plate choke inductance at rated current

[ee]

I'm looking at plate choke ratings.
- (plate) choke has a rated inductance measured at a current. Is the actual inductance dependent on the choke's current around that measured rating?
For example, using a rated plate choke that's 50H @ 60 ma in a circuit whose constant current is 30 ma the H would increase perhaps 2x since the current was half of rated measurement?
If the H does change is there a good estimate for what H might be based on current if I don't have equipment to measure?
Thank you for your help.
Eric

 

[Paul Birkeland]

Yes, the inductance will go up a bit, but I wouldn't expect 2x.

You can buy a cheap LCR meter and measure the inductance with no AC current.  The inductance at 30mA will be somewhere between that number and 50H

 

[Paul Joppa]

There is a continuum of choke designs, which I think of as three varieties:

1) Designed for large AC flux and small DC flux

2) Designed for comparable levels of AC and DC flux

3) Designed for large DC and small AC flux

Type 2 includes series feed transformers and parallel feed plate chokes. These are sometimes called "linear inductors" because the air gap dominates the AC permeability over a wide range of AC flux. For these, the inductance decreases slowly with the DC flux, typically falling less than 20% at maximum DC current, depending on design choices.

Note that Type 3 is typical of power supply filter chokes. To use regular filter chokes as parafeed inductors, it's a good idea to de-rate the DC current by 20-50% to leave some flux range for the AC currents.

The above notes are still a gross simplification of plate choke performance, but this is a forum post, not a textbook  :^)

 

[Paul Birkeland]

The above notes are still a gross simplification

I thought that was my post!