|SinusLeistungsSteller - DC from battery|
DC from battery:
The Field Oriented Control (FOC) ensures the 3 motor phase currents to be sine-shaped and of equal amplitude. These motor currents establish a three-phase system with variable amplitude and frequency, with fixed shift of 120° between 2 motor currents.
The overlapping of these three motor currents, seen over one electrical period, effects a constant energy intake from the motor and thereby also a constant energy consumption from the battery - even in partial load situations!
Because nearly pure DC-current flows on the battery side (no superimposed AC current and no pulse-like currents as in block commutated ESCs), the cable length between battery and SLS is uncritical! This fact has been proven practically on a 70-meter-long DC-line with more than 1.5KW continuous power - of course in the controlled partial load!
So in all load situations DC-current is drawn from the battery. This also applies for currentsinto the battery - in other words: for situations in which the motor operates as a generator (e.g. active braking, wind energy, etc.).
In practice, this DC-current is superimposed with a slight AC component, which can be ignored. This superimposed AC component arises from inaccurate parameterization of the SLS or by non-linear effects that can not be controlled by the FOC.
The input capacitors (electrolytic capacitors) are loaded with less current ripple compared witch block commutated ESCs. Their lifetime is increased considerably.
A measurement in comparison with a block commutated ESC can be found HERE (ca.300 kByte)
For more details, please read HERE (ca.470 kByte)