Three Phase 2 Level PFC inductor design

Status
Not open for further replies.
C

chaitanyab

Member level 3
Joined
Dec 8, 2009
Messages
67
Helped
3
Reputation
6
Reaction score
3
Trophy points
1,288
Location
Pune
Activity points
1,878
Hi,

I am looking for an Appnote or reference for three phase 2 level boost PFC inductor design. The Basic 6 switch boost PFC. Surprisingly I am not able to find any reference on the internet. Any pointers will be appreciated.

Thanks
 

Sort by date Sort by votes
I don't see any reason why inductor design approach would be different for a three phase vs single phase boost PFC. Unless you want to do something strange like use a common core for the three inductors....
 

    C

    chaitanyab

    Points: 2
    Helpful Answer Positive Rating
Upvote 0 Downvote
3 triangle waves 120 deg apart ( say 20kHz ), a sine wave ref for each of the 3 phases, phase locked to the P-N voltage at input for each phase - some current limiting and decent gate drive and away you go -

an error amp running off the Vout ( DC ) to modulate the 3 sine wave refs above - and job done

- et Voila ... ! easy peasy ...
 

Upvote 0 Downvote
It's possible to have one common core for 3 inductors...
by staggering action at mutually exclusive times. My simulation turns on each switch at 20 percent duty cycle. It's enough time for 22mH to rise to 7 Amperes. At turn-Off the diodes conduct briefly, just before a neighboring coil turns On.

By 2 levels do you mean you want positive and negative outputs? If so then it requires a contrived gating scheme.

 

Upvote 0 Downvote
If you have 3 phase...you can just use a 6 pulse diode bridge.....and that gives you good enough PFC....as long as you keep the output cap of the bridge low enough.
 

Upvote 0 Downvote
Following Circuit is what I am looking for to design, especially the inductors:


Now as per mtwieg suggestion I have decided to use the single stage PFC inductor equations (which are abundantly available on internet / text book references)
Now normally three phase PFC is used for high power. In my case 10-20kw. 3 ph 415Vrms, 50Hz/60Hz input, probably give me 600VDC PFC output.
So I am thinking it will be CCM only. So in theory Single stage PFC design in CCM mode, use for 3 inductors should work is my understanding.

mtwieg and others please comment.
 

Upvote 0 Downvote
Even for just 6kW, a totem pole PFC which splits the single phase to 3 phases is used as in attached
...so it will be very demanding to do it with that cct in post #6.....what you show is , or appears to purport to be , a bridgeless 3 phase PFC......and i dont see the low frequency switch branch's for your phases.
I think #6 cct needs verification.
 

Upvote 0 Downvote
I think the circuit is correct, it does not need low frequency branch. It operates as described in post #3 ( three phase carrier locked to input voltage phase creating 3 phase PWM) unlike the totem pole which you have mentioned in the link which kind of operates with one phase and neutral and then all 3 put together.
 

Upvote 0 Downvote
I confirm that post #6 PFC circuit is industry standard, except for a missing LC filter that blocks PWM frequent currents. Also a DC bus precharge circuit in parallel to the mains contactor is required. I agree that the chokes can be basically analyzed as single phase chokes.

Similar to motor inverter, the PFC will use symmetrized modulation (superimposed 3*f0 zero sequence) to reduce the minimal DC bus voltage.
 

    C

    chaitanyab

    Points: 2
    Helpful Answer Positive Rating
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…