Author Topic: Looking for manufacturer of huge inductor  (Read 23491 times)

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Offline poorchavaTopic starter

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Looking for manufacturer of huge inductor
« on: October 30, 2014, 10:43:02 pm »
Hi,

I'm working on a high power adjustable DC-DC converter. Because of low frequency (30-60-ish kHz) I have calculated that the inductor I need would be about 150-200uH rated at 30A (ya, i know, it will be large). Do you know a manufacturer that has stuff like that available off-the-shelf? I have shecked typical suspects like Murata, Epcos/TDK, Vishay, Coilcraft, Bourns, TayoYuden and a few others, but they usually don't have anything remotely close to what I need. I'd prefer the manufacturer to be based somewhere in EU, but it's not a hard condition.

I know I can buy the core and some bigass magnet wire (or rather litz wire) and wind that myself or have such inductor suctom made by a specialized company. First solution is time consuming and the second one is expensive and involves long wait time, in addition, the final demand for the component will be about 100pcs/year tops.
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Offline GK

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Re: Looking for manufacturer of huge inductor
« Reply #1 on: October 30, 2014, 11:02:07 pm »
Quote
I know I can buy the core and some bigass magnet wire


200uH at 30A is an LI2 product of 180 millijoules. A hefty ETD59 core gapped down to an AL value of 200 will support 55 mJ. Although it's not recommended to go much lower you could gap it to support 60 mJ and put three of them wound for 67uH in series.

:P

I am currently winding an ETD59 for 100uH at 20A.

« Last Edit: October 31, 2014, 01:38:00 am by GK »
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Offline GK

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Re: Looking for manufacturer of huge inductor
« Reply #2 on: October 30, 2014, 11:24:27 pm »
I've done several ETD59's now to 50 mJ (That's still within the operating range specified by the manufacturer) and coil heating is mostly due to resistive losses.

Admittedly three ETD59's are far from practical, but the OP's options are really limited here unless he rewrites his specification.

I do not know of any off-the-shelf ferrite core that can support a whopping 180 mJ.
« Last Edit: October 30, 2014, 11:31:06 pm by GK »
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Offline GK

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Re: Looking for manufacturer of huge inductor
« Reply #3 on: October 30, 2014, 11:53:04 pm »
you can't just keep shiming the windings out.


I didn't say otherwise and I even posted the ETD selection curves provided by the manufacturer and gave an worked example within the specified limitations.

I thought it would have been obvious that I gave the ETD59 example not as a practical solution, but to give the OP some perspective for what he is asking for.
If you're worried about going all the way to 60mJ with an ETD59 you can just play it safe and put, say, five 40uH ETD59 inductors in series instead  :P
« Last Edit: October 30, 2014, 11:56:00 pm by GK »
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Offline poorchavaTopic starter

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Re: Looking for manufacturer of huge inductor
« Reply #4 on: October 31, 2014, 12:23:55 am »
A bit more on the spec:
Vin: 15-35V
Vout: 10-30V
Iout: up tp 25A
Footprint: 100mm x 150mm (more or less)

So we're looking at target output powers of up to 750W. In current hardware revision, the inductor is about 400uH wound with 2.5mm^2 magnet wire on about 50mm diameter toroidal core, presumably Material 26. Figured out it's T184-26 with Al=169nH. How this inductor was calculated - no idea, i'm redesigning a circuit made by someone else. To get this inductance with this core it's in the ballpark of 50turns, which checks out.

Anyway - the converter is purely software-controlled (PWM from uC driving the bridge). FET driver is IR2110S, which would do fine at somewhat higher frequencies. What bothers me is that I'd like to sample 4 values with ADC at precisely controlled moments to avoid switching transients, and I can hardly do that at frequencies higher than 30-40k, I'd need to average and digitally filter the results. Admiteddly I have not tested the current design at anything close to full-scale power, only about 80W (and it worked fine).

Multiphase converter is kinda out of question, as the control board is already done and there is no pins left on the microcontroller (well, at fixed frequency I could theoretically phase-shift the signals with some 7400/4000 series logic or something). It seems that increasing frequency is the only way to go.

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Offline GK

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Re: Looking for manufacturer of huge inductor
« Reply #5 on: October 31, 2014, 12:47:57 am »
A bit more on the spec:
Vin: 15-35V
Vout: 10-30V
Iout: up tp 25A
Footprint: 100mm x 150mm (more or less)

So we're looking at target output powers of up to 750W. In current hardware revision, the inductor is about 400uH wound with 2.5mm^2 magnet wire on about 50mm diameter toroidal core, presumably Material 26. Figured out it's T184-26 with Al=169nH. How this inductor was calculated - no idea, i'm redesigning a circuit made by someone else. To get this inductance with this core it's in the ballpark of 50turns, which checks out.



You should have mentioned that you are using powered iron toroids. They're a pain to wind and I couldn't find a local distributor for small quantities,  but they are much more compact than the alternatives.

However for 400uH at 25A a 2" diameter toroid seems a bit small. 3" would be better:



Go here:
http://www.micrometals.com/software.html


Your 2" toroid would likely be fine if you only need 150-200uH. I don't fancy your chances of finding an suitable pre-wound toroidial inductor off-the-shelf. I think you'll be stuck with winding your own.
 
« Last Edit: October 31, 2014, 01:46:37 am by GK »
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Offline T3sl4co1l

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Re: Looking for manufacturer of huge inductor
« Reply #6 on: October 31, 2014, 01:49:55 am »
Mind that #26 and #52 powdered irons are so lossy, they're basically only suitable for extremely low ripple applications: excessively large inductances on lowish frequency converters (30-100kHz, say, and under 10% ripple), or subsequent filtering (where the AC loss impedance doesn't hurt too much anyway).

I've seen ferrites over 3" across (EE80 or thereabouts), should be able to store a good bit of energy in those.  But really, you should consider redesigning the whole damn thing... there's a reason it's looking expensive this way..

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Offline Richard Head

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Re: Looking for manufacturer of huge inductor
« Reply #7 on: October 31, 2014, 07:09:06 am »
I agree with Tim. Micrometals 26 material (yellow-white) is only meant for 50-60Hz EMI filters. It's extremely lossy at high frequency. If you insist on using powdered iron then 90 material (yellow-red) is far better. I've used 90 material for output inductors at 100kHz many times and it's fine, as long as you limit the flux swing.
However, my first choice would be a gapped ferrite such as an E65. The operating frequency of 30-60kHz is so low that you'll be saturation limited rather than loss limited. I haven't done the calculation but suspect that you could use a single E65 easily. If using current mode control then limit the peak flux density to 270mT. If you distribute the air gap between all three legs then it shouldn't be too big.
If you don't have a lot of experiance with switchmode PSU's then I suggest you stick to the lower frequencies as it's far more forgiving.

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Offline GK

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Re: Looking for manufacturer of huge inductor
« Reply #8 on: October 31, 2014, 09:24:58 am »
Mind that #26 and #52 powdered irons are so lossy, they're basically only suitable for extremely low ripple applications: excessively large inductances on lowish frequency converters (30-100kHz, say, and under 10% ripple),



That appears to be what he has. Admittedly he has a toroid of less than suitable material (assuming it has been correctly determined), but a 2" or a 3" toroid of the correct material could do the job he wants, with significantly better shielding than, say, a big E core, which may or may not be an advantage.
« Last Edit: October 31, 2014, 09:47:22 am by GK »
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Offline GK

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Re: Looking for manufacturer of huge inductor
« Reply #9 on: October 31, 2014, 09:29:42 am »
However, my first choice would be a gapped ferrite such as an E65.


I can only find (have) selector charts for E cores up to 57mm. However the 57mm E core (45724) is significantly less capable than an ETD59:



Extrapolating for that graph, I'm not sure that a 65mm E core would cut it, though they appear to be available up to 100mm. The OP wants an LI2 product in the range of 135 to 180 millijoules and his current design (25A @ 400uH) is 250 millijoules!
« Last Edit: October 31, 2014, 09:35:27 am by GK »
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Offline nctnico

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Re: Looking for manufacturer of huge inductor
« Reply #10 on: October 31, 2014, 08:58:17 pm »
Hi,
I'm working on a high power adjustable DC-DC converter. Because of low frequency (30-60-ish kHz) I have calculated that the inductor I need would be about 150-200uH rated at 30A (ya, i know, it will be large). Do you know a manufacturer that has stuff like that available off-the-shelf? I have shecked typical suspects like Murata, Epcos/TDK, Vishay, Coilcraft, Bourns, TayoYuden and a few others, but they usually don't have anything remotely close to what I need. I'd prefer the manufacturer to be based somewhere in EU, but it's not a hard condition.
Put several in series. Wurth has inductors which can handle that kind of current. They have these in several values and current ratings: http://katalog.we-online.de/pbs/datasheet/7443641500.pdf
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Offline CM800

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Re: Looking for manufacturer of huge inductor
« Reply #11 on: October 31, 2014, 10:05:37 pm »
I would suggest contacting this guy:
www.spwoundcomponents.co.uk

He may be able to help you, hes a really nice folk and has helped me a few times with transformers i have needed making. he should be able to make such an inductor for you easily i would expect. Tell him that Thomas Williamson linked you to him (its not an paid endorsement thing, im just a friend of his) I know he does have ETD59 cores.
 

Offline Conrad Hoffman

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Re: Looking for manufacturer of huge inductor
« Reply #12 on: November 01, 2014, 04:43:05 pm »
I've had similar things wound by a good transformer company on a gapped laminated core. A decent transformer company will do the entire design based on your needs. Around here it would be Tabtronics- http://www.raftabtronics.com/
I'm sure they also ship worldwide.
 

Offline poorchavaTopic starter

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Re: Looking for manufacturer of huge inductor
« Reply #13 on: November 02, 2014, 12:16:53 pm »
I'm curious what is the merit behind using a bobbin-type transformer rather than toroidal one (aside from obviously easier winding process)? Toroids seem to offer better overall parameters. Using the tool from Micrometals website I've come up with inductor that is about 35-40 turns on T249-52 cor. I think I'm gonna use 35*0.355mm litz wire for easier winding.

Peak inductance at low current is then ~330uH falling to about 120uH at 30A. Core losses are under 0.5W, which is nice. Coppers loss will be rather high at around 12-16W. I could bring this down to ~8W using AWG 9 solid copper wire, but that's like 3mm diameter solid wire and it's gonna be a total bitch to wind. I also don't know if the Micrometals software takes skin effect into account.

Since T249-52 doesn't seem to be available from my typical sources (farnell, rs, tme) I may go for bigger size for experimentation phase (eg. T300-52).

I would like to leave engineering by external company as a last resort as this will most likely mean additional time which I don't really have.


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Online David Hess

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Re: Looking for manufacturer of huge inductor
« Reply #14 on: November 02, 2014, 07:17:10 pm »
If you cannot find a standard inductor which will work and do not want to wind your own or pay for custom ones, then I would consider a series and/or parallel arrangement of standard inductors that you can find.

I'm curious what is the merit behind using a bobbin-type transformer rather than toroidal one (aside from obviously easier winding process)? Toroids seem to offer better overall parameters. Using the tool from Micrometals website I've come up with inductor that is about 35-40 turns on T249-52 cor. I think I'm gonna use 35*0.355mm litz wire for easier winding.

E and pot cores which use a bobbin are both easier to wind and you can adjust the core gap.  I often do this when prototyping by winding to fill the window and then adjusting the gap for the desired inductance or peak flux.
 

Offline poorchavaTopic starter

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Re: Looking for manufacturer of huge inductor
« Reply #15 on: November 02, 2014, 08:23:02 pm »
Isn't adding/subtracting windings on a toroid going to vary the inductance as well?

Btw, from what I understand based on various papers I've read over last few days and some calculations it seems, like in this application core losses are very small in relation to copper losses. I think I may be forced to use a large core just to fit all the necessary windings.

I'm limited to either buying an off-the-shelf inductor or winding one myself. My application is quite space-limited so I think that multiple cores in series are out of question.
« Last Edit: November 02, 2014, 09:58:37 pm by poorchava »
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Offline Conrad Hoffman

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Re: Looking for manufacturer of huge inductor
« Reply #16 on: November 02, 2014, 08:33:06 pm »
I'm curious what is the merit behind using a bobbin-type transformer rather than toroidal one (aside from obviously easier winding process)? Toroids seem to offer better overall parameters. Using the tool from Micrometals website I've come up with inductor that is about 35-40 turns on T249-52 cor. I think I'm gonna use 35*0.355mm litz wire for easier winding.

Peak inductance at low current is then ~330uH falling to about 120uH at 30A. Core losses are under 0.5W, which is nice. Coppers loss will be rather high at around 12-16W. I could bring this down to ~8W using AWG 9 solid copper wire, but that's like 3mm diameter solid wire and it's gonna be a total bitch to wind. I also don't know if the Micrometals software takes skin effect into account.

Since T249-52 doesn't seem to be available from my typical sources (farnell, rs, tme) I may go for bigger size for experimentation phase (eg. T300-52).

I would like to leave engineering by external company as a last resort as this will most likely mean additional time which I don't really have.

The answer to your first paragraph is contained in your second paragraph. IMO, 12-16W copper loss seems very high and winding big wire on a toroid is a big PITA. The advantage of external engineering, if they're any good, is that you'll probably do the job once, which is usually the fastest route.

The other difference is that when you buy a powdered metal core, you're buying a built-in fixed distributed gap. With other designs you can adjust the gap, giving you a lot of design flexibility.
 

Offline dannyf

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Re: Looking for manufacturer of huge inductor
« Reply #17 on: November 02, 2014, 08:34:51 pm »
Quote
150-200uH rated at 30A

Wouldn't a power transformer more than sufficient for that?
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Offline nctnico

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Re: Looking for manufacturer of huge inductor
« Reply #18 on: November 02, 2014, 08:42:36 pm »
I would like to leave engineering by external company as a last resort as this will most likely mean additional time which I don't really have.
In my experience having a transformer or inductor wound still means you have to do all the math and testing.
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Online David Hess

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Re: Looking for manufacturer of huge inductor
« Reply #19 on: November 03, 2014, 05:53:55 am »
Isn't adding/subtracting windings on a toroid going to vary the inductance as well?

Adding and subtracting from the windings on a toroid changes the inductance in a very predictable way but it is easier to adjust the air gap on a pot or E core if necessary.  It is much easier if more than one winding or tapped windings are involved.  This is more important during development or if production runs are small.

If I am not sure where I am going to end up during developement, I find the largest E or pot core which will fit in the space required, fill the winding window with copper, and then adjust the gap for either the desired inductance or more likely to a point where the copper and core losses are balanced.

Quote
Btw, from what I understand based on various papers I've read over last few days and some calculations it seems, like in this application core losses are very small in relation to copper losses. I think I may be forced to use a large core just to fit all the necessary windings.

Iterative designs tend to balance the core and winding losses for the most economic solution.
 

Offline GK

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Re: Looking for manufacturer of huge inductor
« Reply #20 on: November 03, 2014, 01:34:26 pm »
If I am not sure where I am going to end up during developement, I find the largest E or pot core which will fit in the space required, fill the winding window with copper, and then adjust the gap for either the desired inductance or more likely to a point where the copper and core losses are balanced.


To support a given L-I-squared product, for a core of sufficient size, there is a minimum gap size and associated AL value. The latter determines the number of turns required for the desired inductance value. You can't just fill the window with a (presumably arbitrary) number of turns and then gap for the desired inductance. If you wind too few turns you'll then have to gap for an AL too high to support the LI2 product and if you wind too many turns you'll have to gap for an AL value below the manufacturers recommended minimum for that particular core, which negatively effects efficiency in other ways.

Also, could you point to a readily available pot core large enough to support the OP's predicted LI2 range?



« Last Edit: November 04, 2014, 10:52:55 am by GK »
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Offline GK

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Re: Looking for manufacturer of huge inductor
« Reply #21 on: November 03, 2014, 01:35:53 pm »
I've had similar things wound by a good transformer company on a gapped laminated core. A decent transformer company will do the entire design based on your needs. Around here it would be Tabtronics- http://www.raftabtronics.com/
I'm sure they also ship worldwide.


Iron laminate? for a SMPS operating at a few 10's of kHz?
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Offline Conrad Hoffman

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Re: Looking for manufacturer of huge inductor
« Reply #22 on: November 03, 2014, 02:31:06 pm »
It was a very similar application, resonant booster, a couple kHz, several hundred watts. I can't remember exactly what the core design was, but it was steel and it wasn't a toroid. There may be some crossover frequency where ferrite is better, but I remember everything we did with ferrite wasn't as efficient. We also wound about 1 toroid and said the heck with that! The advantage of working with a winding house is they'll typically have a large stock of different cores, and will do all the calculations with a very high degree of certainty, assuming you can describe the exact operating conditions. They know their materials and do it every day. That part about knowing your operating conditions is critical.
 

Offline poorchavaTopic starter

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Re: Looking for manufacturer of huge inductor
« Reply #23 on: November 03, 2014, 04:18:07 pm »
After speaking to our company's SMPS guru, I think I'm gonna settle with large material 52 core or alternatively an MSS core (although I can't find a local source for a Sendust core of required size). I will most likely use material with high permeability to wind fewer turns and use 2 or 3 strands of thick lot wire which should bring the copper losses down significantly.
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Offline T3sl4co1l

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Re: Looking for manufacturer of huge inductor
« Reply #24 on: November 04, 2014, 01:12:23 am »
It was a very similar application, resonant booster, a couple kHz, several hundred watts. I can't remember exactly what the core design was, but it was steel and it wasn't a toroid. There may be some crossover frequency where ferrite is better, but I remember everything we did with ferrite wasn't as efficient. We also wound about 1 toroid and said the heck with that! The advantage of working with a winding house is they'll typically have a large stock of different cores, and will do all the calculations with a very high degree of certainty, assuming you can describe the exact operating conditions. They know their materials and do it every day. That part about knowing your operating conditions is critical.

Once upon a time, I designed a 10kW inverter, 600-2000Hz.  Got a 20kVA toroid, stripwound core (3 mil GOSS), some internal cooling (a copper water pipe wound around the core a few times).  A foot across, 30 pounds, $700.  Not bad considering.  Bridgeport Magnetics, I think was the supplier.  Funny, because we quoted half a dozen other companies, whose replies ranged from "no quote" to a monster two feet across (and over $3000)!  Gives you some idea what companies actually know how to do design.

If it were much higher (maybe >3kHz), ferrite would've been just barely preferred I think.  There's also nanocrystalline material, but the price goes way up when you're talking that stuff.

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