Report on Hobbyking 40A ESC 4A UBEC 9261000003 / BC3530-14 brushless drive reported a set of measurements on a test on elements of a drive system which is the basis for one of my flying quads.
This article reports some interesting characteristics derived from the measurements.
Test configuration:
- Gemfan 11×4.7″ SF propeller;
- BC3530-14 1000Kv motor;
- Hobbyking 40A ESC 4A UBEC 9261000003 (BEMF caps removed);
- SimonK commit 02bd8e4ca36a06722efe51bc7cd5130d72a184b8 bs.hex with 2000ns dead time; and
- 4Ah 4S Lipo battery.
Keep in mind that the application for this drive is a multirotor, and hover speed is around 3800RPM, so efficiency in that region is critical to battery endurance.
Measured data
Derived data
Thrust vs RPM^2
A first approximation of thrust is that it is proportional to RPM squared.
Above is the measured data and a linear regression. The measured data is a fairly good fit to a straight line passing through the origin (ie linear with zero intercept).
Input power vs RPM^3
A first approximation of input power is that it is proportional to RPM cubed.
Above is the measured data and a linear regression. The measured data is a fairly good fit to a straight line passing through the origin (ie linear with zero intercept).
Input current vs RPM^2
Since the drive is powered from a constant voltage source for these tests, it is also the case that a first approximation of input current is that it is proportional to RPM cubed.
Above is the measured data and a linear regression. The measured data is a fairly good fit to a straight line passing through the origin (ie linear with zero intercept).
Efficiency
A first approximation of output power of a propeller is that it is proportional to RPM cubed.
Above is the calculated relative efficiency based on measured RPM,thrust and assuming a cubic relationship between speed and power.
Above is the drive efficiency calibrated to the propeller characteristic in DriveCalculatorv3.4.
Thrust factor g/W
A figure sometimes used to express performance of a drive is the ratio of thrust to input power expressed in g/W.
Above is the thrust factor calculated from the measurements.