Designing an Interstage Transformer
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
 3rd March 2013, 03:20 AM #21 TheGimp   diyAudio Member     Join Date: Aug 2009 Location: Johnson City, TN After doing more research I found this paper: http://www.intalek.com/Index/Project...rmeability.PDF Figure 1.17a on page 3 shows permeability peaking about at the middle of the BH curve slope. I measured the current and voltage through the secondary with an adjustable resistor in series with the transformer. I adjusted the resistor to have a voltage drop equal to the voltage drop across the transformer, and used this to calculate the inductance. The peak inductance should coincide with the peak permeability. No? If so, then the peak permeability occurs with an input voltage of 11.3V with a current of 78mA for an inductance of 0.477H. From this and the number of turns I can calculate Mu. Is this the proper point at which to calculate Mu? Or does this only tell me the peak flux density at saturation?
iko
diyAudio Moderator

Join Date: May 2008
Location: Toronto
What's the window area? As defined by D x F in the attached image.

It so happens that I've become interested in winding my own inductors too, but won't start with an interstage transformer. Will probably do filter chokes first. We could exchange notes if you'd like.
Attached Images
 niei.gif (8.2 KB, 572 views)

 3rd March 2013, 06:43 AM #23 iko   diyAudio Moderator     Join Date: May 2008 Location: Toronto These are the formulas I found for the design of an inductor with DC, and using these the relative permeability is not needed. N = (L*Ipk*10^4)/(Ac*Bm) where N = the number of turns L = desired inductance Ipk = peak current = Idc + Iac/2 Ac = effective core area Bm = desired max flux density, usually 1.2T Assuming Ac = 5.68 cm^2, Idc = 10mA, Iac = 4mA, L = 44H, and Bm = 1.2T, gives N = 774 turns. Next would be to evaluate the max wire size that would fit so many turns in your winding area, or window area Wa. The wire are in cm^2 is given by Aw <= Ku Wa / N Ku = window utilization factor (constant), which for laminates like you have is 0.48. Hence my question for your core Wa. Next, calculate the gap length, in cm: lg = (0.4*pi*N*N*Ac*0.00000001)/L In your case lg = 0.001198 cm, which is equivalent to just butting the ends together with not paper between them, roughly. One sheet of fish paper is about 7 mils, which is about 0.01778 cm. We should probably take into account the fringing flux Frf = 1+(lg/SQRT(Ac))*LN(2*D/lg) where D is the window height as seen in the image I attached previously. Knowing F you can recalculate the number of turns: N' = =SQRT((lg*L)/(0.4*pi*Ac*Frf*0.00000001)) There's more, I'm working on a spreadsheet too.
 3rd March 2013, 06:58 AM #24 ErikdeBest   diyAudio Member   Join Date: Mar 2003 Location: Zürich Hi theGimp and Ikoflexer! Winding own transformers is another of my long term goals, so I don't mind if you keep exchanging notes on diyaudio so I can pick up some information as well. Erik __________________ my surname is indeed 'de Best': neither misspelling nor snobbism! Ask SY!
TonyTecson
diyAudio Moderator

Join Date: May 2003
Location: Palatiw, Pasig City
Quote:
 Originally Posted by 316a Hammond 126C and 126B , to me sound superb for a £30 a piece lump of iron . These bifilar 1:1 IT are a bargain , probably the biggest bang for buck out there 316A
thanks for your input, did you try to measure frequency response? i thought that winding biffilar increases winding capacitance to affect hf?
__________________
planet10 needs your help: Let's help Ruth and Dave...http://www.diyaudio.com/forums/plane...ml#post5010547[B

sjs
diyAudio Member

Join Date: Oct 2011
Location: Manchester
Quote:
 Originally Posted by Tony thanks for your input, did you try to measure frequency response? i thought that winding biffilar increases winding capacitance to affect hf?
this may be worth a read: Audio Note Kits - Interstage Coupled Amps

 3rd March 2013, 02:59 PM #27 sjs   diyAudio Member   Join Date: Oct 2011 Location: Manchester and here are some typical FR for some bifilar ITs from back in the late 90s with -3dB beyond 120KHz http://www.sjselectroacoustics.co.uk/images/IT102.GIF and http://www.sjselectroacoustics.co.uk/images/IT103.GIF
 3rd March 2013, 04:24 PM #28 TheGimp   diyAudio Member     Join Date: Aug 2009 Location: Johnson City, TN I've been interested in winding transformers for many years but never seemed to have the time to study it sufficiently to understand what I'm doing. ikoflexer, window measurements are 1.1cm X 3.33cm for an area of 3.663 sq-cm The calculations for the 1:1 interstage transformer should be very much like those for an inductor. If Bi-Filar wound, construction is the same, except two wires are feed at the same time. Eric, this is an ope forum so every one is welcome to participate or just follow along as they wish. Tony, bi-filar does increase coupling capacitance, apparently this is not always bad. sjs, thanks for the links. I still wish to measure the characteristics of these cores so I can use those values in my calculations. So if anyone can give me some guidance I would appreciate it.
6L6
diyAudio Moderator

Join Date: Oct 2010
Quote:
 Originally Posted by TheGimp Tony, bi-filar does increase coupling capacitance, apparently this is not always bad.
Over in the Pass Labs forum we are using a 1:1 to 1:1 quadra-filar interstage transformer as an interstage transformer/phase inverter for the F6 amp, the capacitance of the windings is not an issue.

I also don't think it's avoidable, so no worries...

iko
diyAudio Moderator

Join Date: May 2008
Location: Toronto
This is what I get for your core. This calculates one winding, assuming it occupies half the total winding area. It also assumes standard industry silicon steel core and a target working Bmax of 1.2 tesla. The method used is called the area product method (temperature rise) from the book Transformer and inductor design handbook by Col. Wm. T. McLyman.
Attached Images
 itcalc1.PNG (59.1 KB, 565 views)

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Aussie Amplifiers         CSS         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post HP8903B Tubes / Valves 19 10th May 2012 05:36 AM galac Tubes / Valves 6 30th July 2011 05:54 PM NickC Tubes / Valves 4 6th January 2011 12:57 AM m6tt Tubes / Valves 3 5th January 2011 11:14 PM effindi Tubes / Valves 8 10th November 2009 01:51 PM

 New To Site? Need Help?

All times are GMT. The time now is 10:31 PM.