

What it means: The DC bus voltage fell below its minimum value. On VFD-M a low voltage event is not stored in the fault record.[4][5][6][7]

Also on: VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Input voltage below the drive rating
  • Missing input phase on R, S, T (three-phase models)
  • Abnormal load on the motor

First checks, in this order

  1. Measure the input voltage
  2. Check the R, S, T wiring for a lost phase
  3. Check the motor load

oH: Overheat (older series)

Hits OEE: Availability

What it means: The drive's heat sink temperature sensor detected too much heat.[4][5][6]

Also on: VFD-M, VFD-B, VFD-F (VFD-E shows oH1)

Likely causes

  • Ambient temperature above the specified range
  • Ventilation holes blocked
  • Dirty heat sink fins or a failed fan
  • Not enough space around the drive

First checks, in this order

  1. Check the ambient temperature
  2. Clear the ventilation openings
  3. Clean the heat sink and check the fan
  4. Give the drive the spacing the manual asks for

oL1: Overload 1, internal electronic thermal trip (older series)

Hits OEE: Availability

What it means: The drive's electronic thermal overload for the motor tripped.[4][5][6][7]

Also on: VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Motor overloaded
  • Electronic thermal overload set wrong
  • Motor too small
  • Motor rated current setting lower than the real running current needs

First checks, in this order

  1. Check for motor overload
  2. Check the electronic thermal setting
  3. Check the motor rated current parameter (Pr.52 on VFD-M, Pr.07-00 on VFD-B and VFD-F)
  4. Use a larger motor if needed

oL2: Overload 2, motor overload by over-torque detection (older series)

Hits OEE: Availability

What it means: The motor current passed the over-torque detection level for longer than allowed.[4][5][6][7]

Also on: VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Motor load too high
  • Over-torque detection level or time set too low
  • Mechanical overload on the machine

First checks, in this order

  1. Reduce the motor load
  2. Check the over-torque settings (Pr.60 to Pr.62 on VFD-M, Pr.06-03 to Pr.06-05 on VFD-B, VFD-F and VFD-E)
  3. Check the machine for a jam

cF3: CPU / internal detection failure (older series)

Hits OEE: Availability

What it means: The drive's self check found an internal hardware problem. On VFD-E the sub codes cF3.0 to cF3.4 name it: U, V or W phase error, DC bus error or IGBT temperature sensor error.[4][5][6][7]

Also on: VFD-M, VFD-B, VFD-F, VFD-E (cF3.0 to cF3.4)

Likely causes

  • Phase current detection error (U, V or W)
  • DC bus (OV or LV) detection error
  • Temperature sensor error
  • Control board hardware fault

First checks, in this order

  1. Cycle the power
  2. On VFD-E note the sub code shown
  3. If the code returns, send the drive for repair (Delta: return to the factory)

HPF: Hardware protection failure (older series)

Hits OEE: Availability

What it means: A hardware protection circuit inside the drive failed. On VFD-E it shows as HPF1 (CC or OC hardware), HPF2 (OV hardware), HPF3 (GFF hardware) or HPF4 (OC hardware).[4][5][6][7]

Also on: VFD-M, VFD-B, VFD-F, VFD-E (HPF1 to HPF4)

Likely causes

  • Current clamp (CC) or over-current hardware circuit fault
  • Over-voltage hardware circuit fault
  • Ground fault hardware circuit fault

First checks, in this order

  1. Cycle the power
  2. Note the HPF number on VFD-E
  3. If it returns, send the drive for repair

codE: Software or password protection (older series)

Hits OEE: Availability

What it means: The drive's software protection tripped. On VFD-B this is also how a locked password shows: the keypad locks until the power is cycled.[4][5][6][7]

Also on: VFD-M, VFD-B, VFD-F, VFD-E

Likely causes

  • Wrong password entered (VFD-B, Pr.00-07 and Pr.00-08)
  • Keypad locked after a wrong password until the power is cycled (VFD-B)
  • Software protection failure inside the drive

First checks, in this order

  1. If a password was entered, cycle the power and enter the correct one
  2. If no password is involved, cycle the power
  3. If codE returns, send the drive for repair

cFA: Auto acceleration / deceleration failure (older series)

Hits OEE: Availability

What it means: The automatic acceleration and deceleration function could not complete the ramp.[4][5][7]

Also on: VFD-M, VFD-B, VFD-E

Likely causes

  • Motor not suited to running on the drive
  • Regenerative energy too large
  • Load changed suddenly

First checks, in this order

  1. Check the motor suits drive operation
  2. Check how much energy the load feeds back when slowing
  3. On VFD-M, Delta's advice is to stop using the auto accel/decel function

Lc: Under current / low current (older series)

Hits OEE: Availability

What it means: The output current dropped below the low current detection level, often because the motor has lost its load.[5][6]

Also on: VFD-B, VFD-F

Likely causes

  • Load current lower than expected
  • Low current detection settings wrong
  • Lost connection between motor and load

First checks, in this order

  1. Check the load current
  2. Check Pr.06-12 to Pr.06-15 on VFD-B
  3. Check the coupling between motor and load

AL001: Over current (servo)

Hits OEE: Availability

What it means: Current in the servo drive's main circuit went well above the motor's instantaneous current, so the servo switched off.[8]

Also on: ASDA servo drive

Likely causes

  • Drive output short circuited
  • Motor wired wrong
  • IGBT abnormal

First checks, in this order

  1. Check the U, V, W wiring between drive and motor for shorts and bare conductors
  2. Check the wiring order follows the manual
  3. If the wiring is good, send the drive to the distributor or Delta
  4. Clear with the ARST digital input

AL002: Over voltage (servo)

Hits OEE: Availability

What it means: The main circuit voltage of the servo drive is higher than allowed.[8]

Also on: ASDA servo drive

Likely causes

  • Main circuit input voltage above the rated value
  • Wrong power system for the drive
  • Servo drive hardware damaged

First checks, in this order

  1. Measure the main circuit input voltage
  2. Check the supply type matches the drive specification
  3. If the voltage is right and the alarm stays, send the drive in
  4. Clear with the ARST digital input

AL003: Under voltage (servo)

Hits OEE: Availability

What it means: The main circuit voltage is lower than allowed, so the servo is switched off.[8]

Also on: ASDA servo drive

Likely causes

  • Main circuit input voltage too low
  • No power on the main circuit
  • Wrong power system for the drive

First checks, in this order

  1. Measure the main circuit voltage
  2. Check the power switch and input wiring
  3. Cycle power to clear (P2-66 Bit2 lets it clear by itself when voltage returns)

AL004: Motor combination error

Hits OEE: Availability

What it means: The drive is connected to a motor it does not match, or cannot read the motor's encoder properly.[8]

Also on: ASDA servo drive

Likely causes

  • Wrong motor for this drive
  • Encoder connector loose
  • Encoder damaged

First checks, in this order

  1. Check the motor model suits the drive
  2. Reseat the encoder connector
  3. Cycle the power to clear; replace the motor if the encoder is faulty

AL005: Regeneration error

Hits OEE: Availability

What it means: The regenerative (braking) resistor control is in error.[8]

Also on: ASDA servo drive

Likely causes

  • Wrong regenerative resistor or external resistor not connected
  • P1-53 not set to zero when no regenerative resistor is used
  • P1-52 or P1-53 set wrong

First checks, in this order

  1. Check the regenerative resistor connection
  2. Check P1-52 (resistance) and P1-53 (capacity)
  3. Set P1-53 to zero if no resistor is fitted
  4. Clear with the ARST digital input

AL006: Overload (servo)

Hits OEE: Availability

What it means: The motor and drive have been overloaded.[8]

Also on: ASDA servo drive

Likely causes

  • Load above the rated value for a long time
  • Control gains set wrong (mechanical vibration) or accel/decel too fast
  • Motor or encoder wired wrong
  • Motor encoder defective

First checks, in this order

  1. Set P0-02 to 12 and watch whether average torque stays over 100%
  2. Check for vibration and slow the accel/decel times
  3. Check U, V, W and encoder wiring
  4. Clear with the ARST digital input

AL009: Excessive deviation of position command

Hits OEE: Availability

What it means: The gap between where the motor was told to be and where it is grew bigger than the allowed limit.[8]

Also on: ASDA servo drive

Likely causes

  • P2-35 (position deviation limit) set too small
  • Gain set too low
  • Torque limit set too low
  • External load too large

First checks, in this order

  1. Check the machine moves freely and the load is within motor capacity
  2. Check torque limit settings
  3. Review gain tuning
  4. Review P2-35, then clear with ARST

AL011: Encoder error

Hits OEE: Availability

What it means: The motor encoder is sending abnormal pulses.[8]

Also on: ASDA servo drive

Likely causes

  • Encoder wired wrong
  • Encoder connector at CN2 loose
  • Bad connection between CN2 and the motor encoder
  • Encoder damaged

First checks, in this order

  1. Check the encoder cable and the CN2 connector
  2. Check the wiring follows the manual
  3. Cycle the power to clear
  4. Replace the motor if the encoder is damaged

AL013: Emergency stop (servo)

Hits OEE: Availability

What it means: The emergency stop input is active, so the servo is switched off.[8]

Also on: ASDA servo drive

Likely causes

  • Emergency stop button pressed
  • Safety circuit wired to the EMGS input opened
  • Wiring fault on the EMGS input

First checks, in this order

  1. Check why the emergency stop was pressed
  2. Release the e-stop; the alarm clears by itself when the EMGS input turns off
  3. Check the EMGS input wiring

AL014: Reverse limit error

Warning: act before it becomes a stop

What it means: The reverse limit switch input is active. The servo stays on.[8]

Also on: ASDA servo drive

Likely causes

  • Axis reached the reverse limit switch
  • Servo system unstable (control parameters or inertia ratio)
  • Limit switch wiring fault

First checks, in this order

  1. Check the axis position and the limit switch
  2. Jog the axis away in the other direction
  3. Clear with ARST or servo off; re-check tuning if it overshoots

AL015: Forward limit error

Warning: act before it becomes a stop

What it means: The forward limit switch input is active. The servo stays on.[8]

Also on: ASDA servo drive

Likely causes

  • Axis reached the forward limit switch
  • Servo system unstable (control parameters or inertia ratio)
  • Limit switch wiring fault

First checks, in this order

  1. Check the axis position and the limit switch
  2. Jog the axis away in the other direction
  3. Clear with ARST or servo off; re-check tuning if it overshoots

AL016: IGBT overheat (servo)

Hits OEE: Availability

What it means: The servo drive's power transistor (IGBT) temperature is too high.[8]

Also on: ASDA servo drive

Likely causes

  • Drive loaded above its rating for a long time
  • Drive output short circuited
  • Motor current too high

First checks, in this order

  1. Check the load and motor current
  2. Check the drive output wiring
  3. Reduce the load or use a larger motor
  4. Clear with the ARST digital input

AL017: Abnormal EEPROM

Hits OEE: Availability

What it means: The drive's processor had an error reading or writing its parameter memory.[8]

Also on: ASDA servo drive

Likely causes

  • A parameter outside its allowed range at power on
  • Error while writing a parameter during operation
  • Wrong drive type setting after a parameter reset
  • Data in ROM damaged

First checks, in this order

  1. Press SHIFT on the panel to see the detail code (for example E320A points to P2-10)
  2. Correct the named parameter and cycle the power
  3. If it happened during operation, clear with ARST
  4. If the detail code is E0001 (ROM data), send the drive in

AL022: Main circuit power lack phase

Hits OEE: Availability

What it means: Only one phase is reaching the servo drive's main circuit power input.[8]

Also on: ASDA servo drive

Likely causes

  • R, S, T power cable loose or not connected
  • Main circuit supply abnormal
  • Drive hardware fault if the supply is good

First checks, in this order

  1. Check the R, S, T wiring and terminals
  2. Measure all input phases
  3. Clear with ARST; if it stays with good power, send the drive in

AL023: Early warning for overload

Warning: act before it becomes a stop

What it means: The drive is close to its overload limit. The servo stays on, but AL006 may follow.[8]

Also on: ASDA servo drive

Likely causes

  • Machine running near overload
  • P1-56 (overload warning level) set low
  • Same root causes as AL006: heavy load, poor tuning or fast accel/decel

First checks, in this order

  1. Check the load and duty cycle, as for AL006
  2. Review P1-56
  3. Clear with the ARST digital input

Log it, or the same alarm comes back

A drive fault stops the motor and with it the conveyor, pump or fan the line depends on, so in OEE terms it is a breakdown. Log the code, the drive and the minutes lost.

  • Reason code: the code plus the drive, for example Delta ocA, mixer 1 drive, so an overcurrent that trips on every heavy start 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 drive faults across brands, fabrico.io has a VFD fault codes guide. A fault code tells you what the drive measured, not what happened at the machine in the seconds before. Fabrico's camera-based OEE software syncs line camera video with machine data, so you can replay the moment the line stopped next to the trip.

Frequently asked questions

Where do I find the fault history on a Delta MS300, ME300 or C2000 Plus drive?

Read parameters Pr.06-17 to Pr.06-22: Pr.06-17 holds the most recent fault, and each value is a number from the fault list (1 = ocA, 2 = ocd, 3 = ocn, 4 = GFF and so on). MS300 and ME300 keep four more records in Pr.14-70 to Pr.14-73. With the optional KPC-CC01 LCD keypad, the Fault Record menu also shows date, time, frequency, current, voltage and DC bus voltage for each fault.

How do I reset a fault on a Delta VFD?

Fix the cause first, then press STOP/RESET on the keypad, switch on a digital input set to Reset, or send a reset command over communication. Delta says to wait 5 seconds after the fault clears and to make sure the RUN command is off, so the motor does not restart by surprise. Hardware faults such as cd1 to cd3, Hd0 or Hd1 only clear with a power cycle.

What is the difference between ocA, ocd and ocn on a Delta drive?

All three are over-current trips, and the last letter says when it happened: A during acceleration, d during deceleration and n at constant speed (ocS is at stop). ocA usually points to too short an acceleration time or a heavy start, ocd to too short a deceleration time or a brake closing too early, and ocn to a jam or a sudden load. Any of them can also be a short or ground fault in the motor or cable, so megger both if the trip keeps coming back.

Why does my Delta drive trip on ovd when it stops the motor?

When the drive slows a heavy or high inertia load, the motor works as a generator and pushes energy into the DC bus. If the deceleration is too fast and there is no brake resistor or braking unit, the bus voltage climbs past the trip level and the drive shows ovd. Lengthen the deceleration time, turn on over-voltage stall prevention (Pr.06-01 on MS300), or fit a correctly sized brake resistor, and check the supply voltage is not too high.

Why will my Delta drive not reset after a fault?

Delta gives two reasons: the condition that caused the fault is still there, or the drive is in a fault state at power on. Over-voltage faults only reset once the DC bus has dropped back below the reset level, EF and EF1 only after the input is released, and a locked password (Pcod) needs a power cycle. Clear the condition first, then reset again.

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. Delta Standard Compact Drive MS300 Series User Manual (DELTA_IA-MDS_MS300_UM_EN_20240430)
  2. Delta High Performance Vector Control Drive C2000 Plus Series User Manual (DELTA_IA-MDS_C2000 Plus_UM_EN_20220831)
  3. Delta Basic Compact Drive ME300 Series User Manual (DELTA_IA-MDS_ME300_UM_EN_20210809)
  4. Delta General Sensorless Vector Control Micro Drives VFD-M Series User Manual (Revision Oct. 2014)
  5. Delta VFD-B Series User Manual (Revision July 2008, BE16, SW V4.08 & V5.00)
  6. Delta VFD-F Series User Manual (VFD-F_M_EN_20110418)
  7. Delta VFD-E Series User Manual (DELTA_IA-MDS_VFD-E_UM_EN_20150302)
  8. Delta Standard AC Servo Drive for General Purpose Applications ASDA-B2 Series User Manual (DELTA_IA-ASD_ASDA-B2_UM_EN_20230421)

See the moment the drive tripped

Fabrico, a light MES with computer vision, syncs camera footage with machine and timeline data, so you can replay the exact moment the line stopped and review the cause next to the drive's fault. 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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