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Registered Member #1773
Joined: Tue Oct 21 2008, 06:56PM
Location: Poland
Posts: 93
Good Day Josh Campbell !
I have a few questions for you. Why do you don't use DC blocking cap on out fullbridge? Why use two different types of ferrite cores? What will change increase / decrease the working coil diameter of the pipe? I know it will change the inductance and fo. The smaller diameter of the pipe is greater resistance and losses. You currently use a pipe with a diameter of 10mm I think. Typically, when used under 10-15KW pipe with a diameter of 6mm. What benefits can result from the use of smaller diameter pipes?
Is the cooling of a capacitor is sufficient? Where you bought these capacitors? Do not heat up the housing elements?
Registered Member #5258
Joined: Sun Jun 10 2012, 10:15PM
Location: Missouri - USA
Posts: 119
Robert2 wrote ...
Good Day Josh Campbell !
I have a few questions for you. 1. Why do you don't use DC blocking cap on out fullbridge? 2. Why use two different types of ferrite cores? 3. What will change increase / decrease the working coil diameter of the pipe? 4. I know it will change the inductance and fo. The smaller diameter of the pipe is greater resistance and losses. You currently use a pipe with a diameter of 10mm I think. Typically, when used under 10-15KW pipe with a diameter of 6mm. What benefits can result from the use of smaller diameter pipes?
5. Is the cooling of a capacitor is sufficient? 6. Where you bought these capacitors? 7. Do not heat up the housing elements?
The second and third prototypes did not have DC blocking caps however the current version does use capacitive coupling between the bridge and matching transformer. As you know a DC blocking capacitor should behave like a short at working frequency. Calculate the reactance in ohms of the DC blocking capacitor for a minimum value at your working frequency, Xc(ohms) = 1/(2 x 3.14 x f x C). The reactance should be less than 2 ohms at working frequency, which is around 40-60Khz in my current setup. You also need to pay attention to the self resonance frequency of the capacitor and ensure that the capacitance does not react with the inductance of the primary in the matching transformer in an undesirable way.
I think what you are referring to is the old toroidal cores used in my earlier setup, I just used what I had on hand. I was saturating the core so I added more of a different type. I'm now using a large type 3C85 E core.
It will have a very small effect on inductance and f(o), the bigger issue will be cooling if you go smaller.
The current sizes I'm using on working coils are 1/4" (6.35mm) and 3/8"(9.525mm). The smaller tube offers higher turn count in a smaller area which allows for higher L, lower f(o) and concentration of those parameters in a smaller area, desirable in some setups.
In the old setup the caps got warm operating at 100% but never overheated. The new setup uses Celem water cooled caps, zero thermal issues at 100%.
The old euro-farad caps are from eBay, the new Celem are direct from Celem in Israel.
Yes actually the housing did head up in the old version a bit due to all the parasitic inductance. The new setup with the better matching transformer contains the field much better and has a very low amount of parasitic inducuance.
Here's a video and a few photos of the current setup. I'm working on getting all the specs and build details put together to make this available on this forum and on the Github project repository.
Registered Member #1773
Joined: Tue Oct 21 2008, 06:56PM
Location: Poland
Posts: 93
Thank you very much for your extensive reply. Why do not I see in you any large capacitors in the power supply of the bridge ? Have followed two large ferrite transformer . This material 3C85 , wrote that this type of E. It seems to me that I see C- cores or UI or L. What did you use the size of the core ? How many turns of the primary winding is ? What power has the final version of the photos , the core ? I am planning heater power of 15KW , I wanted to use the TX58 core 8-10 , 3E25 material
Even considering buying the core : F887 material . Considering also connected to the 4 sets of cores E80 / 38 / 20-3C90 or two sets of U93 / 76 / 30-3C90 Induction heater will operate at a frequency of ~ 80kHz . Are you able to help me choose which of the available cores that you have presented , and specify the number of sets ? The heater is working with graphite crucible
Registered Member #5258
Joined: Sun Jun 10 2012, 10:15PM
Location: Missouri - USA
Posts: 119
Robert2 wrote ...
1. Why do not I see in you any large capacitors in the power supply of the bridge? 2. Have followed two large ferrite transformer. This material 3C85 , wrote that this type of E. It seems to me that I see C- cores or UI or L. 3. What did you use the size of the core ? 4. How many turns of the primary winding is ? 5. What power has the final version of the photos , the core ? 6. I am planning heater power of 15KW 7. I wanted to use the TX58 core 8-10 , 3E25 material
There are no filter capacitors, the DC supply is unfiltered. At higher power levels this has some important benefits. (low PF, low reactive power, less RFI)
In these photos I'm still using the dual UI cores in an EI configuration. Total AL = 6800
The unit shown can run on single phase 240V drawing 90A (100A breaker) with robust cooling. I limit it in software to about 65A peek input current and find that a modest 30-35A is plenty to heat typical applications with ease and speed.
15KW of input power? Are you counting reactive power in that total?
3E25 is made for EMI suppression, although it will likely work it has a sharp drop off in permeability at about 140ºC. The Ferroxcube 3C90 material or similar is ideal for this power application.
Rough UI dimensions.
Planned core type E/I configuration. Some helpfull core calculators.
Registered Member #1773
Joined: Tue Oct 21 2008, 06:56PM
Location: Poland
Posts: 93
Thank you again for your reply. Sometimes it happens that someone does not answer. I am very grateful for your answers. I want to get the output power of 15KW, induction heater is designed for the early melting of silver in a graphite crucible. In my country, it is not possible to use a single phase power supply with such a large current. The solution is 3x380VAC three phases. I want to use the bridge rectifier, the output will be around 550VDC. 1. How do you adjust the power? You are using a thyristor or SRC to adjust? I think about the power control using the phase shift. 2. You say that you set the maximum input current of the controller. Conclude that the feedback is performed by measuring current flow bridge? Now, however, I noticed that there are two current transformers.
I intend to use high-speed IGBTs, 2MBI200NB-120 PDF Already predicted to cooling water block. The makings of a resonant capacitor WIMA FKP-1. 4,6uF Ultimately, it will be 140 pieces of capacitors, mounted on copper flat bar. They will use the fan cooling section. Capacitors Act so that they are between spacing and air can heat away
Registered Member #5258
Joined: Sun Jun 10 2012, 10:15PM
Location: Missouri - USA
Posts: 119
Ramonn wrote ...
...
parasole wrote ...
Hi Josh, any chance for updates on GitHub/ReactorForge?
Yes. You can also follow the blog for updates or posts on Patreon. I will continue to update this forum thread as well. Although at some point I might make a new thread, to separate the older models (Prototypes, MKI, II, etc.) from the new ReactorForge types.
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Induction Heater - Series Resonant - uC/PLL Tuning [ReactorForge]
