# Switched reluctance motor



## dillond666 (Dec 27, 2010)

I watched an interesting video on Youtube yesterday where the guy was making petal valves for a pulsejet engine. He used a saltwater bath and a battery charger to etch through the steel plate. He used spraypaint to act as etch resist. Could be a useful technique for experimentation purposes.


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## PStechPaul (May 1, 2012)

Check the thread:
http://www.diyelectriccar.com/forums/showthread.php?t=77483&highlight=switched+reluctance

I may get back to doing some work on this again, but I'm recuperating from hip replacement surgery April 22. Apparently it is not necessary to use laminations for this design. Just a solid block of steel or soft iron machined into a rotor will work, or the magnetic material (not magnets) can be molded into a plastic or ceramic rotor. Since it does not rely on induction and current flow in the rotor, eddy currents and rotor conductor losses are not a factor.

It's difficult to rebuild an ACIM into a SRM. The laminated rotor is just about impossible to machine, and the stator is not designed for SRM. However, I have a small fan motor with six pole pieces that might work.


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## cts_casemod (Aug 23, 2012)

PStechPaul said:


> Check the thread:
> http://www.diyelectriccar.com/forums/showthread.php?t=77483&highlight=switched+reluctance
> 
> I may get back to doing some work on this again, but I'm recuperating from hip replacement surgery April 22. Apparently it is not necessary to use laminations for this design. Just a solid block of steel or soft iron machined into a rotor will work, or the magnetic material (not magnets) can be molded into a plastic or ceramic rotor. Since it does not rely on induction and current flow in the rotor, eddy currents and rotor conductor losses are not a factor.
> ...


Hi Paul,

First of all, I wish you a quick recovery,

Yes I had a read on your topic in fact I was going to send you a PM sometime. I Know ABB for sure is doing what i plan for their new generation IE4 Efficiency motors. They also Claim to obtain almost double the power with standard efficiency










I was pareticuallary interested in the fact that this motor does not rely on any EMF, so the inverter is easy to design, with less parts, and no need for fancy since wave, so Silent operation and high efficiency

I checked a few topics where people are actually machining the rotor of an induction motor to make ir syncronous, I guess thats basically what they are doing - creating a SRM. Yet, the way you show it in your topic looks more a bit different of how I planed to do it, a bit more like the concept of a brushless DC


http://www.hvtesla.com/sync_motor.html










Not the way i was planing on doing it, but it might give some ideas. As far as I know this setup reverts back to asyncronous if the maximun torque is exceeded.


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## PStechPaul (May 1, 2012)

Well, t appears that the laminated rotor can be machined. I had a hard time with it, but my machine tools are not the best, and my experience is minimal. In the link you supplied, it seems that the main emphasis was on making a synchronous machine for precise firing of spark gaps for some purpose. As such, the motors probably did not need to produce much torque.

But that gives me an idea. Maybe an external mechanical commutator could be devised to discharge a capacitor into a winding that produces torque in the right direction at the right time to continue rotation. And the electromagnet pole piece could be part of an LC resonant circuit that would continue to make a magnetic field for a while as the rotor turned, since the polarity of the field does not matter for a SRM.


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## cts_casemod (Aug 23, 2012)

PStechPaul said:


> Well, t appears that the laminated rotor can be machined. I had a hard time with it, but my machine tools are not the best, and my experience is minimal. In the link you supplied, it seems that the main emphasis was on making a synchronous machine for precise firing of spark gaps for some purpose. As such, the motors probably did not need to produce much torque.
> 
> But that gives me an idea. Maybe an external mechanical commutator could be devised to discharge a capacitor into a winding that produces torque in the right direction at the right time to continue rotation. And the electromagnet pole piece could be part of an LC resonant circuit that would continue to make a magnetic field for a while as the rotor turned, since the polarity of the field does not matter for a SRM.


 
To be fair I wouldnt do it like that, and regardless it still has a component of induction into the rotor, so efficiency will not be great. The other issue is the Gap - Huge! As you say I would not expect a lot of torque ot at least not with great efficiency.

But hes using standard mains. On our prototypes we would need to use a dedicated controller and here it would be quite easy to impelement using a position sensor. I dont see how it could be made without one (sensorless vector) but I have one here that only has 3 phases and a thermal sesnor, so it must be possible. On my idea the rotor would have the same number of poles as the stator, I would apply current until both were aligned and then I would wait and triger the next phase and so on, giving a rotating efect as they are 60' apart.

The idea I had was, using laminations, somehow machine the rotor and add something that could be bolted into it with a given shape, not exactly using the rotor as it is because much of it is allumnium/copper so not really good for the purpose - in fact it would end up with induced currents and losses we dont want.

Only thing I cant seem to get is how the hell can I regenerate with such a motor!? Maybe activate one phase and recover the energy on the others!?


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## PStechPaul (May 1, 2012)

I don't know if it is possible to obtain regeneration from a SRM, but apparently there ay be a way to do it. Here are a few links I found:

http://papers.sae.org/2007-01-0401/
http://www.rockymountaintechnologies.com/Data Sheets/SRTD-5050.pdf
http://ieeexplore.ieee.org/xpl/logi...re.ieee.org/xpls/abs_all.jsp?arnumber=4771352
http://www.chargedevs.com/content/features-inside/closer-look-switched-reluctance-motors

The last link indicates that regeneration occurs as the magnetized iron of the active rotor pole decreases in inductance past the point of closest alignment (where inductance peaks). If the drive voltage is removed (or reduced) at this point, there should be an inductive "kick" that might be harvested as regeneration.


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## iti_uk (Oct 24, 2011)

I'm still working on mine - I have the laminations for both rotor and stator, but I forgot to ask the machinist to cut the insulation paper with the steel laminations so I'm spending time cutting the paper manually.

Still need to get the endbells machined, but it's all looking promising so far...

Chris


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## cts_casemod (Aug 23, 2012)

iti_uk said:


> I'm still working on mine - I have the laminations for both rotor and stator, but I forgot to ask the machinist to cut the insulation paper with the steel laminations so I'm spending time cutting the paper manually.
> 
> Still need to get the endbells machined, but it's all looking promising so far...
> 
> Chris


Do you have a link? I can only find the laminations topic!


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