AN1931D Freescale Semiconductor / Motorola, AN1931D Datasheet - Page 47

• Manufacturer Part Number: AN1931D
• Description: 3-Phase PM Synchronous Motor Vector Control
• Manufacturer: Freescale Semiconductor / Motorola

MOTOROLA
7.1.1 Voltage Scaling
The following equation shows the relationship between the real and fractional representations:
where:
Fractional Value is the fractional representation of the real value [Frac16]
Real Value is the real value of the quantity [V, A, RPM, etc.]
Real Quantity Range Max is the maximum of the quantity range, defined in the application [V, A,
RPM, etc.]
The C language standard does not have any fractional variable type defined. Therefore, fractional
operations are provided by CodeWarrior intrinsics functions (e.g. mult_r() ). As a substitution for the
fractional type variables, the application uses types Frac16 and Frac32. These are in fact defined as
integer 16-bit signed variables and integer 32-bit signed variables. The difference between Frac16 and
pure integer variables is that Frac16 and Frac32 declared variables should only be used with fractional
operations (intrinsics functions).
A recalculation from real to a fractional form and Frac16, Frac32 value is made with the following
equations:
for Frac16 16-bit signed value and:
for Frac32 32-bit signed value.
Fractional form, a conversion from Fraction Value to Frac16 and Frac32 Value can be provided by the
C language macro.
Voltage scaling results from the sensing circuits of the hardware used; for details see the 3-Phase
AC/BLDC High-Voltage Power Stage User’s Manual.
Voltage quantities are scaled to the maximum measurable voltage, which is dependent on the
hardware. The relationship between real and fractional representations of voltage quantities is:
Frac16 Value
Frac32 Value
Fractional Value
Fractional Value
Freescale Semiconductor, Inc.
3-Phase PM Synchronous Motor Vector Control
u
Frac
For More Information On This Product,
=
=
=
32768
2
------------------------------------------------------- -
VOLT_RANGE_MAX
Go to: www.freescale.com
=
=
31
--------------------------------------------------------------
Real Quantity Range Max
--------------------------------------------------------------
Real Quantity Range Max
--------------------------------------------------------------
Real Quantity Range Max
--------------------------------------------------------------
Real Quantity Range Max
u
Real
Real Value
Real Value
Real Value
Real Value
Implementation Notes
(EQ 7-2.)
(EQ 7-3.)
(EQ 7-4.)
(EQ 7-5.)
(EQ 7-6.)
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