Accueil > Commissioning tips > Commissioning ATV31 variable speed drive – Protection, monitoring, self-tuning and resolution of the Nst fault
Commissioning tips

Commissioning ATV31 variable speed drive – Protection, monitoring, self-tuning and resolution of the Nst fault

Protect the motor

Set the thermal protection of the drive to protect the motor. On the motor nameplate, store the nominal current and report it to the Ith parameter of the drive

SET menu Ith = I motor name

Optimization or auto-tuning or Tuning of the drive / motor assembly

This operation is not essential but it is strongly recommended, it allows, among other things, to optimize the currents (reduce them) which avoids overheating and allows energy savings.

In practice, it is a matter of reading the information from the motor nameplate and copying it to the drive, then launching Tun or autotuning

The motor must be connected to the drive (downstream contactor active) and the LI1 or LI2 run command must be deactivated.

Menu drC 

UnS = rated motor voltage

FrS = Rated motor frequency

nCr = Rated motor current rating

nSP = rated slip motor plating

COS = motor cosine phi plated motor

tUn = YES : validate with the ENT key for at least 2 sec. If the autotuning operation went well, tUn changes to Done (done)

To monitor engine temperature

ATV31 frequency converters do not have the motor thermal monitoring function via PTC probes. It is nevertheless possible to easily perform this function via a module dedicated to this monitoring.

This is the control device for thermal protection with PTC thermistors: LT3S range

Precautions to be taken for connection concerning probes:

• check if the motor probes are PTC technology and not PT100 – the LT3S only works with PTC probes,

• check whether the motor has 3 probes in series distributed in the motor and with a total value of 750 ohms at 20 ° C,

• if the motor has only one resistance probes (surface probe), the probes of 3 motors can then be put in series and connected to a single LT3S.

To resolve the Nst fault on power-up

Nst can be:

  • a drive status: Waiting for a command by bus or communication network (CanOpen, Modbus,, TCP / IP, ..). the drive is then wired. If you want to test the drive out of communication, for example with the terminal block or the display, un-wire the drive and force it to factory settings
  • a fault if the drive is not wired to a network or a bus.

The tCt [2-wire control type] parameter is set to the trn [Transition] value in the factory setting, this setting indicates that a transition or edge state change is required to start operation in order to avoid an untimely restart after a power interruption. This configuration can cause NST faults when the power is turned back on, to avoid:

  • Check that the product is in 2-wire control, position it in this configuration: I-O menu tCC = 2C
  • all you have to do is set the tCt [2-wire control type] parameter to the LEL value [Level] (state 0 or 1 is taken into account for running or stopping):

Menu I-O  tCt = LeL

Please note, the product restarts when the power is turned on; check if the safety of goods and people is taken into account

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