Author Topic: Looking for High power Inductor (Read 6131 times)

qwaarjet · « **on:** April 29, 2016, 06:25:11 pm »

I have need to to do performance testing on a custom solid state relay design. For inductive testing I want a ~300-500mH inductor with resistance less than 15ohms and capable of >2A. I haven't had any luck from the regular distributors Digi, Mouser, Coilcraft, ect. Anyone know a manufacturer out there with something in this power range?

bktemp · « **Reply #1 on:** April 29, 2016, 06:58:24 pm »

https://www.hammfg.com/electronics/transformers/choke

Marco · « **Reply #2 on:** April 29, 2016, 08:36:08 pm »

If you need it fast, digikey has this. Just series 10 of them. It's always going to be an expensive chunk of copper ...

ZeTeX · « **Reply #3 on:** April 29, 2016, 08:48:15 pm »

500mH or 500uH?
500mH at 2A is insane, it will be giant and expensive, do they even make those things?

Maybe try putting 2 of those in series:
https://www.hammfg.com/electronics/transformers/choke/193
Part Number: 193U

station240 · « **Reply #4 on:** April 29, 2016, 08:50:21 pm »

Another option is to have it custom made.
I have this company on my list, I know there are many others.
http://www.ecraftsmen.com/

IconicPCB · « **Reply #5 on:** April 29, 2016, 11:47:25 pm »

A local mob

www.gayrad.com.au

uncle_bob · « **Reply #6 on:** April 30, 2016, 12:10:06 am »

Quote from: qwaarjet on April 29, 2016, 06:25:11 pm

I have need to to do performance testing on a custom solid state relay design. For inductive testing I want a ~300-500mH inductor with resistance less than 15ohms and capable of >2A. I haven't had any luck from the regular distributors Digi, Mouser, Coilcraft, ect. Anyone know a manufacturer out there with something in this power range?

Hi

Just taking your current and resistance, I^2 * R will be 60W. That's not a "60W part", it's a part that cooks off 60W when run at your levels. If it is 90% efficient, it would be a 600W part.

Now for another key question:

Is it AC at 2A or DC at 2A? The reason for the question is core magnetization / saturation. You can get away with a bit more sneaky stuff on an AC part.

The final question would be frequency. Since it's an SSR, I assume it is low frequency.

More or less, you are looking for a 500 to 1,000 KVA transformer wound as a choke. That puts it out of the Digikey league and into the "call a transformer manufacturer and get a quote" region. Will that quote come in under $1/ KVA ... only one way to find out. (hint: If it's custom, It depends a *lot* on how many you are buying.)

Bob

qwaarjet · « **Reply #7 on:** April 30, 2016, 12:58:36 am »

Yes it is a monster inductor at .3-.5H and 60 watts is the amount a power I want to dissipate. frequency would be 0-100hz
the purpose of all this is load the system down and then give it a hard inductive kick when it de-energizes the coil. Basically this would be the worst case scenario for this system. The inductor be installed automated test jig that will stress test the hardware before deployment. Currently we use a resistor bank in this sort of testing but want to upgrade to a more realistic test.

IconicPCB · « **Reply #8 on:** April 30, 2016, 01:01:15 am »

A 200mH , 100Arms ( 50Hz ) air cored inductor.. one off.. approx 600AUD

IconicPCB · « **Reply #9 on:** April 30, 2016, 01:03:00 am »

Qwarrjet..

Is this to simulate a relay coil?

IF so.. get a few of THE RELAYS and run them in parallel for that kick in the guts jolt in lieu of the coil.

qwaarjet · « **Reply #10 on:** April 30, 2016, 01:39:10 am »

Industrial solenoid valves mainly, and yes taking a bunch of the coils off the valves is an options but the form factor sucks and its going to be loud with all the clicking.

uncle_bob · « **Reply #11 on:** April 30, 2016, 02:09:05 am »

Quote from: qwaarjet on April 30, 2016, 01:39:10 am

Industrial solenoid valves mainly, and yes taking a bunch of the coils off the valves is an options but the form factor sucks and its going to be loud with all the clicking.

Hi

One of the variables in this is the Q of the coil. With some coils, pulling them off of the equipment has a fairly significant impact on the magnetic environment. That can change the Q and possibly the inductance as well.

Bob

johansen · « **Reply #12 on:** April 30, 2016, 02:17:19 am »

500mh at 2 amps is 1 joule.

60 watt power dissipation at 2 amps of current, you could pull this off with two microwave oven transformer cores. Might be possible with just one core if it's particularly large is 300mh is ok. I can give you some estimate of wire size, air gap and turns count later.

peter.mitchell · « **Reply #13 on:** April 30, 2016, 02:20:53 am »

look into solar panel inverter output filter inductors, 10a 1h is pretty common, parallel it up for your 0.5

IconicPCB · « **Reply #14 on:** April 30, 2016, 02:59:52 am »

10A, 1H... aircored..OK

Ferrite cored?

??

amspire · « **Reply #15 on:** April 30, 2016, 03:18:11 am »

If you want to learn a bit about the joys of designing magnetics, you can have a go at making something yourself, particularly if you have some kind of old steel core transformer that looks like you might be able to pull it apart. Unfortunately, they are much better at impregnating the steel leaves with varnish then they once were, so pulling the leaves apart with modern transformers is hard.

To handle the DC current and to maintain a constant inductance over the DC current range, the transformers has to have a gap - something normal mains transformers do not have. So you have to rearrange the E-I leaves so you can have a gap (all the E's together, all the I's together.) I think it has to be a steel core to handle the DC at a high inductance. Ferrite cores will just need too many turns.

Then you get to the fun mathematics to find the minimum gap, and from that the number of turns, and from that the size and resistance of the windows. Easier to buy an inductor, but if you do have to make something, you can end up with an inductor that performs well.

qwaarjet · « **Reply #16 on:** April 30, 2016, 03:40:58 am »

I don't really want a go DIY route for this, as fun as that would be my my boss would probably hit me if I did:rant:
For this particular application I don't really care about the magnetic performance of the coil, I'm looking at this a form factor and reliability stand point. Also I'm going to need several of these, how many will come down to cash or the amount of space I have left in the box whichever runs out first. In an Ideal world I would have like 128 of them but that ain't happen so I'l end up MUXing whatever I do get.

amspire · « **Reply #17 on:** April 30, 2016, 03:53:55 am »

Triad Magnetics have a C-56U inductor that is 0.035H 2A DC 0.79 ohms. About $22 in Australia so it is probably half that in the US.

10 of them in series would make 0.35H at 7.9 ohms for something around $100.

http://catalog.triadmagnetics.com/item/inductors-and-chokes/low-frequency-inductor-chokes/c-56u-1
http://catalog.triadmagnetics.com/viewitems/inductors-and-chokes/low-frequency-inductor-chokes

Marco · « **Reply #18 on:** April 30, 2016, 04:04:49 am »

That's the one I linked at digikey.

qwaarjet · « **Reply #19 on:** April 30, 2016, 04:12:22 am »

yea doing it that way is not very space efficient. what I cant figure out is when I take one one of my solenoid coils they have 100s of mH at at few 10s of ohms and they aren't very big yet the fixed inductor are huge what gives with that. I want something with that kind of performance with a proper mounting flange and no moving part.

amspire · « **Reply #20 on:** April 30, 2016, 05:22:15 am »

The reason for the size discrepancy only becomes obvious when you start trying to design magnetics.

Those solenoids will be very highly optimized for the job they do - they will have taken the wire temperature to the reliable limit and the magnetic saturation to the limit.

Here is what happens. You design an inductor that is the perfect size and has the right inductance, but too much resistance. The only solution is to use a thicker wire, but to do that you have to increase the winding cross sectional area of the inductor - you have to either make the magnetic path longer or the magnetic cross sectional area smaller. Both of these reduce the inductance/turn so you need even more turns of wire just to even get back to the same point you were at with the smaller core. So you have to choose an ever thicker wire again which might mean an even bigger core. It is not an exponential growth in size, but sometimes it feels like it is. For a design, you might start with a cheap 35mm E core that almost does the job, and end up with a 55mm E core that costs 5 times as much. Getting that perfect size that exactly does the job and exactly has the resistance you want with the wires almost filling the bobbin is a genuine art.

If you did use the solenoids from the valves, you can always fill them with epoxy so the solenoids do not move or click.

qwaarjet · « **Reply #21 on:** April 30, 2016, 05:59:08 am »

I figured it was something along those lines. was hoping to find something COTS with those parameters though

epoxying the the solenoid isn't a bad idea, that thought didn't cross my mind.

SeanB · « **Reply #22 on:** April 30, 2016, 07:08:05 am »

Just replace the solenoids with a steel bolt. Serves as a good approximation for the core, and as a bonus you then can use the bolt to hold it down to a steel plate to handle the cooling. Just use a locking compound on the thread into the plate and a low tightening torque. or use a nut each side and snug up the first nut so the coil can still just turn.

amspire · « **Reply #23 on:** April 30, 2016, 07:34:53 am »

Quote from: SeanB on April 30, 2016, 07:08:05 am

Just replace the solenoids with a steel bolt.

Might work, but it is running at 100Hz rather then DC and I guess it is meant to behave like the real solenoids.

SeanB · « **Reply #24 on:** April 30, 2016, 08:17:08 am »

You drop a bolt in the hole in industrial use when you want to have a powered solenoid non operational, It buzzes just like the real core ( which is a solid iron slug in a stainless steel case) and does the same increase in inductance. Just use a 3/8in M10 bolt, which just about is a snug but loose fit in the hole. Bigger solenoids a 1/2in or M12 bolt fits. You need to use a nylock nut or 2 nuts jammed together as the vibration will loosen a single nut.


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Author Topic: Looking for High power Inductor (Read 6131 times)

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