Electric Motor Windings
From Open Source Ecology
Stator Winding Design Considerations
- Stator winding design considerations
- In existing mass produced designs slot geometry is designed with automated winding in mind. If willing to manually wind the coils then better parameters can be reached. Consider:
- A trapezoidal-shaped slot area maximizes the winding area available and is commonly implemented when the windings are wound randomly (by automated machine), when they are wound turn by turn without any predetermined orientation in a slot (Hender-shot, 1990). On the other hand, a parallel-sided slot with no shoes is more commonly used when the windings are fully formed prior to insertion into a slot.
- If manually winding a custom designed motor the slot space can be optimized (approach 100% fill). The slot opening can be minimized/removed, replacing air with the magnetic core material of choice to enhance motor characteristics (wide slot opening was needed by winding machine in mass produced designs).
Aluminum vs Copper
- Aluminum windings DO compare well to copper windings based on resistivity and density considerations.
- See resistivity - [1] - aluminum is under 2x more resistive than copper.
- But aluminum density is 2.7 g/cm3 - whereas copper is 9 g/cm3. Thus, >3x as heavy in its density. This means that the weight of windings will actually be lighter for the same current flowing through the winding. Which means that a motor of the same power is likely to be lighter (though larger in size) - unless the non-winding parts of the motor are all together heavier because of the larger volume of the motor.
- The relevance for the GVCS is eliminating the need for copper if aluminum from clay is acceptable - such that an electrical power economy can likewise be produce without strategic resources such as copper.
- This article verify that aluminum-wound electric motors are feasible - [2]
- Aluminum carries 2x the current per pound compared to copper, and is 1/2 to 1/4 the cost - making aluminum windings 4-8 times less expensive than copper windings - [3]
- Aluminum may have more skin effect, and be less efficient for certain high efficiency applications. [4]
- Heat storage capacity of aluminum is 2x as large, so aluminum can withstand larger overlaod conditions - [5]
Cost considerations
- Cost breakdown of transformers indicates ~20% for the windings, ~35% for magnetic steel. -[6]
