synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
Wouldn't anything metallic, such as lock-nuts or flanges, bridge the gaps?
Non-ferrous locknuts as in Mike's graphic.
The slots are used to prevent a magnetic field induced by the current through an isolated phase conductor from circulating around it inside the ferrous metal sheet which has a high magnetic permeability (a measure of conductivity for magnetic fields). The slots prevent this circulating magnetic field by effectively creating a larger hole that surrounds all of the phase conductors, and so the conductor's magnetic fields within this larger hole will cancel out and therefore not have an effect.
Circulating magnetic fields induced in a ferrous metal will create hysteresis losses within that metal, as well as resistive losses from surrounding eddy currents, resulting in heating.
Metallic materials such as aluminum and zinc are good conductors of electrical currents, but not of magnetic fields like ferrous materials are. In fact, the magnetic permeability of aluminum and zinc is essentially the same as air, but that of steel is on the order of a thousand times higher. And so non-ferrous locknuts would not "short out" the magnetic fields between the sides of the slots, and so what infinity mentions about using them is correct.