The source-to-wheel efficiency of today’s electrified vehicles already far surpasses the
efficiency of strictly gasoline vehicles. As sources of electricity become cleaner and
more efficient, and as gasoline becomes more scarce, the need for transportation electrification is increasingly economically and environmentally driven. The automotive
industry primarily makes use of permanent magnet synchronous machines (PMSMs)
and induction machines (IMs), the latter has the cost advantage of containing no rare
earth metals. This thesis studies two different induction motors for electrified powertrain
applications using a novel optimization algorithm to create efficiency maps
and compare the efficiencies of the two motors. Induction motors are difficult to
banchmark due to their complicated control schemes. Each point in their operating
range can be achieved with an infinite number of current/slip combinations and
therefore has infinite potential efficiencies. The proposed algorithm limits the number
of simulations needed to benchmark an induction machine, and provides a clear and
unbiased way to compare machines based on losses at their most efficient current/slip
combinations over their entire operating range. The proposed algorithm is able to
calculate losses within 5% accuracy of simulation values for both machines. The first
motor studied makes use of stranded windings and geometry parameters from the
Tesla Motors patents. The efficiency map created has a peak efficiency of 96% and
corresponds closely to an efficiency map for a similar motor found in literature. The
second motor makes use of copper bar windings, which are easier to manufacture and
have lower material costs. Bar windings, typically have lower resistance and stator
copper losses at low speeds, but higher effective resistance and stator losses at high
speeds due to eddy effects. The motor modelled was intended simply to compare the
stranded and bar windings, and to see the advantages and disadvantages. For this
reason, no other changes are made to the winding layout or motor geometry, including
changes that would reduce the eddy effect. The resultant efficiency map has a
peak efficiency of only 90%, performing worse than the stranded wound motor across
most of its operating range. At very low speeds, under 1000 rpm, the efficiency of
the bar wound machine is better than that of the stranded machine. The bar wound
machine also has the advantage of being over 80% efficient everywhere. The author
suggests that future research focus on applying the proposed benchmarking algorithm
to stator bar motors designed to limit eddy effects. Strategies include changing the
slot opening shape, increasing the number of stator bars, and moving the stator bars
away from the air gap. / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/29564 |
| Date | January 2017 |
| Creators | Koke, Hannah |
| Contributors | Emadi, Ali, Mechanical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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