Where single-phase ac motor is better than three-phase?

[kabuto15]

Hi.
I built some voltage source inverter to supply single-phase motor. I met some person, who told me that using single-phase induction motor with inverter have got no sense, because it isn't economical. Ok, I said. Now, I want to prove this guy that in some special applications using single-phase is better than three-phase. Maybe, you know some applications where using single-phase+inverter is better than three-phase+inverter ?

 

[FvM]

What's exactly a single phase motor in your opinion? A motor must have a rotating field at least to produce a starting torque.
So "single phase" only means, it can be connected to a single phase grid, but internally, it utilizes phase shift. Most "single phase"
motors are either two-phase (capacitor) motors or split pole (split phase) motors.

 

[kabuto15]

Somethink like PSC and control like in reference sheet
https://ww1.microchip.com/downloads/en/AppNotes/00967A.pdf

 

[rushirajdhar]

are i think it matters with how much load on your motor.........then decide whether go to single phase or three phase....but for three phase circuitry will be more complex than single..
MOD: Hope there is no need for bold letters

 

[kabuto15]

Simple V/f control is only a little more complex for three-phase. The main disadvantages of single-phase motor: it hasn't starting torque, need capacitor (PSC), it's bigger, small efficiency. But in some abstracts I find the new methods of controls for single-phase (like IRFOC with speed estimation !, ISFOC https://hal.archives-ouvertes.fr/docs/00/43/34/90/PDF/Boussak_tpel_final.pdf). Why some scientists try to develop new methods ?

 

[FvM]

As expectable, the mentioned literature doesn't say a word about a "single phase" motor being better in VFD applications
any way. The only motivation for these designs is the obvious fact , that the motor type is very common and it doesn't pay
in some cases to redesign an existing motor.

Because the presented circuits are full three-phase bridges, the electronic part count isn't different from a standard three-phase
motor drive. But due to the unsymmetrical currents, the ultilization is worse, you also have higher bus ripple current and a pulsating
torque and possibly higher control effort.

Apart from this, I keep my opinion, that these motors should be better designated two-phase motors according to their construction.