I would like to ask if it is possible to use the stator iron core of a motor as the toroid core for a transformer. The original windings from a bad motor would be removed, and a single coil would be wound in such a way, as to keep the magetomotive force evenly distributed along the axis of the entire core. Such a core is segmented. In each segment a constant number would be wound. The segments would cause some magnetic flux to flow through their air gap, but that should be very small, as the permeability of air is too low. The secondary would be wound to also keep the number of turns per segment constant.
The electrical difficulty of such an arrangement is that each segment would act as an independent transformer to some extent, but this independence is slight, as the main flux passes along the entire core axis path.
If a rotor core is generously wide, one can saw off the segment sides to leave only a toroid which should behave like other mangetic toroids. The difference would be that such a core would consist of a stack of rings instead of long strip wound on itself to form a ring.
The electrical difficulty of such an arrangement is that each segment would act as an independent transformer to some extent, but this independence is slight, as the main flux passes along the entire core axis path.
If a rotor core is generously wide, one can saw off the segment sides to leave only a toroid which should behave like other mangetic toroids. The difference would be that such a core would consist of a stack of rings instead of long strip wound on itself to form a ring.
I found this when I searched... Using old stator housing (iron rings) as transformer core? Possible? | All About Circuits
Maybe there's useful information for you - I don't wind my own coils 😀
Koda
Maybe there's useful information for you - I don't wind my own coils 😀
Koda
The stator teeth should not be a problem, even if you're unable to remove them for some reason. However, unlike toroidal transformers, stator cores are usually wound for radial (and not axial) flux.
Nevertheless, axial flux motors do exist and yes, many have successfully used transformer-grade laminations, no problems at all.
Nevertheless, axial flux motors do exist and yes, many have successfully used transformer-grade laminations, no problems at all.
It should work, but since the cross-section is not uniform, you have to compute the induction/volt per turn based on the smallest part of the section.
This means that a lot of the iron will remain underused.
This means that a lot of the iron will remain underused.
Thanks for all replies.
Considering the Physics, the answer to my question is a Yes. I asked just in case someone has already tried to do it before me. Although, I have never built my own transformers, being able to do so using materials from other transformers and motors, is an avenue that may be helpful in case transformers become obsolete. Switching power supplies are clearly becoming the industry standard of many many manufacturers.
Therefore, an old hag like me, who like other old hags like to twiddle with obsoleted stuff like thermionic valves, having more options is more than welcome.
In my case, I would saw off the stator teeth and make sure to use a stator core with a uniform circular shape. This should present the same magnetic resistance at all points along its circular axis. Another very important point to consider is to avoid having shorted turns formed by having the rings welded together. Such welding has to be removed.
The appealing aspect of using a motor core, is some motors have several inches of core thickness. This can help using a large core to wind a transformer with a maximum flux density that is well below saturation (Bsat for iron is about 1.5T). A maximum flux density below 1T, I think 0.8T would make a beautifully cool transformer, can be achieved this way.
With a cross sectional area A and maximum flux density B, using a sinusoidal power voltage:
V = d/dt {B.A.sin(2.pi.f.t)}
V = 2.pi.f.B.A.cos(2.pi.f.t)
At the maximum, cos(...) = 1.
Therefore: Vm = 2.pi.f.B.A
For an RMS voltage U, the voltage per turn would be:
U = Vm/sqrt(2) = 2.pi.f.B.A/sqrt(2)
==>> U = sqrt(2).pi.f.B = 4.44*f*B*A
In the case of Europe, 50Hz supply:
222*B*A
All units are SI (I did my A-Level Physics in 1986).
Considering the Physics, the answer to my question is a Yes. I asked just in case someone has already tried to do it before me. Although, I have never built my own transformers, being able to do so using materials from other transformers and motors, is an avenue that may be helpful in case transformers become obsolete. Switching power supplies are clearly becoming the industry standard of many many manufacturers.
Therefore, an old hag like me, who like other old hags like to twiddle with obsoleted stuff like thermionic valves, having more options is more than welcome.
In my case, I would saw off the stator teeth and make sure to use a stator core with a uniform circular shape. This should present the same magnetic resistance at all points along its circular axis. Another very important point to consider is to avoid having shorted turns formed by having the rings welded together. Such welding has to be removed.
The appealing aspect of using a motor core, is some motors have several inches of core thickness. This can help using a large core to wind a transformer with a maximum flux density that is well below saturation (Bsat for iron is about 1.5T). A maximum flux density below 1T, I think 0.8T would make a beautifully cool transformer, can be achieved this way.
With a cross sectional area A and maximum flux density B, using a sinusoidal power voltage:
V = d/dt {B.A.sin(2.pi.f.t)}
V = 2.pi.f.B.A.cos(2.pi.f.t)
At the maximum, cos(...) = 1.
Therefore: Vm = 2.pi.f.B.A
For an RMS voltage U, the voltage per turn would be:
U = Vm/sqrt(2) = 2.pi.f.B.A/sqrt(2)
==>> U = sqrt(2).pi.f.B = 4.44*f*B*A
In the case of Europe, 50Hz supply:
222*B*A
All units are SI (I did my A-Level Physics in 1986).
Your maths look OK.
If you are ready to undertake the chore of manually winding a toroidal (think of the primary!), why not.
Be aware that if you try to spread the winding regularly along the core, some parts will need extra lengths of copper wire, and if you confine the winding to the narrowest parts, you will increase the leakage inductance. But it can certainly be made to work.
If you are ready to undertake the chore of manually winding a toroidal (think of the primary!), why not.
Be aware that if you try to spread the winding regularly along the core, some parts will need extra lengths of copper wire, and if you confine the winding to the narrowest parts, you will increase the leakage inductance. But it can certainly be made to work.