# Halbach array arrangement for transformer?

#### shane88

Joined May 22, 2019
12
Hello,

We know that Halbach array works well with a permanent magnet by giving a strong magnetic field in one side and weak on the other side. Why can't we use this for electromagnets? What would be the disadvantage? Imagine if we use halbach array special arrangements for the transformer instead of an iron core. Maybe it could give us the same result? Kindly advise.

#### crutschow

Joined Mar 14, 2008
26,053
Imagine if we use halbach array special arrangements for the transformer instead of an iron core.
A Halbach array cancels the magnetic field on the opposite side of the magnet since that field is not being used, but the whole magnetic field in a transformer is already contained and used (except for some small leakage) so there would be no improvement in using some type of Halbach array for the magnetic core.

#### shane88

Joined May 22, 2019
12
A Halbach array cancels the magnetic field on the opposite side of the magnet since that field is not being used, but the whole magnetic field in a transformer is already contained and used (except for some small leakage) so there would be no improvement in using some type of Halbach array for the magnetic core.
Thank you for answering,

Can we use Halbach array for the electromagnetic field since the magnet field change with direction? In a permanent magnet, the direction is constant where halbach array arrangement is useful. I'm trying to build a design using Halbach array arrangement using coils to produce high efficiency magnetic field in one direction. I want to know whether i can achieve this using electromagnet by giving alternative current to the coil.

#### shortbus

Joined Sep 30, 2009
8,197
Thank you for answering,

Can we use Halbach array for the electromagnetic field since the magnet field change with direction? In a permanent magnet, the direction is constant where halbach array arrangement is useful. I'm trying to build a design using Halbach array arrangement using coils to produce high efficiency magnetic field in one direction. I want to know whether i can achieve this using electromagnet by giving alternative current to the coil.
No

#### shane88

Joined May 22, 2019
12
Can you explain why?

#### crutschow

Joined Mar 14, 2008
26,053
Can you explain why?
Transformers don't (and can't) use permanent magnets to generate the AC field.
All a DC field would do is cause saturation of the magnetic material,

You need to study how transformers work.

#### shane88

Joined May 22, 2019
12
Transformers don't (and can't) use permanent magnets to generate the AC field.
All a DC field would do is cause saturation of the magnetic material,

You need to study how transformers work.
I want to use a Halbach array configuration for electromagnets using coils to give a strong magnetic field in one side and weak on the other side. I don't want to use any permanent magnet but instead, use 3 to 4 solenoid to arrange in Halbach arrangement. The solenoid also behaves similar to a permanent magnet. I want to arrange solenoid in Halbach array and give pulsed dc to the solenoid coil so the direction won't change, in this way I can achieve Halbach array. I'm only concerned if there will be any eddy current between each solenoid? If you can give me any idea to work this out.

#### crutschow

Joined Mar 14, 2008
26,053
Originally you mentioned a transformer, and now you are talking about a solenoid.
In theory it would work for an electromagnetic, but I'm not sure if it's worth the effort.
I'm only concerned if there will be any eddy current between each solenoid?
Pulsed DC will give few eddy currents.
Why do you want to use pulsed DC?

#### shane88

Joined May 22, 2019
12
Originally you mentioned a transformer, and now you are talking about a solenoid.
In theory it would work for an electromagnetic, but I'm not sure if it's worth the effort.
Pulsed DC will give few eddy currents.
Why do you want to use pulsed DC?
Sorry for the confusing question. My original plan is to create a wireless transmitter using Halbach arrangement to produce a magnetic field. I was thinking if we can find a good solution with Halbach arrangement, it will give a high-density magnetic field on one side which will be beneficial for wireless power transmission technologies. This can also increase efficiency but I don't have any idea beside solenoid design. The major drawback with Halbach in the electromagnetic field is the eddy current and positioning. I was hoping pulsed dc would be an ideal way to get the result because alternative current will change the direction of the field and might cancel out each other. I want to do this for a school project. Any advise or help would be appreciated. Thanks

#### crutschow

Joined Mar 14, 2008
26,053
Well, you could conceivably do a Halbach AC array but I don't think it would have any advantage for AC over just a horseshoe type of solenoid configuration which puts all the magnetic field on one side.

A Halbach array's main advantage is when used with permanent magnets.

#### shane88

Joined May 22, 2019
12
Well, you could conceivably do a Halbach AC array but I don't think it would have any advantage for AC over just a horseshoe type of solenoid configuration which puts all the magnetic field on one side.

A Halbach array's main advantage is when used with permanent magnets.
Thank you for your answer. One last question, If I use Halbach AC array for the wireless transmitter, can it improve the air core efficiency while transferring power to the receiving coil. Will there any efficiency improvement than traditional wireless chargers? Do you know any article or books about Halbach AC array designs and ideas?

Thanks.

#### crutschow

Joined Mar 14, 2008
26,053
Do you know any article or books about Halbach AC array designs and ideas?
I know of none.
As I stated, I think it will have no advantage over standard transformer configurations for AC.

#### shortbus

Joined Sep 30, 2009
8,197
Can you explain why?
Because Halbach arrays are only possible with permanent magnets.

#### TeeKay6

Joined Apr 20, 2019
572
Hello,

We know that Halbach array works well with a permanent magnet by giving a strong magnetic field in one side and weak on the other side. Why can't we use this for electromagnets? What would be the disadvantage? Imagine if we use halbach array special arrangements for the transformer instead of an iron core. Maybe it could give us the same result? Kindly advise.
@shane88
A Google search for "electromagnet Halbach" returns links to several patents and applications for electromagnet Halbach arrays. However, I see no mention of transformers.

#### Yaakov

Joined Jan 27, 2019
1,612
The possibility of using a Halbach array geometry to increase efficiency is interesting but I have the intuitive reaction that in the case of an electromagnetic with a necessarily changing field (in your application), the efficiency gains would be cancelled out by hysteresis or some other effects from the constantly collapsing and reforming field.

This is just a surmise, but TANSTAAFL is a powerful principle, and I suspect it applies here.

#### TeeKay6

Joined Apr 20, 2019
572
A Halbach array cancels the magnetic field on the opposite side of the magnet since that field is not being used, but the whole magnetic field in a transformer is already contained and used (except for some small leakage) so there would be no improvement in using some type of Halbach array for the magnetic core.
@Imagine a transformer comprising two flat coils (pri & sec) aligned on a common axis--two pancakes in a stack with a thin separating layer of air. I believe such a transformer is conceptually what is used in many "wireless chargers" now being investigated (for charging cellphones, earphones, etc). Surely it would be advantageous if the field of the coils could be concentrated toward the air space between them? Of course, there is a great difference between being conceptually beneficial and being actually and economically feasible.