EMI CHOKE QUESTION

Yes. And, for extreme cases, you can consider using coaxial cable instead of individual wires. Paul Mathews

Ok, thanks Paul.

I just finished winding a choke bifilar and the inductance stayed constant up to 50amps.

Unfortunately my supply only goes to 50amps. I would like to get flavor at 150amps.

I may look at a Rubadue style wire to wind units.

regards, Bob

Good point. Cross-winding midway around takes care of that problem. Paul Mathews

dont forget that although the flux on each side of the toroid cancel eachother out so there is no circular flow around the core, they do however add up to cuase a net flux across the core, wich if high enough wil cuase enough flow through the air to saturate the whole core.

Colin =^.^=

Colin, Paul,

Seems you two have lost me. Not sure what a net flux across the core is, and cross-winding is a term I'm not so familiar with.

One thing I did realize is that winding bifilar will tend to decrease the differential mode inductance - So differential noise components might then actually be worse.

regards, bob

Colin, Paul,

Seems you two have lost me. Not sure what a net flux across the core is, and cross-winding is a term I'm not so familiar with.

One thing I did realize is that winding bifilar will tend to decrease the differential mode inductance - So differential noise components might then actually be worse.

regards, bob

Colin, Paul,

Seems you two have lost me. Not sure what a net flux across the core is, and cross-winding is a term I'm not so familiar with.

One thing I did realize is that winding bifilar will tend to decrease the differential mode inductance - So differential noise components might then actually be worse.

regards, bob

Colin, Paul,

Seems you two have lost me. Not sure what a net flux across the core is, and cross-winding is a term I'm not so familiar with.

One thing I did realize is that winding bifilar will tend to decrease the differential mode inductance - So differential noise components might then actually be worse.

regards, bob

The differential mode component you mention is just leakage inductance between the common mode windings. Most of this flux is 'in the air', rather than 'in the core'. If you absolutely must minimize the number of components in your design, then it may be worthwhile to depend on leakage inductance for DM benefits. However, on the down side, winding methods that increase leakage inductance also increase the likelihood of imbalances that lead to core saturation. At the point when the core saturates, the CM properties of the component pretty much disappear. When you place windings around a core, proceeding uniformly in the same direction, there is a general flow of current in the direction of those windings. For a toroid, this has the unintended effect of one or more 'turns' effectively following the core and producing a field through the core axis rather than within the core material. You can cancel this effect by alternating the direction that the turns advance around the core. 'Cross-winding' of single-layer toroids involves winding ~ half way around the core, 'jumping across the core center to the opposite side, and winding an equal number of turns advancing in the opposite direction around the core. All turns have the same direction with respect to the core itself. Some mfgrs of toroidal inductors always follow this practice. For a horizontally mounted toroid, it's also quite easy to specify 2 windings wound in such a way that they can be series connected to achieve the cross-winding effect. If done properly, cross-winding also reduces the distributed capacitance of the inductor, making it effective at higher frequencies. Paul Mathews

The new beta of Google Groups has a much lower latency than the old iteration.

If you get a Server Error message, wait a minute or 2 and refresh the thread page. Usually your post has gone thru, it's just that the ACK page hasn't come back.

BTDTGTTS

dont use a supply, use a monster cap. Charge the cap up, and "splat" it across the choke. Easy to get 1,000A that way :)

just choose Ecap >> Echoke at Idesired

Cheers Terry

does your system need common mode or differential filtering (or both) to solve the EMI problem?

Mark