# Plate Choke calculation

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#### swordsman

Hello,

I will need new plate choke for my project. Due to huge shipping cost involved for 2 pieces of 13lbs plate chokes, i have found a local winder who stock M6 EI silicon steel and is willing to do layer winding.

My requirement is as follow,
1.75" Tongue x 1.75" stack, 50W/500Vrms, 45H, tube operating at 100mA.

I got the size for the choke based on the formula,
VA = (188 x L x I x I) for 60Hz
so
VA = 3 x (188 x L x I x I) for 20Hz
VA = 3 x 188 x 45H x 0.11A x 0.11A = 307 VA
(I = 0.11A instead on 0.1A for some allowance)

So i figured 307VA + stacking factor, a 1.75"x1.75" core size of 340VA should fit the bill.

Can someone tell me how many turns should i be using and what is the airgap per leg on the EI core? What is the flux density distribution involved between the DC and AC element.

I read some books recommending the use of sliding rule with C.R. Hanna curve but can't seem to locate it online. Can someone point me to that?

Or even better, is there free software or spice simulation for DC choke design which i can used for different core size?

Swordsman

#### cerrem

The 1.75" laminations is a bit excessive....
I would recomend 1" laminations for this application....
1.25" at most....
100mA DC idle is a bit excessive for the 45 tube....it also makes the OPT a bit more challenging to design....

What is your objective with the 45 tube...
Are you using just one tube. or is there more than one tube paralleled?
What power do you want???
Is the 45H different from the 45 ???
Do you have curve sheets??

The determination of Henries to use on the choke is a function of the plate resistance and where you want to place your -3dB low frequency rolloff POLE.....

Chris

#### AndreK

Number of turns=3750,
gap=.01" per leg
Bdc about 9000 gauss @ mu=500, I=110mA, L=44H

Good luck.

#### cerrem

AndreK said:
Number of turns=3750,
gap=.01" per leg
Bdc about 9000 gauss @ mu=500, I=110mA, L=44H

Good luck.

You have the DC flux density listed..... but you need to add in the AC flux density from the audio signal and sum them for a total net FLUX density.... What is the -3dB POLE when using 44H ??

Chris

#### swordsman

cerrem said:

What is your objective with the 45 tube...
Are you using just one tube. or is there more than one tube paralleled?
What power do you want???
Is the 45H different from the 45 ???
Do you have curve sheets??

Cerem,

think you have misunderstood my post. I'm looking at 45Henry plate choke to be used with a 5.6K parallel feed output transformer. Am not using a 45 tube.

This plate choke will be used for a transmitting tube with a rp of 1.2K~1.5K ohm. Taking rp of 1.5Kohm and 45H, the -2db point will be 10.6Hz. If taking the plate choke of 5.5Kohm, the -3db power will be around 20Hz.

#### JPS

I think you should choose lamination with
1.5" center limb and keep 1.5" stack.

7500 turns of 30AWG. Insulation with polyester sheet of
2 mil thick after every 500 turns. You can increase number of
turns if you see some more winding space in bobbin.

regards

#### JPS

Gap should be given with 10mil thick paper.

#### AndreK

Plate choke

To JPS:
How did you come up with 7500 turns? That choke will saturate well below 110 mA DC with that number of turns. There is a little more involved than just "winding space in the bobbin". The subject is a plate choke, not a grid choke where you can go with as many turns as your bobbin will take, and where is no DC current.
If you have any questions, I'd be glad to discuss them with you.

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