Inverter Duty Motor

[HamidEle]

If we specify inverter duty motor, do we sill need line reactor /filter on VFD output provided voltage spike does not exceed NEMA-MG- 31 limit?

I tend to be more cautious about this. Normally I ask for the load recator as a minimum requirements. Because most LV motors are designed for inverter duty as well.
If the added costs for load reactor-filter are not that high, I would add them for most of application.

Any inputs would be appreciated.

 

[DickDV]

It's not possible to answer your question responsibly without knowing the motor hp, the power supply voltage, and the length of the motor leads.

As to adding a reactor in the motor leads, they are inexpensive filters to buy but they also drop voltage. In fact, a 5% reactor will drop 5% of its source side voltage when operating at nameplate current. Before buying that reactor, you should check to see if you have enough voltage for the motor at full load and full speed.

 

[MAGTiger]

The voltage the reactor drops is reactive (Vx) and subtracts vectorially from the supplied voltage. So while you will measure 5% voltage across the reactor's coil in to coil out terminals the line to line output terminals voltage will be greater than 95% of the input terminals. All this assuming your meterinc can resolve the distortion into the correct Vrms values.
As far as needing additional filtering or reactor in this application, it depends on other factors, like cable length and type as well as how critical the process is. A reactor or dv/dt filter can be cheal insurance for a mission critical application.

Neil