During the classes of "electric drives" this 2-level inverter was drawn:


I have searched online and tried to understand from book how it works, but I still have some basic (and probably stupid) doubts.

1) I understood that: the input on the left is 3-phase signal (120 phase shift), after the rectifier only the "peaks" of the 3 input sine waves remain, then the capacitor filters and, thanks to the PWM on the gates of the mosfets, the mosfets produce PWM square waves in output (on the right).
Is this correct so far ??
(it's very rough, but it's for understanding).

Take the case of an inverter of an electric car.
2) The inverter converts DC to AC ... but where is the DC battery in the picture? I only see one AC input and one AC output in the picture ...

3) The PWM signals generated by the microcontroller are "connected" to the gate of the transistors, right ??

4) Are the diodes between drain and source of the mosfets used to make the inverter bidirectional ?? ..sending back to the DC supply the power from right to left

Thank you for your patience

 

1)
Everything to the right of the 3-Phase-Bridge-Rectifier is DC.

2)
If a Battery is used to supply Power, there will be no need for the Rectifier.

3)
What You are looking at is a Generic-Block-Diagram, showing general necessary functions,
not a comprehensive Schematic-Diagram of a real functioning device.

4)
No,
These Diodes are not separate Components "added-in" to the Circuit.
These Diodes are part of the basic physical structure of the FETs,
and are contained in all standard N-Channel, and P-Channel, Enhancement-Mode FET-Transistors.
Sometimes these "Intrinsic-Diodes" are useful and convenient, but generally they have
poor performance when compared to separate custom-specified, High-Speed-Diodes.
.
.
.

 

1)
Everything to the right of the 3-Phase-Bridge-Rectifier is DC.

2)
If a Battery is used to supply Power, there will be no need for the Rectifier.

3)
What You are looking at is a Generic-Block-Diagram, showing general necessary functions,
not a comprehensive Schematic-Diagram of a real functioning device.

4)
No,
These Diodes are not separate Components "added-in" to the Circuit.
These Diodes are part of the basic physical structure of the FETs,
and are contained in all standard N-Channel, and P-Channel, Enhancement-Mode FET-Transistors.
Sometimes these "Intrinsic-Diodes" are useful and convenient, but generally they have
poor performance when compared to separate custom-specified, High-Speed-Diodes.
.
.
.

Thanks for the detailed answer.

I still haven't figured out question 3, i.e. whether the PWM control signals are at the gates of the mosfets (assuming the inverter of an electric car)

 

I don't understand,
of course the PWM-Signal has to control the FET-Gates,
otherwise nothing would happen.

The Inverter of an Electric-Car is highly-refined, and specialized,
and much more complex than the Block-Diagram would lead You to believe.

There's nothing simple about an EV-Inverter, it's patented, and kept secret, in almost every case.
.
.
.

 

I don't understand,
of course the PWM-Signal has to control the FET-Gates,
otherwise nothing would happen.

The Inverter of an Electric-Car is highly-refined, and specialized,
and much more complex than the Block-Diagram would lead You to believe.

There's nothing simple about an EV-Inverter, it's patented, and kept secret, in almost every case.
.
.
.

LQC is correct, except that the inverter controls are vastly more complex, considering that they not only provide variable speed but also variable torque, as well as regenerative braking to send power back to the battery as the car slows.