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Core Losses in Electrical Machines

20 March 2021

Hub Director Professor Geraint Jewell presented the second FEMM Hub training session of 2021 on 18 March.

Professor Jewell led 98 delegates through his three hour training session on iron loss in electrical machines which took place via WebEx. Delegates, belonging to members of our academic and industry partners joined from across the globe.

An explanation of core stack build
Core stack BuildA number of different approaches taken in different sectors or machine sizes.Tend to sequentially index the laminations around when building up stack (if geometry features allow) to even out the 'rolling' and 'transverse' magnetic properties.Adhesive bonding coming to the fore in many applications:
  • Good dimensional control
  • Joins across full cross-section
  • Thermal cycling and long-term stability is a consideration
Good review of methods and arising performance issues in [XIA20].Welding can lead to localised heating even when done well.Note: No welds on inner edge - would form a closed loop for a large (and probably destructive) circulating current. Right: Examples of welded stacks, adhesive bonding and interlocking.Source: Xia et al. [XIA20]

Iron losses are a critical factor in determining the power density limits and efficiency of electrical machines, in particular with the inexorable growth in demand for electrical machines operating at higher speeds and driven from variable frequency power converters. The training course presented a comprehensive review of several aspects of iron losses in electrical machines. 

It included discussion of material properties, underlying loss mechanisms and aspects of electromagnetics, but the principal focus was on the impact of material selection, machine design, core manufacture and operating conditions. A significant proportion of the course was an introductory and general level with no pre-requisites assumed in terms of specific electrical machine knowledge. 

As such, it provided a useful introduction for material scientists and engineers drawn from a wide range of disciplines who wish to open the box and peek into the many mysteries of iron loss.