How should be the magnetic and electrical loadings in a highly efficient electric machine?

To achieve high efficiency in an electric machine, the design of both magnetic and electrical loadings must be optimized. Here is how these loadings should ideally be:

1. Optimal Magnetic Loading: Magnetic loading refers to the flux density in the core and air gap of the machine. For high efficiency:

– The machine should have high magnetic loading to reduce the size of the machine, which in turn reduces the amount of active material (like copper and iron) required. However, too high magnetic loading can increase core losses (hysteresis and eddy current losses).

– It’s crucial to find a balance where the magnetic saturation of the core is avoidable as it leads to an increase in exciting current and, consequently, higher excitation losses.

– An optimal level minimizes total core losses (both hysteresis and eddy current losses), keeping efficiency high.

2. Optimal Electrical Loading: Electrical loading, often referred to in terms of current density or ampere-turns per meter, should also be optimized:

– High electrical loading increases the output power for a given machine size but also increases resistive losses in the windings (I²R losses). Hence, a balance is necessary.

– Optimal electrical loading is chosen to keep copper losses to a minimum without excessively large conductors that would increase cost and reduce the space available for magnetic materials.

– Thermal considerations are paramount because increased losses require improved cooling systems, potentially reducing efficiency and increasing