The following bibliography references 60 years of selected academic studies (with clarifying comments enclosed in {}), which confirms the benefits and challenges surrounding the symmetric multiphase doubly-fed synchronous electric motor or generator system with active multiphase winding sets wirelessly placed on the rotor and stator assemblies, respectively, within the same electric motor package footprint of materials, cost, and loss of all others. For instance, the symmetric multiphase doubly-fed synchronous electric motor or generator system (as only now provided by SYNCHRO-SYM) at least provides double power density and octuple peak torque, while improving efficiency and lowering cost, over all other electric motors but only possible with the practical enabling invention of a brushless real time emulation controller (BRTEC):

“The double-armature machine {similarly known as the symmetric synchronous doubly-fed electric motor as only provided by SYNCHRO-SYM} has many merits…continuous power rating is double…in addition…a maximum pull-out torque of…eight times nominal frame size torque rating.”  [1]

“…the power electronic converter {of SYNCHRO-SYM} only has to handle a fraction of the total power…losses in the power electronic converter can be reduced…the cost…becomes lower.” [2]

“…the doubly-fed synchronous electric machine {of SYNCHRO-SYM}…which allows full advantage…from the possibility of delivering energy to both the rotor and stator…create unstable operation…the desirable steady-state features of this machine are not available…” [3]

“The controller requires too many measurements and off-line computations… {unlike BRTEC of SYNCHRO-SYM, the field-oriented controller (FOC) is not brushless, uniformly bidirectional, instantaneous, sensor-less, automatic, which quickly leads to instability}” [4]

With the discovery of a practical rare-earth permanent magnets or RE-PM (circa 1980) that eliminated the cost, size, and loss of electric motor magnetizing MMF and with the formidable challenges of inventing a practical BRTEC, research on the pinnacle of electric motor systems, which is the symmetric multiphase doubly-fed synchronous electric motor or generator system as only now provided by SYNCHRO-SYM, was effectively abandoned in favor of RE-PM electric motor systems. Because of disregard to the environmental impact and human suffering of mining and manufacturing RE-PMs, the CCP has become the major producer of RE-PMs with serious geopolitical consequences, such as also insidiously becoming the market controller of RE-PMs or the major manufacturer and researcher for all electric motor systems, which will propel the revolution in electric transportation. For example, the cost, size, and loss of magnetizing MMF are being retrofitted into RE-PM electric motor systems to gain the coveted benefit of field weakening but ironically, field weakening (as only provided by magnetizing MMF) was already more reliably, efficiently, and cost effectively available with inductions electric motor systems and at another half cost, size, and loss with SYNCHRO-SYM.


[1]   W. F. Long and N. L. Schmitz, Cycloconverter Control of the Doubly-fed Induction Motor,” IEEE Transactions on Industry and General Applications, Vol. IGA-7, No. 1, January/February 1971, Page 95-99.

[2]   A. Petersson, L. Harnefors, and T. Thiringer, “Evaluation of Current Control Methods for Wind Turbines Using Doubly-Fed Induction Machines,” IEEE Transactions On Power Electronics, Vol. 20, No. 1, January 2005, pp. 227-235.

[3]   D. W. Novotny and N. L. Schmitz, “Parametric Pump-Down of Synchronous Machine Oscillations,” AIEE Great Lakes District Meeting, Fort Wayne, Ind., April 25-27, 1962. Page 652-657.

[4]   Y.L. Abdel-Magid, A. H. M. A. Rahim, M. A. Al-Yadoumi, “A Quasi-optimal Stabilizing Control of Power Systems With Dual-Excited Machines,” 1991 IEEE Industry Applications Society Annual Meeting, 28 Sept-4 Oct 1991, ISBN: 0-7803-0453-5.