This is in general, when speaking of the output current of a 3 phases inverter we are speaking of one line current or of the sum of three lines currents? Or other?
Example we have a three phase load (motor) in star connection. Let's say no neutral connected.
The switching stage produces three voltage outputs that generate three different currents on the three motor inductances.
The three currents have the same rms (balanced load of course) but they are three. So the source, the rectifier 3 phase or 1 phase input must be able to supply three times the current of one line. Is this correct?

 

JeffersonAirplane
Welcome to Control.com!
The source must have as many lines as the load! That is 3 for 3-ph motor.
Regards, Phil Corso

 

Yes JeffersonAirplane the source can have a different number of lines than the load, small inverters with 1 phase in and 3 phase out, eg 230V single phase in 230V three phase out.
Inverters are generally variable voltage and frequency so at low loads, when output voltage is well below line voltage, you can see a higher output current than line current. There are efficiency losses as well so the line current will be higher than the output current when at high load. At high load, 3 phase in 3 phase out inverter, line current would approximately be output current / inverter efficiency. For 1 phase in 3 phase out inverter, the line current would approximately be root 3 x 1 phase out current / inverter efficiency.

 

My question is more like this : when it is said that current output is of example 99 amp this means that, in case of 3 phase output, in each line current is 99 amp or 33 amp (99/3)?

 

In this example each line current would be 99 / inverter efficiency. Typical efficiency is 98% (0.98), so around 101 amps. This is at high/full load when line and output voltage are almost the same.

 

A three-phase inverter's output current varies with the load. If it is wired to an alternating current (AC) motor, for instance, the current will change based on the load on the motor. The output current of a three-phase inverter is typically the additive total of the currents flowing through its three output phases.

 

The output current of a three-phase inverter is typically the additive total of the currents flowing through its three output phases.

The output current of a three-phase inverter is the current flowing through one phase. The output power of an inverter is:
V * I * root 3 * power factor

 

My question is more like this : when it is said that current output is of example 99 amp this means that, in case of 3 phase output, in each line current is 99 amp or 33 amp (99/3)?

Jefferson,

When it is said that current output is 99 amps, it is line current. If you had a clamp meter (true rms) on one wire from VFD to motor that should measure 99 Amps.