Jump to content
Genetry Solar Forums

Adding inductance to transformer primary


Recommended Posts

2020 48V 15KW PowerJack.  

I have some ferrite e-cores to play with, and I'm trying to get the idle current to drop a bit.  Currently, there is one OEM choke on the primary, and from that choke it splits to connect both mainboards. Would it be better to install 1 additional choke for each mainboard (adding 2 more chokes)? Or both boards combined in a single additional choke, in the fashion of the OEM PJ choke?

I wonder if each board having it's own additional choke in series would provide for some isolation between the two?  any benefit here? Is there any concern of causing the 2 mainboards to be (more) imbalanced?


Option 1:                                       PJ A1-----------(new L)-------+====(PJ L)====xfmr

                                                      PJ B1-----------(new L)-------+


Option 2:                                       PJ A1-----------+===(new L)===(PJ L)=====xfmr

                                                      PJ B1-----------+


Forgive my ASCII art, I cannot get an image to upload/attach to this post. 


Link to comment
Share on other sites

As long as the ferrite combinations are balanced between the 2 mainboards, you should be just fine.  Definitely would not recommend imbalanced ferrites between the 2 mainboards.  Both mainboards are driven with exactly the same drive signals (as in, same connection points, not separate outputs).

The stock PJ ferrite is pretty good...IF it has 2 full turns of wire around it.  In my experimentation, it's roughly the same as an E-core (have experimented with those as well).

The ferrite is basically absorbing/filtering the 24KHz SPWM carrier from the FETs.  The main transformer will have an extremely low impedance at 24KHz, causing extremely high no-load current due to the transformer deadshorting the FETs.  The more of this "carrier" that is absorbed by the ferrites, the better the no-load current will be.  The lower limit of the no-load current is the main transformer's magnetizing current + switching losses / control circuitry power requirements; it is not possible to reduce the no-load current farther than this with ferrites.

Link to comment
Share on other sites

Thanks, Sid, that's what I was thinking. I tried the E-Cores in both configurations; both produced favorable results, but the idle consumption was a tad bit lower with 2 separate chokes.  I was able to get it down to 46W at idle (down from ~110W originally).  

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...