How to Select a Winding
If you have not already done so, the first step is to select a motor of
the correct size and performance category. See How
to Select a Motor.
The next step is to decide the number of turns in the winding. This
determines the rotational speed and adapts the motor to the task in hand.
Each motor can be precisely matched to an individual model application. It
is no longer necessary to make endless trial and error attempts with
different propellers and batteries in order to find the ideal drive
system. The information presented here provides a practical and reliable
reference for predicting flight performance.
One of the common terms used to compare electric motors is the voltage
constant which specifies the rpm produced by a motor per volt applied and
is generally denoted as ns (or Kv). This
makes it possible to calculate the number of turns n
at a given voltage U:
n = ns * U
Unfortunately, ns is dependent on the loading
of the motor, or the load current. It more or less sinks with the load
current. The rate at which the rotational speed decreases is denoted by
the term kns. This will be of greater
technical interest but is not used here.
In order to avoid complex calculations, each Torcman motor is represented
with ns for specific current values in line
with standard usage.
In the following tables some combinations have been deliberately removed
as they would make very little sense, for example TM280-05 with 30 cells
or TM430-30 operating on 8 cells, and only useful values remain.
Operating voltages are higher as the intended level of performance
increases. Small motors operate with 7-10 cells, the intermediate
performance categories 10-16 cells and the most powerful motors 16-32
cells.
Tables of measured ns values at specific
currents
A word about controllers
Only the brushless type controller can be used with these motors. The
purpose of a brushless controller is to produce 3-phase alternating
voltage from the DC voltage supplied by the battery. The commutation
software of these controllers and their timing (advancement of the
rotating electromagnetic field opposite the rotor), precisely determines
the rotational speed of the motor, its maximum current as well as its
starting characteristic. The same brushless motor can produce very
different rotational speeds with various controllers. If rotational speed
increases by a small amount there is a corresponding increase in current
drawn from the battery.
All values refer to measurements using a Jeti-Hacker
controller. With other controllers the rotational speeds must be
reduced accordingly:
Schulze, Kontronik -5%
Actronic, MGM, SPEEDY-BL -10%
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