Author Topic: DIY Standard Inductors with Reasonable Accuracy and Stability?  (Read 10923 times)

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Offline TimNJTopic starter

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Re: DIY Standard Inductors with Reasonable Accuracy and Stability?
« Reply #50 on: September 13, 2020, 03:56:00 am »
Thanks for sharing. I thought your question was about the inductance value (stability over frequency). For resistance, indeed I would expect litz to read lower.
 

Offline Jay_Diddy_B

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Re: DIY Standard Inductors with Reasonable Accuracy and Stability?
« Reply #51 on: September 13, 2020, 04:12:20 am »
Hi,

Here are the results of the enameled wire inductor from the HP4274A:




The Q is higher for the enameled wire inductor for frequencies 40kHz and lower. This is because the DC resistance is lower, the enameled wire is one wire gauge larger.

At 100 kHz the skin depth has started to show and the Q for the enameled wire is similar to the Litz wire version.


Network analyzer




The impedance versus frequency is very similar. The SRF frequency of the enameled wire is higher. This is because it has a smaller diameter and therefore lower capacitance.

The difference between the Litz wire and the enameled wire isn't all that great especially if you increase the gauge of the enameled wire to the same diameter as the Litz wire.

Summary




Regards,
Jay_Diddy_B

« Last Edit: September 13, 2020, 04:25:22 am by Jay_Diddy_B »
 
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Offline ArthurDent

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Re: DIY Standard Inductors with Reasonable Accuracy and Stability?
« Reply #52 on: September 14, 2020, 12:46:40 am »
Years ago I would bid on Department Of Defense surplus electronic lots, sight unseen. Among other great stuff I got in one large lot that I got for about $0.25 per pound there were two sets (15 values each set) of GR 1482 series inductors that were removed from a calibration lab. That was one of the better buys I ever got.
 

Offline TimNJTopic starter

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Re: DIY Standard Inductors with Reasonable Accuracy and Stability?
« Reply #53 on: September 29, 2020, 03:55:27 am »
So far, I've only had the time to wind one inductor, but I thought I'd share:

For the 1mH inductor:

CSC CM400060 (OD=40mm, 60u, MPP) "Bulk inductance"
~110 turns of 0.45mm UEW enameled wire

CSC CM127060 (OD=12.7mm, 60u, MPP) "Coarse adjustment"
~20 turns of 0.45mm UEW enameled wire

CSC CM039060 (OD=3.9mm, 60u, MPP) "Fine adjustment"
~3 turns of 0.45mm UEW enameled wire

The first two cores are mounted to the housing using 3/8" rubber bumpers, with 3M VHB tape on top of the bumper to make a double-sided 3/8" bumper (if you will). Then, I flooded the housing with clear GE Silicone II. (No photo yet.) It's not the best consistency to work with. Regular flexible potting compound would have been better, but I cannot justify the price. $50+ to fill just two of these little Hammond enclosures.

With the 40mm core only, the closest value I could get was about 1010mH@100KHz, which really isn't so bad. But, figured I could do better. So, I removed a turn and added the 1/2" (12.7mm) toroid. This got the inductance within ~0.2%, so I added a little extra inductance with the 3.9mm toroid to get within 0.1%. However, after finalizing the mounting position in the housing and after "potting" the inductors in some GE Silicone II, the inductance crept up to about 1002mH. So, I removed the small 3.9mm toroid. (Photo shows original configuration with fine adjustment toroid.)

In the end, if you try to make your own, you could just get lucky and not have to bother with any of this.

Also, winding 110 turns on this core requires about 5.5 meters of wire. Took me close to two hours and extreme attention to prevent the wire from kinking, due to its very long length.

The meter I have access to (Extech LCR200) shows between 996 - 997mH @ 100Hz, 1KHz, and 10KHz, and 1000.9mH @ 100KHz. I'd like to check it on a TG + SA or VNA to check its resonant frequency. It seems that the inductance is increasing ever so slightly with frequency.
« Last Edit: September 29, 2020, 03:58:52 am by TimNJ »
 


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