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Winding pattern and slot design for electric machines Disclosure Number: IPCOM000249846D
Publication Date: 2017-Apr-17

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The Prior Art Database

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Wen Ouyang: AUTHOR


Variable winding patterns with corresponding slot designs achieve minimized space harmonics in electric machines. With different turns in each coil as well as different slot dimension and distribution position, the space harmonics can be effectively reduced, the slot area can be effectively designed to enhance material utilization, which further benefits machine performance in terms of efficiency and torque pulsation.

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Winding pattern and slot design for electric machines

Many electric machines are designed with the same slot geometry and equal turns per slot nowadays, which set the machine design limits for design space.  However, in many applications, due to the limitation from voltage, current or physical dimensions, the designs with non-equal turns in each slot turn out to be feasible candidates.  With uniform slot dimensions, the machine slot fill suffers for low turn number slots, or the high turn number slot observes difficulty in winding insertion, which is even more severe for designs with low turn number.  In the present disclosure, a design of different turns in each slot with non-equal slot dimension is disclosed to reduce airgap space harmonics, which results in better electric machine design in terms of efficiency and torque ripple.  

The main reasons for utilization of non-equal turns per slot and non-equal slot design are:

a)     With machine ampere*turns, machine winding produces magnetic motive force (MMF) can be optimized effectively with different turns/slot design consideration. 

b)    With low turns in slot, the slot dimension can be shrunk to achieve higher slot fill and less saturation for adjacent teeth.

c)     Slots can be redistributed along inner diameter to balance the difference in each slot ampere*turns to further help the MMF distribution cross the air gap region.

Figure 1:  Typical air gap flux density distribution with fundamental component in orange

In Figure 1, a typical flux distribution for electric machine is illustrated. With slot effect and armature reaction, the air gap flux density observes significant harmonic components.

In the present disclosure, a variable coil turns winding pattern combines with the slot dimension and distribution is proposed. This is achieved by varying the number of turns in each coil of each phase winding with the reduced slot area for the slot with lower number turns.  The main idea is to use the optimized winding pattern with different slot design to achieve less space harmonics and thus the machine losses associated with harmonics can be reduced.  

Fig.2 Magnetic motive force distribution of random concentric two windings.

Figure 2 presents the magnetic motive force distribution of random concentric two windings.

The flux density , are as follow



With Fourior series, the airgap flux density is given by


By superposition principle, the airgap flux density of random position including time and space is given by


Therefore the total airgap flux density is as follows


where,  is the total number of slot

In Table 1, an example of single layer 3 phase winding configuration with 60 degree phase...