Troubleshooting / Siemens MASTERDRIVES faults

Siemens MASTERDRIVES Fault Codes

The fault (F) and alarm (A) codes of Siemens SIMOVERT MASTERDRIVES drives, vector control (VC) and motion control (MC): what each one means, the likely causes, the first checks with the parameters to look at, and how to log it so it stops coming back.

How faults and alarms show

On the PMU (4-digit seven-segment display) a fault shows as F plus three digits (for example F006) and trips the drive, while an alarm shows as A plus three digits at regular intervals, cannot be acknowledged and clears itself once the cause is gone. On the OP1S the alarm appears in the bottom display line and the red LED flashes.

Fix the cause, then acknowledge with the P (toggle) key while the fault is displayed, with the Reset key on the OP1S (enabled through P565), or with a rising edge on control word 1 bit 7 from the sources P565, P566 and P567 (the PMU always works). A fault that is not reset is still there after the electronics supply is switched off and on, unless auto restart P373 is set.

The fault memory r947 holds the last 8 trips with up to 8 faults each (index 1 to 8 = latest trip, 57 to 64 = oldest, 0 in index 1 = no active fault), r949 holds the matching fault values in the same indices, r782 holds the trip time from the operating hours counter, r951 is the fault text list, and P952 shows the number of stored trips (P952 = 0 clears the memory).

With the fault on display, hold P and press the raise key to jump to the parameter level and read r947 and r949; if several faults or alarms are present, a point appears at the right of the display (sources 1, 2, 4).

Safety first.
Both compendiums warn that the DC link capacitors keep hazardous voltage in the unit for at least 5 minutes after it is disconnected from the supply, so wait at least 5 minutes before opening the unit. The power and control terminals can still carry hazardous voltage even when the motor has stopped (sources 1, 2).

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

Quick lookup

F faults trip the drive and stop the machine, so in OEE they are availability losses; A alarms are warnings and the drive keeps running until you act.

Type a code or a word (overcurrent, DC link, encoder, ground) to filter the list. Click a code for its causes and first checks.

40 codes

CodeTypeName
F001FaultMain contactor checkback
F002FaultPre-charging (VC) / Pre-charging fault (MC)
F006FaultDC link overvoltage
F008FaultDC link undervoltage
F011FaultOvercurrent
F012FaultI too low
F015FaultMotor stall (VC) / Motor blocked (MC)
F017FaultSAFE STOP
F020FaultMotor temperature (VC) / Excess temperature of motor (MC)
F021FaultMotor I2t
F023FaultInverter temperature (VC) / Excess temperature of inverter (MC)
F025FaultUCE upper switch / UCE Ph. L1
F026FaultUCE lower switch / UCE Ph. L2
F027FaultFault pulse resistor / UCE Ph. L3
F028FaultSupply phase
F029FaultMeas. value sensing
F035FaultExt. Fault 1 (VC) / External fault 1 (MC)
F036FaultExt. Fault 2 (VC) / External fault 2 (MC)
F037FaultAnalog input
F042FaultCalculating time (VC) / Time slot overflow (MC)
F051FaultSpeed encoder (VC) / Encoder fault (MC)
F053FaultTachometer dn/dt
F054FaultSensor board initialization fault (VC) / Encoder board initialization fault (MC)
F065FaultSCom telegram failure (VC: Scom Telegram)
F082FaultTB/CB telegram failure
F103FaultGround fault
F255FaultFault in EEPROM
A015AlarmExternal alarm 1
A017AlarmSafe Stop alarm active
A018AlarmEncoder adjustment
A020AlarmOvercurrent (VC); Encoder adjustment, external encoder (MC)
A021AlarmOvervoltage (VC); Encoder data of external multiturn encoder faulty (MC)
A022AlarmInverter temperature
A023AlarmMotor temperature
A025AlarmI2t Inverter (VC) / I2t converter (MC)
A029AlarmI2t motor
A033AlarmOverspeed
A034AlarmSetpoint/actual value deviation
A042AlarmMotor stall/lock (VC) / Motor stall/block (MC)
A084AlarmCB alarm

Each code: causes and first checks

F001: Main contactor checkback

Hits OEE: Availability

What it means: The drive gave the ON command but did not receive the main contactor checkback signal within the time set in P600.[1][2][3][4]

Also on: Same number and name on VC and MC. VC also covers the excitation unit checkback on externally excited synchronous motors. The 1996 VC V1.3 manual used a fixed 500 ms checkback time instead of P600.

Likely causes

  • The main contactor did not close, or its checkback loop (auxiliary contact and wiring) is open
  • P591 points to a binector or input that does not match how the checkback is actually wired
  • Checkback time P600 too short for the contactor
  • VC with an externally excited synchronous motor (P095 = 12): no checkback from the excitation current unit

First checks, in this order

  1. Watch the main contactor after the ON command and confirm it really closes
  2. Trace the checkback loop from the auxiliary contact back to the input selected in P591
  3. Check that P591 matches the real wiring; set it to 0 (MC: P591.B = 0) only if no checkback is wired
  4. If the contactor is slow, increase P600

F002: Pre-charging (VC) / Pre-charging fault (MC)

Hits OEE: Availability

What it means: The DC link did not charge up to its target voltage within the 3 second pre-charging time (VC: 80 % of P071 x 1.34 not reached).[1][2][3][4]

Also on: Same number on VC and MC; MC calls it Pre-charging fault. The 80 % x 1.34 rule is stated in the VC manual.

Likely causes

  • Supply voltage low or missing
  • Blown input fuses (depends on the unit)
  • P071 Line Volts does not match the real supply, or P070 does not match the unit order number (MLFB)
  • On DC-fed units: the rectifier/regenerative unit was not switched on before the inverter

First checks, in this order

  1. Measure the supply voltage (AC or DC) at the drive input and compare it with P071; on DC units compare P071 with the DC link voltage
  2. Check the input fuses
  3. Compare P070 with the order number on the rating plate (MC)
  4. On DC bus systems, switch the rectifier/regenerative unit on before the inverter

F006: DC link overvoltage

Hits OEE: Availability

What it means: The drive shut down because the DC link voltage went above the trip threshold, usually because the motor fed braking energy back into the drive.[1][2][3][4]

Also on: VC trip values: about 410 V (200 to 230 V units), 820 V (380 to 480 V), 1020 V (500 to 600 V) and 1220 V (660 to 690 V); on VC parallel units r949 = 1 means master and 2 means slave. MC gives a rated threshold of 819 V (803 to 835 V with tolerances).

Likely causes

  • Motor regenerating during braking with no braking unit or regenerative feedback
  • Deceleration time P464 too short for the load inertia
  • Supply voltage at the upper tolerance limit; at full load a line phase failure can also cause F006
  • VC: flying restart search speed P526 too high

First checks, in this order

  1. Measure the line voltage or the input DC voltage and compare it with P071
  2. Lengthen the deceleration time P464
  3. VC: activate the DC bus voltage controller P515 (check P071 first), or reduce P259 Max Regen Power when P100 = 3, 4 or 5
  4. MC: read r949, which holds the DC link voltage at the trip (0x7FFF = 1000 V); if fast stops are needed, the drive needs a way to get rid of the braking energy

F008: DC link undervoltage

Hits OEE: Availability

What it means: The DC link voltage fell below 76 % of its normal value (61 % on VC with kinetic buffering), usually because the supply dipped or failed.[1][2][3]

Also on: Same number and name on VC and MC. The 61 % limit with kinetic buffering is VC only.

Likely causes

  • Supply dip or a brief power failure, which may only be detected when power returns
  • Faulty input rectifier on AC-AC units
  • Problem in the DC link or the DC supply on DC-fed units
  • VC with kinetic buffering: speed fell below 10 % of rated motor speed while the DC link was low

First checks, in this order

  1. Measure the line voltage (AC-AC) or input DC voltage (DC-AC) and compare it with P071
  2. Check the input rectifier on AC-AC units
  3. Check the DC link and its connections
  4. MC: read r949 for the DC link voltage at the trip (0x7FFF = 1000 V); where short dips are normal, auto restart P373 can acknowledge F008 automatically, but check that a restart is safe for people

F011: Overcurrent

Hits OEE: Availability

What it means: The output current went above the shutdown threshold and the drive tripped.[1][2][3]

Also on: Same number and name on VC and MC. MC lists F011 as not Compact PLUS and stores the phase in r949; VC has no fault value for it.

Likely causes

  • Short circuit or ground fault at the drive output, in the motor cable or in the motor
  • Mechanical overload of the driven machine
  • Motor and converter not correctly matched
  • Dynamic demands too high (ramps or load steps too steep)

First checks, in this order

  1. Check the converter output, motor cable and motor for short circuit and ground fault
  2. Check the load for overload or jamming
  3. Check that the motor data and the converter rating match
  4. MC: read r949 to see which phase tripped (1 = U, 2 = V, 4 = W; values add up when several phases trip)

F012: I too low

Hits OEE: Availability

What it means: While magnetizing the induction motor, the current stayed below 12.5 % of the no-load magnetizing current setpoint.[1][3]

Also on: VC only, and only in closed-loop n/f/T control (P100 = 3, 4 or 5). Not in the MC fault list. VC F014 (also named I too low, only with U800 = 1) is the similar check for any control type.

Likely causes

  • No motor connected, or the motor circuit is open
  • Fault in the current detection
  • Fault in the power section

First checks, in this order

  1. Check that the motor is connected and any output contactor is closed
  2. If you are testing without a motor, use simulation mode P372
  3. Check the current detection and the power section

F015: Motor stall (VC) / Motor blocked (MC)

Hits OEE: Availability

What it means: The motor is stalled, locked or overloaded, and the condition lasted longer than the time set in P805.[1][2][3]

Also on: Same number, different name. MC can limit detection to standstill (P806 = 1) or switch it off (P806 = 2) and does not detect it on slave drives. VC with synchronous motors also trips on reaching maximum frequency or on wrong excitation current.

Likely causes

  • Static load too high, or a holding brake that did not open
  • Acceleration, deceleration or load changes too fast for the current and torque limits
  • VC: wrong encoder pulse number P151 or analog tacho scaling P138, a broken encoder cable, or a tacho shield that is not connected
  • MC: motor phases connected in the wrong order

First checks, in this order

  1. Check that the machine turns freely and the brake opens
  2. Check current and torque limits; raise them, P805 or P792 only if the load really needs it
  3. VC: check the encoder or tacho cable, its shield at both ends, P151 and P138
  4. MC: check the motor phase connection and sequence; with v/f control, reduce the acceleration rate

F017: SAFE STOP

Hits OEE: Availability

What it means: SAFE STOP was activated, or the 24 V supply failed while the drive was running (Compact PLUS units only).[1][2]

Also on: Same on VC and MC, Compact PLUS only. The related warning is A017.

Likely causes

  • SAFE STOP circuit opened
  • SAFE STOP jumper missing or checkback not connected
  • 24 V supply failure during operation

First checks, in this order

  1. Find out whether SAFE STOP was requested on purpose before you restore it
  2. Check the SAFE STOP jumper and the checkback connection
  3. Measure the 24 V supply on the Compact PLUS unit

F020: Motor temperature (VC) / Excess temperature of motor (MC)

Hits OEE: Availability

What it means: The motor temperature sensor reports a temperature above the limit, or the sensor circuit is faulty.[1][2][3]

Also on: Same number on VC and MC, names differ. On MC, P131 selects the sensor and P131 = 0 switches the fault off, which also hides real overheating.

Likely causes

  • Motor overloaded or poorly ventilated (r949 = 1)
  • Short circuit in the sensor cable or defective sensor (r949 = 2)
  • Wire break in the sensor cable or defective sensor (r949 = 4; on VC r949 = 5 means wire break and limit exceeded)

First checks, in this order

  1. Read r949 to tell overtemperature from a sensor fault
  2. Read the actual motor temperature in r009 and check load and ventilation
  3. Check the trip threshold P381
  4. Check the KTY84 sensor input -X103:29,30 (-X104:29,30 on Compact PLUS) and the sensor cable for short circuit or break

F021: Motor I2t

Hits OEE: Availability

What it means: The drive's calculated motor heating (I2t model) went above the set limit.[1][2][3]

Also on: Same number and name. On MC the monitoring switches on automatically when P383 is 100 s or more (factory setting) and P381 is above 220 degrees C; a value below 100 s in P383 switches it off. The warning before it is A029.

Likely causes

  • Motor loaded too heavily for too long by the duty cycle
  • Thermal time constant P383 or load limit P384 not set to suit the motor

First checks, in this order

  1. Check the motor load and duty cycle
  2. Check P383 against the motor data
  3. MC: also check the motor I2t load limit P384.002

F023: Inverter temperature (VC) / Excess temperature of inverter (MC)

Hits OEE: Availability

What it means: The inverter power section temperature passed its limit, or a heat sink temperature sensor is faulty.[1][2][3]

Also on: Same number, names differ. On units of 22 kW and above (the VC text says Compact PLUS) the fault can only be acknowledged after 1 minute. MC also trips when the temperature is too low (allowed ambient 0 to 45 degrees C). The warning before it is A022.

Likely causes

  • Intake or ambient air too hot, or derating not applied above 40 degrees C (45 degrees C on Compact PLUS)
  • Fan -E1 stopped, not connected or turning the wrong way
  • Air inlet or outlet openings blocked
  • VC: temperature sensor or sensor cable faulty

First checks, in this order

  1. Measure the intake air and ambient temperature
  2. Check that the fan runs in the right direction and clear the air paths
  3. Read r949: on VC 1 = overtemperature and 2, 18, 34 or 50 = wire break on sensor 1, 2, 3 or 4; on MC r949 holds the temperature at the trip
  4. VC: check the temperature sensor at -X30; r833 shows the converter temperature

F025: UCE upper switch / UCE Ph. L1

Hits OEE: Availability

What it means: The power transistor voltage monitoring (UCE) tripped in phase L1, or on Compact PLUS units in the upper switch.[1][2][3]

Also on: VC 2006 and MC call it UCE upper switch on Compact PLUS and UCE Phase L1 on other units; the 2001 VC manual calls it UCE Ph. L1. The MC first check is a ground fault at the converter outputs.

Likely causes

  • Short circuit or ground fault on output phase U2 (-X2:U2), including the motor
  • CU control board not correctly inserted
  • SAFE STOP switch X9/5-6 open on units with order numbers ending -11, -21, -31 or -61

First checks, in this order

  1. Disconnect the motor and check phase U2, the motor cable and the motor for short circuit and ground fault
  2. Check that the CU board is seated correctly
  3. Check the SAFE STOP switch X9/5-6 on units that have it

F026: UCE lower switch / UCE Ph. L2

Hits OEE: Availability

What it means: The power transistor voltage monitoring (UCE) tripped in phase L2, or on Compact PLUS units in the lower switch.[1][2][3]

Also on: Same split as F025: UCE lower switch on Compact PLUS, UCE Phase L2 on Compact and chassis units, on both VC and MC.

Likely causes

  • Short circuit or ground fault on output phase V2 (-X2:V2), including the motor
  • CU control board not correctly inserted
  • SAFE STOP switch X9/5-6 open on units with order numbers ending -11, -21, -31 or -61

First checks, in this order

  1. Disconnect the motor and check phase V2, the motor cable and the motor for short circuit and ground fault
  2. Check that the CU board is seated correctly
  3. Check the SAFE STOP switch X9/5-6 on units that have it

F027: Fault pulse resistor / UCE Ph. L3

Hits OEE: Availability

What it means: On Compact PLUS units this reports a pulse resistor (braking resistor) fault; on Compact and chassis units the UCE monitoring tripped in phase L3.[1][2][3]

Also on: VC names it Fault pulse resistor (Compact PLUS) / UCE Ph. L3; MC names it Pulse resistor fault (Compact PLUS AC/AC units) / UCE Phase L3 (chassis units). The 2001 VC manual calls it UCE Ph. L3 only.

Likely causes

  • Compact PLUS: fault in the pulse resistor circuit
  • Other units: short circuit or ground fault on output phase W2 (-X2:W2), including the motor
  • CU control board not correctly inserted
  • SAFE STOP switch X9/5-6 open on units with that option

First checks, in this order

  1. Check the unit type first: Compact PLUS means the pulse resistor message, other units mean phase L3
  2. Check the converter outputs, motor cable and motor for ground fault and short circuit
  3. Compact PLUS: check the pulse resistor and its wiring
  4. Check the CU seating and the SAFE STOP switch X9/5-6

F028: Supply phase

Hits OEE: Availability

What it means: The frequency and size of the ripple on the DC link show that one supply phase has failed.[1][3]

Also on: VC only; not in the MC fault list.

Likely causes

  • Single-phase power failure, one supply phase missing

First checks, in this order

  1. Measure the supply voltage between all three phases at the drive input
  2. Remember that a missing phase at full load can also show up as F006 on VC

F029: Meas. value sensing

Hits OEE: Availability

What it means: The measured value sensing failed its offset adjustment, so the drive cannot trust a current or other measured value.[1][2][3]

Also on: MC lists F029 as Compact PLUS only (r949 = 65 means automatic adjustment of the analog inputs not possible). VC 2006 uses a bit-coded r949 that also covers DC link voltage and temperatures.

Likely causes

  • Fault in the current measuring system
  • Fault in the power section: a valve (power transistor) that cannot block
  • Fault on the CU control board

First checks, in this order

  1. Read r949: 1 = offset adjustment not possible in phase L1, 2 = phase L3, 3 = both
  2. VC 2006 also flags other values in r949 (bit 2 DC link voltage, bit 3 inverter temperature, bit 4 motor temperature, bit 5 and 6 analog inputs); for these the manual says replace the CU
  3. For a current phase, check the current sensing and the power section

F035: Ext. Fault 1 (VC) / External fault 1 (MC)

Hits OEE: Availability

What it means: External fault input 1 (selected in P575) went active, so a device outside the drive asked it to trip.[1][2][3]

Also on: Same on VC and MC (control word 1, bit 15). Because a low signal trips it, a broken wire looks exactly like an external fault.

Likely causes

  • A real fault in the external device wired to this input
  • Broken cable to the digital input; the input is low-active, so a low signal trips F035
  • P575 points to the wrong binector

First checks, in this order

  1. Find the device that feeds the input selected in P575 and check it for a fault
  2. Check the cable and terminal of that digital input for a break
  3. Check the P575 setting

F036: Ext. Fault 2 (VC) / External fault 2 (MC)

Hits OEE: Availability

What it means: External fault input 2 went active; it is checked from 200 ms after pre-charging is complete.[1][2]

Also on: Same on VC and MC. The fault tables print P585 (VC) and P576 (MC), but both parameter lists define P586 as the source for external fault 2.

Likely causes

  • A real fault in the external device on this input, for example an external braking unit
  • Broken cable to the digital input (a logical 0 trips the drive)
  • Source parameter P586 points to the wrong binector

First checks, in this order

  1. Check the external device on this input, for example the braking unit
  2. Check the cable and terminal of the digital input
  3. Check P586 Src No ExtFault2

F037: Analog input

Hits OEE: Availability

What it means: An analog input set to 4 to 20 mA lost its signal (wire break); r949 shows which input.[1][3]

Also on: VC only; not in the MC fault list. Analog inputs on the SCI1 slave board trip F073 to F078 instead.

Likely causes

  • Broken wire or loose terminal on the 4 to 20 mA signal
  • Input configured as 4 to 20 mA in P632 for a signal that does not deliver it

First checks, in this order

  1. Read r949 to see which analog input tripped
  2. Check the wiring at -X102:15,16 for input 1 (-X101:9,10 on Compact PLUS) or -X102:17,18 for input 2
  3. Check P632 (configuration), P634 (smoothing) and P631 (offset)

F042: Calculating time (VC) / Time slot overflow (MC)

Hits OEE: Availability

What it means: The control board ran out of computing time: at least 10 overruns of time slots T2 to T5.[1][2]

Also on: Same number, different name and remedy: VC raises the sampling time, MC lowers the pulse frequency.

Likely causes

  • Too many function blocks running in fast time slots
  • VC: sampling time P357 too short
  • MC: pulse frequency too high, or synchronization (U953.33) and positioning (U953.32) enabled at the same time

First checks, in this order

  1. Check the free computing time in r829
  2. VC: increase P357 Sampling Time
  3. MC: reduce the pulse frequency P340
  4. Move individual blocks to a slower time slot

F051: Speed encoder (VC) / Encoder fault (MC)

Hits OEE: Availability

What it means: The speed or position feedback from the tacho, encoder or resolver is faulty.[1][2]

Also on: Same number, different name: Speed encoder on VC (digital or analog tacho), Encoder fault on MC (resolver, encoder, SSI/EnDat multiturn). On MC, alarm A018 (motor encoder) or A020 (external encoder) warns first when the signal amplitude is critical.

Likely causes

  • Encoder cable damaged or interrupted, or shield not connected
  • Wrong encoder settings (VC: P130, P151, P138, P109; MC: wrong encoder type, or P149 for SSI/EnDat)
  • Encoder or tacho faulty, or a short circuit on the encoder supply
  • MC: wrong cable type; encoders and multiturn encoders need different cables

First checks, in this order

  1. MC: read r949, for example 21 = A/B track undervoltage, 22 = A/B track overvoltage, 28 = encoder supply fault, 30 to 35 = SSI/EnDat protocol faults; a hundreds digit of 1 means the external encoder
  2. Check the encoder cable and its shield
  3. VC: check P130, P151, P138 and P109; P109 x P138 must be below 19200
  4. MC: after the repair switch the power off and on, so the starting position is initialized again

F053: Tachometer dn/dt

Hits OEE: Availability

What it means: The speed encoder signal changed more than twice as fast as the limit in P215 allows, which points to a disturbed or interrupted signal.[1][3]

Also on: VC only. The related VC warning is A043 n-act jump.

Likely causes

  • Interrupted tacho or encoder cable
  • Shield not grounded at both the motor and the converter end
  • Encoder cable laid together with power cables
  • Encoder that is not on the recommended list

First checks, in this order

  1. Check the tacho cable for interruptions
  2. Ground the shield at both ends
  3. Route the encoder cable away from the power cables
  4. Only then consider changing P215 or fitting the DT1 board; P806 can switch to encoder-free operation

F054: Sensor board initialization fault (VC) / Encoder board initialization fault (MC)

Hits OEE: Availability

What it means: The encoder board (for example TSY, SBP, SBR or SBM) could not be initialized.[1][2][3]

Also on: Same number, name differs. MC has many more r949 values for SBR, SBM and slot checks.

Likely causes

  • Board code incorrect, or board not compatible
  • Same board fitted twice (MC also three times)
  • MC: board in the wrong slot or not present
  • Internal error

First checks, in this order

  1. Read r949, for example 1 = board code incorrect, 7 = board double, 60 = internal error; MC adds 30 to 32 = board slot incorrect and 40 to 42 = board not present
  2. Check the board type and slot against the configuration
  3. MC from V2.0: only the SBM2 board is supported (r949 = 5)

F065: SCom telegram failure (VC: Scom Telegram)

Hits OEE: Availability

What it means: No telegram arrived on a serial SCom (USS) interface within the telegram failure time.[1][2][3]

Also on: Same on VC and MC; terminal numbers depend on the unit type.

Likely causes

  • Serial cable or connector problem
  • The USS master stopped sending
  • Telegram failure time P704 set too short

First checks, in this order

  1. Read r949: 1 = SCom1, 2 = SCom2
  2. Check the connection at PMU -X300 and at the terminal strip (VC: CU -X100:1 to 5 and -X103; MC: X103/27,28; Compact PLUS: X100/35,36)
  3. Check P704.01 (SCom1) or P704.02 (SCom2)

F082: TB/CB telegram failure

Hits OEE: Availability

What it means: The communication board (for example the PROFIBUS CBP) or technology board received no new process data within the telegram failure time P722.[1][2]

Also on: Same on VC and MC. On PROFIBUS it usually follows alarm A083 or A084.

Likely causes

  • Bus cable broken or pulled out
  • Bus master (PLC) powered down or stopped
  • Fault on the CB or TB board

First checks, in this order

  1. Read r949: 1 = TB/CB, 2 = additional CB
  2. Check the bus cable and connector to the CB/TB
  3. Check the telegram failure time P722 (0 = no monitoring)
  4. Replace the CB or TB if the fault remains

F103: Ground fault

Hits OEE: Availability

What it means: The ground fault test run at switch-on found a ground fault or a fault in the power section.[1][3]

Also on: VC only (ground fault test P375, result in r376). Not in the MC fault list.

Likely causes

  • Ground fault in the motor or motor cable
  • Defective power valve (transistor) that is always conducting
  • In phase V: SAFE STOP switch X9/5-6 open on units with that option
  • Motor shaft turning at more than 10 % of rated speed during the test

First checks, in this order

  1. Read r949 to see which valve and phase were involved
  2. Check the motor and its cable for short circuit and ground fault
  3. If no ground fault is found, check the power section for a defective valve
  4. Note that the test is set in P375 (1 = once after the next ON, 2 = after every ON)

F255: Fault in EEPROM

Hits OEE: Availability

What it means: An error occurred in the EEPROM of the control board.[1][2][3]

Also on: Same on VC and MC.

Likely causes

  • Faulty EEPROM on the CU control board, or a one-off error that a power cycle clears

First checks, in this order

  1. Switch the unit off and on again
  2. If the fault comes back, replace the CU board (or the whole unit on Compact PLUS)

A015: External alarm 1

Warning: act before it becomes a stop

What it means: External alarm input 1 (selected in P588) is active; this is a warning, not a trip.[1][2][3]

Also on: Same on VC and MC. A016 External alarm 2 works the same way with P589.

Likely causes

  • Warning from the external device wired to this input
  • Broken cable to the digital input
  • P588 points to the wrong binector

First checks, in this order

  1. Check the external device on this input
  2. Check the cable to the digital input
  3. Check P588 Src No Ext Warn1

A017: Safe Stop alarm active

Warning: act before it becomes a stop

What it means: SAFE STOP is active, so the inverter pulses are blocked and the drive will not start.[1][2][3]

Also on: The 2001 VC manual calls it SAFE OFF alarm active. MC refers to F017 for causes and remedies.

Likely causes

  • The SAFE STOP switch on X9 terminals 5-6 is open (units with order numbers ending -11, -21, -31 or -61)
  • MC: SAFE STOP detected while the drive is in a READY state

First checks, in this order

  1. Find out why the SAFE STOP circuit is open before closing it
  2. Close X9 5-6 to release the inverter pulses
  3. On Compact PLUS units use the F017 checks: jumper, checkback, 24 V supply

A018: Encoder adjustment

Warning: act before it becomes a stop

What it means: The resolver or encoder signal amplitude is in the critical range, an early warning before F051.[2]

Also on: MC only. VC has no A018.

Likely causes

  • Encoder cable or shield problem
  • Encoder getting faulty
  • In the Ready state (r001 = 009): CD track signal too small or interrupted, or an encoder without CD track with P130 set wrongly

First checks, in this order

  1. Run the F051 checks: cable, shield, encoder, correct cable type
  2. If the encoder has no CD track, set P130 correctly
  3. After the fix, switch the power off and on so the starting position is initialized again

A020: Overcurrent (VC); Encoder adjustment, external encoder (MC)

Warning: act before it becomes a stop

What it means: On VC an overcurrent condition occurred; on MC the external encoder signal amplitude is in the critical range.[1][2]

Also on: Same number, completely different meaning on VC and MC.

Likely causes

  • VC: driven load overloaded
  • VC: motor and converter not matched, or dynamic demands too high
  • MC: weak signal from the external encoder (see F051)

First checks, in this order

  1. First confirm whether the drive runs VC or MC firmware
  2. VC: check the load for overload, the motor and converter match, and the ramps
  3. MC: run the F051 encoder checks on the external encoder, then switch the power off and on

A021: Overvoltage (VC); Encoder data of external multiturn encoder faulty (MC)

Warning: act before it becomes a stop

What it means: On VC this warns of DC link overvoltage; on MC the serial protocol from an external SSI or EnDat multiturn encoder is faulty.[1][2]

Also on: Same number, completely different meaning on VC and MC.

Likely causes

  • VC: supply voltage too high
  • VC: motor regenerating with no way to feed the energy back
  • MC: protocol error from the external multiturn encoder (see F051)

First checks, in this order

  1. First confirm whether the drive runs VC or MC firmware
  2. VC: check the supply voltage and the braking path (see F006)
  3. MC: check the external encoder cable, shield and P149, then switch the power off and on

A022: Inverter temperature

Warning: act before it becomes a stop

What it means: The inverter temperature passed the alarm threshold, below the F023 trip limit.[1][2][3]

Also on: Same on VC and MC.

Likely causes

  • Intake air or ambient temperature too high
  • Fan not running
  • Air inlet or outlet openings blocked

First checks, in this order

  1. Measure intake and ambient temperature and apply derating above 40 degrees C (45 degrees C on Compact PLUS)
  2. Check that the fan runs (VC: fan -E1 connected and turning the right way)
  3. Clear the air openings; on VC read r833 for the converter temperature and check the sensor at -X30

A023: Motor temperature

Warning: act before it becomes a stop

What it means: The motor temperature passed the alarm threshold set in P380.[1][2][3]

Also on: Same on VC and MC; the matching trip is F020.

Likely causes

  • Motor overloaded
  • Poor motor ventilation
  • VC: short circuit at the KTY84 sensor input

First checks, in this order

  1. Read the motor temperature in r009
  2. Check the motor load and ventilation
  3. VC: check the KTY84 input -X103:29,30 (-X104:29,30 on Compact PLUS) for short circuit

A025: I2t Inverter (VC) / I2t converter (MC)

Warning: act before it becomes a stop

What it means: If the present load continues, the inverter will be thermally overloaded.[1][2][3]

Also on: Same number, name differs. MC lowers the maximum current limit (P129) while this alarm is active.

Likely causes

  • Converter load too high for its rating
  • VC: rated drive current P072, order number P070 or current limit P128 set wrongly

First checks, in this order

  1. Check the drive utilization in r010
  2. Reduce the converter load
  3. VC: check P072, P070 and P128

A029: I2t motor

Warning: act before it becomes a stop

What it means: The motor I2t monitoring limit was exceeded, so the motor duty cycle is too heavy.[1][2][3]

Also on: Same on VC and MC; the matching trip is F021.

Likely causes

  • Motor load cycle exceeded
  • Motor cooling, time constant or load limit parameters not set to suit the motor

First checks, in this order

  1. Check the motor load cycle
  2. Check P382 Motor Cooling, P383 and P384 Mot Load Limits

A033: Overspeed

Warning: act before it becomes a stop

What it means: The actual speed went above the positive or negative maximum speed (VC: plus the hysteresis in P804).[1][2][3]

Also on: Same on VC and MC.

Likely causes

  • Regenerative load driving the motor faster
  • Maximum speed set lower than the process needs

First checks, in this order

  1. VC: check P452 (forward maximum), P453 (reverse maximum) and P804 (hysteresis)
  2. Reduce the regenerative load
  3. Raise the maximum speed only if the machine is rated for it

A034: Setpoint/actual value deviation

Warning: act before it becomes a stop

What it means: The gap between setpoint and actual value stayed above the allowed value for longer than the monitoring time.[1][2][3]

Also on: Same on VC and MC.

Likely causes

  • Torque demand too high, for example a jammed or overloaded machine
  • Motor too small for the load

First checks, in this order

  1. Check the machine for overload or jamming
  2. Check the motor sizing
  3. Adjust P792 (allowed deviation) and P794 (deviation time) only if the process allows it

A042: Motor stall/lock (VC) / Motor stall/block (MC)

Warning: act before it becomes a stop

What it means: The motor is stalled or blocked; this is the warning that goes with fault F015.[1][2][3]

Also on: Same number on VC and MC, names differ slightly.

Likely causes

  • Drive blocked mechanically
  • Drive stalled
  • VC with speed control: encoder cable interrupted or shield not connected

First checks, in this order

  1. Check whether the drive is blocked or stalled
  2. VC: check the encoder cable and its shield
  3. Note that the alarm delay is set by P794, not by P805

A084: CB alarm

Warning: act before it becomes a stop

What it means: Telegram traffic between the PROFIBUS DP master and the first CBP board has stopped.[1][2]

Also on: Same on VC and MC for the first CBP; other CB or TB boards are described in their own manuals. A092 is the same alarm for the second CB board.

Likely causes

  • Bus cable broken or pulled out
  • DP master (PLC) powered down or stopped

First checks, in this order

  1. Check the bus cable and connectors
  2. Check that the DP master is running
  3. Note that if P722 is not 0 the drive trips with F082

Log it, or the same alarm comes back

A fault (F) trips the drive and stops the motor, so in OEE terms it is a breakdown. An alarm (A) warns first: the drive keeps running, but the same cause often becomes a fault later. Log both: faults with the minutes lost, alarms as early warnings.

  • Reason code: the code plus the drive, for example MASTERDRIVES F006, winder 2, so an overvoltage that trips on every fast stop shows up as a pattern.
  • 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.

MASTERDRIVES has been succeeded by the SINAMICS family, and fabrico.io covers SINAMICS faults in its SINAMICS 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

How do I reset a fault on a Siemens MASTERDRIVES drive?

Fix the cause, then press the P key on the PMU while the fault is displayed, or the Reset key on the OP1S (enabled through P565). A PLC or terminal can acknowledge with a rising edge on control word 1 bit 7 from the sources set in P565, P566 and P567, and the PMU always works as well. A fault that is not reset is still there after the electronics supply is switched off and on.

How do I read the fault history on a MASTERDRIVES?

r947 holds the last 8 trips, up to 8 faults each: indices 1 to 8 are the latest trip and 57 to 64 the oldest. r949 holds the fault value for each entry in the same index, and r782 the time from the operating hours counter. While a fault is displayed, hold P and press the raise key to reach the parameter level; P952 = 0 clears the whole memory.

Are MASTERDRIVES VC and MC fault codes the same?

The core numbers match (F001, F002, F006, F008, F011, F023, F025 to F027, F035, F051, F255), but names and remedies differ. Some alarms are completely different: A020 and A021 mean overcurrent and overvoltage on VC but encoder alarms on MC. F012, F028, F037, F053 and F103 are in the VC list only.

What do F025, F026 and F027 mean?

On Compact and chassis units they are UCE trips (power transistor voltage monitoring) in phase L1, L2 or L3. The manual's first checks are a short circuit or ground fault on that output phase including the motor, a CU board that is not seated correctly, and an open SAFE STOP switch X9/5-6. On Compact PLUS units the names change: F025 is the upper switch, F026 the lower switch and F027 a pulse resistor fault.

Why does my MASTERDRIVES trip with F006 when it stops?

During braking the motor feeds energy back and the DC link voltage rises past the trip threshold (about 820 V on 380 to 480 V VC units, 819 V rated on MC). Lengthen the deceleration time P464, enable the DC bus voltage controller P515 on VC, or add a way to get rid of the braking energy. Wait at least 5 minutes after switching off before opening the unit.

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. Siemens SIMOVERT MASTERDRIVES Vector Control Compendium, Edition AI, order no. 6SE7087-6QX60 (Faults and Alarms chapter dated 06.2006, Version AI; PMU/OP1S chapter 10.2004)
  2. Siemens SIMOVERT MASTERDRIVES Motion Control Compendium, Edition AN, order no. 6SE7087-6QX70 (Faults and Alarms chapter dated 03.2010, Version AL)
  3. Siemens MASTERDRIVES Vector Control Compendium, Faults and Alarms chapter, 10.2001 (6SE7087-6QX60 Version AE), copy published by MAV (Hungarian State Railways) in a procurement file
  4. Siemens SIMOVERT MASTER DRIVES Operating Instructions Part 2, Vector Control, Edition AA 08.96, order no. 6SE7087-6XX20, software V1.3 (copy hosted by MRO Electric)

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.

Book a Fabrico demo
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Related: Siemens MICROMASTER 440 fault codes · VFD drive troubleshooting · electric motor · conveyor

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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