Hairpin Motor Using Aluminum Hairpins

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Aluminum is the most cost-effective conductor of electricity available. It can carry electrical current for less than 15% the cost of carrying the same current, using copper. However, aluminum has lower conductivity than copper and the aluminum conductors need to be 1.6 times larger than what would be needed by copper in order to maintain the same performance and efficiency. For this reason, copper is the preferred material for most electric motors and almost all EV motors. However, when copper is replaced by aluminum in a hairpin motor it is found that the AC losses in the aluminum are much less than the AC losses in the copper, when all the AC losses are properly accounted for. In a hairpin motor the AC losses typically exceed the DC losses and the result is that the use of aluminum without any increase in conductor size in a hairpin motor results in very little loss of efficiency.

A recent development called Variable Conductor Area Technology (V-Cat) allows copper to be replaced by Aluminum in EV motors without any loss of efficiency saving considerable cost. V-Cat is a form of hairpin winding in which the end-windings and slot conductors are formed in aluminum using conventional die casting. The end-windings forming part of this conductor are much larger in cross section than the slot conductors. The slot conductors remain the same size as the copper they replace. This allows the overall combined DC and AC conductivity of the windings to equal or lower the original copper losses and so do not negatively affect the performance of the motor or its efficiency.

A typical hairpin motor using copper hairpins consumes around 8kg. of copper costing over $80.00 and this can be replaced by 2.5kg of aluminum costing $7.00. The manufacture of aluminum has significantly less environmental impact than the manufacture of copper. The loss of range for a motor similar to the VW ID3 base range of 346kms is less than 1,5km. Using the V-Cat design the range can be increased by a similar amount.

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  • Name:
    Michael Durack
  • Type of entry:
  • Profession:
  • Michael is inspired by:
    Saving cost on electrified vehicles using innovative design .
    Challenging engineering predjudice .
    Design validation by simulation.
    Reduction in negative environmental impact.
  • Software used for this entry:
    In house software based on Space Vector Pulse Width Modulation (SVPWM)
  • Patent status: