Figure 7: Trapezoidal Construction - ST STM32 User Manual

UM2124
The rotor magnetic field produces a BEMF signal in the stator windings. If the motor is
intrinsically sinusoidal or trapezoidal, the induced BEMF signals are periodic and their
frequency is proportional to the frequency of the motor turns. The proportional coefficient is
the number of motor pole pairs; this number is used to calculate the mechanical speed of
the motor: for instance, with 1000 Hz and 10 pole pairs (or 20 poles) the mechanical
frequency is equal to 100 Hz.
The motor speed in rpm can consequently be calculated by measuring the electrical
frequency of the motor:
Equation 1
where, step
length of each step. It is multiplied by the number of steps and converted in rpm. The new
value of step
the frequency of the step generation (Step_N to Step_N+1).

Figure 7: Trapezoidal construction

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is the duration (in seconds) of a low frequency timer that regulates the
time
is managed by the zero crossing calculation function and it is updated at
time
DocID029868 Rev 1
Implementation of six-step motor control
algorithm in STM32 Nucleo microcontroller
60
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