Understanding trip codes is an important part of keeping your equipment running smoothly.  Below are some of the more common codes you may come across:

Trip CodeConditionPossible Cause
UUDC Bus under voltageLow AC Supply Voltage
Low DC Bus voltage when supplied by an external DC power supply
OUDC Bus over voltageDeceleration rate set too fast for the inertia of the machine
Mechanical load driving the motor
OI.AC**Drive output instantaneous over currentInsufficient ramp times
Phase to phase or phase to ground short circuit on the drives output
Drive requires autotuning to the motor
Motor or motor connections changed, re-autotune drive to motor
OI.br**Braking Resistor instantaneous over currentExcessive current in braking resistor
Braking resistor value to small
O.SPdOver SpeedExcessive motor speed (typically caused by a mechanical load driving the motor
tunEAutotune stopped before completionRun command removed before autotune compelte
It.brI2t on Braking ResistorExcessive braking resistor energy
lt.ACl2t on drive output currentExcessive Mechanical load
High impedance phase to phase or phase to ground short circuit at drive output
Drive requires re-autotuning to motor
O.ht1IGBT over heat based on dries thermal modelOver heat software thermal module
O.ht2Over heat based on drives heatsinkHeatsink temperature exceeds maximum allowable
thMotor thermistor tripExcessive motor temperature
O.Ld1*User +24v or digital output overloadExcessive load or short circuit on +24v output
cL1Analogue input 1 current mode, current lossInput current less than 3mA when 4-20 or 20-4mA modes selected
SCLSerial communication loss time-outLoss of communication when drive is under remote control
EEFInternal Drive EEPROM tripPossible loss of parameter values
PHInput phase imbalance or input phase lossOne of the input phases has become disconnected from the drive (applies to 200/400v three phase drives only, not dual rated drives.
rSFailure to measure motors stator resistanceMotor too small for drive
Motor cable disconnected during measurement
C.ErrSmartStick data errorBad connection or memory corrupt within SmartStick
C.dAtSmartStick data does not existNew/empty SmartStick being read
C.AccSmartStick read/write error failBad connection or faulty SmartStick
C.rtgSmartStick/drive rating changeAlready programmed SmartStick read by a drive of a different rating
O.cLOverload on current loop inputInput current exceeds 25mA
HFxx tripHardware faultsInternal drive hardware fault

* The Enable/Reset terminal will not reset an O.Ld1  trip. Use the Stop/Reset key

**These trips cannot be reset for 10 seconds after they occur

If you have an AC / DC drive module breakdown or stability issue our engineers are able to analyse the whole machine to identify where the control issues lie. Our extensive experience in retrofit and new projects means we have the knowledge to look deep into the control system where we commonly find the peripheral devices are faulty rather than the drive module.

Telephone support

Where appropriate we are often able to offer technical support by phone, we will need the following information from you:

  • Your official Purchase order (this must be received prior to any support).
  • Details of the Drive.
  • Error Codes.
  • We may also need copies of drawings and software to aid diagnosis.

Telephone support rates are £100.00 per hour, with a minimum charge of 1 hour.

Our team of engineers are also able to offer on site service and breakdown support throughout the UK to get you up and running again quickly, please enquire for details.


If you have a faulty drive but don't require on site support, Drives and Automation are able to repair them. Trained engineers will strip down your drive, assess what is required and we will then send you a repair quotation. If you are happy to proceed they will repair the drive, clean it and load test it before returning it to you. Fast turnarounds are usually no problem!

Get your faulty Commander SK repaired


The Commander SK is now a superceded product and is in it's maintenance period. Volume production of these products has now ceased, but manufacturer contractual obligations regarding warranty, service and repairs will continue. The maintenance period is expected to last up to ten years subject to raw material and component availability and will end in 2027 when no further manufacturer support will be available.  Drives and Automation are able to supply refurbished units for certain models, simply contact us with details of your existing Commander SK and we will see if we can offer you a replacement.

Call us now on 0845 3704660 to enquire about a refurbished Commander SK


In 2013, the Unidrive SP and Commander SK were replaced by a new range of industrial AC drives called Unidrive M. Unidrive M’s design is based on the success and popularity of Unidrive SP and Commander SK, and incorporates market-leading technologies.  If you are wanting to upgrade your obsolete Commander SK to an M Series Drive, use our quick reference guide to choose the right replacement Drive for your application:

Upgrade to Unidrive M from Commander SK