Electric motorsport, probably more than any other genre of racing, is all about incremental gains, particularly in terms of powertrain development. Take Formula E, where even in the first season of competition efficiency of the spec McLaren supplied motor and inverter package was around 96 per cent, a fair figure today would be somewhere between 98-99 per cent efficient. But however small the improvements, across the board – be it in WEC, F1 or FE – manufacturers have been chasing electrical efficiency gains from motors, inverters and battery systems. It is the first of these that we will focus on here.
An electric powertrain must be considered in terms of the motor and controller when thinking of efficiency (and where used, the transmission). Each element is closely linked, and gains made in one area can easily be cancelled out if another part of the chain has excessive losses. Similarly, it is impossible to create a highly efficient motor without a suitably capable control system (just as an F1 engine would be useless without its ECUs).
To briefly recap the types of motor most found in racing applications, at one end of the scale are the very high output, but relatively crude DC units, like those found in electric drag cars. These have excellent power characteristics but are hard to control and not suitable for applications that require energy recovery. Advanced hybrid and electric race vehicles tend to use AC (alternating current) motors and amongst the various subsets of AC motors, synchronous motors are currently seen as the best solution. In most applications, this means the use of permanent magnet synchronous motors (PMSMs), of either the axial or radial flux type.
The majority of
