Maximizing Winding Area in Coil Design: Benefits and Considerations

[hobbs125]

I have been reading about coil design and I have a question.

Is there any specific reason a coil design should utilize the entire winding area?

I keep reading about this in different literature but none of the literate i have read explains why.

 

[berkeman]

I have been reading about coil design and I have a question.

Is there any specific reason a coil design should utilize the entire winding area?

I keep reading about this in different literature but none of the literate i have read explains why.

Can you provide a link or two where this is discussed? What kind of magnetics are you talking about here -- inductors or transformers?

There are winding techniques for transformers that help to minimize the leakage inductance Lk, and other techniques to minimize the parasitic winding-to-winding capacitance Cww. Those techniques may be related to what you are referring to...

 

[hobbs125]

Yeah, I'm talking about wideband transformers.

I was thinking it had to do with leakage inductance but I'm not sure.

 

[berkeman]

Yeah, I'm talking about wideband transformers.

Can you provide a link to the statement, or else type the exact statement here? A diagram would also help.

 

[hobbs125]

Ok, I know I read it somewhere. I've got so many papers saved on my computer I can't seem to find it.

Can anyone here tell me why one should fill all the avialable winding space in a coil?
Are there negative effects to not utilizing all the space?
I tend to think it's just suggested so that the coil design cost is minimized by not using too large a core?

 

[berkeman]

Ok, I know I read it somewhere. I've got so many papers saved on my computer I can't seem to find it.

Can anyone here tell me why one should fill all the avialable winding space in a coil?
Are there negative effects to not utilizing all the space?
I tend to think it's just suggested so that the coil design cost is minimized by not using too large a core?

Well I mosty wanted to see the context of the statement -- there are a number of tradeoffs in wideband transformer design.

Certainly cost is a big deal, and maximizing the winding area useage can be a part of minimizing the cost. However, if you make the core cross-sectional area too small, and fill up the bobbin with windings, you risk running into core saturation issues.

So you look at the different size cores available, and the permeability numbers, and the sizes of bobbins that are compatible with the core. The size of the wire you choose depends on the bobbin area and the currents that will flow in the windings. Once you have an initial estimate on the number of turns based on the core and bobbin, you do the calcs to see if you are close to saturating the core or not.

The winding configuration is usually aimed at attaining the required magnetizing inductance Lm while minimizing the leakage inductance Lk and keeping the Cww low. If you have any more specific questions about transformer design, we can address them here.

 

[vk6kro]

For a given number of turns, you can use a larger diameter wire if you fill up the winding windows than if you don't fill it.

So, this reduces the resistance of the winding and hence the losses.

From a mechanical view, filling the window prevents the wire moving in the window. This reduces hum and possible damage to the winding.