AN1931D Freescale Semiconductor / Motorola, AN1931D Datasheet - Page 48

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

Implementation Notes
7.1.2 Current Scaling
Note:
48
where:
u
u
VOLT_RANGE_MAX Defined voltage range maximum used for scaling in physical units[V]
In the application, the VOLT_RANGE_MAX value is the maximum measurable DCBus voltage:
All application voltage variables are scaled in the same way (u_dc_bus, u_dc_bus_filt, u_SAlphaBeta,
u_SDQ, u_SAlphaBeta, and so on).
Current scaling also results from the sensing circuits of the hardware used; for details see 3-Phase
AC/BLDC High-Voltage Power Stage User’s Manual.
The relationship between real and fractional representation of current quantities is:
where:
i
i
CURR_RANGE_MAX Defined current range maximum used for scaling in physical units[A]
In the application, the CURR_RANGE_MAX value is the maximum measurable current:
All application current variables are scaled in the same way (components of i_Sabc_comp,
i_SAlphaBeta, i_SDQ, i_SDQ_desired, i_Sd_Alignment and so forth).
Frac
Real
Frac
Real
CURR_RANGE_MAX
VOLT_RANGE_MAX = 407 V
CURR_RANGE_MAX = 5.86 A
As shown in 3-Phase AC/BLDC High-Voltage Power Stage User’s Manual, the current
sensing circuit provides measurement of the current in the range from CURR_MIN = -2.93A
to CURR_MAX = +2.93A, giving the voltage for the ADC input ranges from 0 to 3.3V with
1.65V offset. The DSP5680x’s ADC converter is able to automatically cancel (subtract) the
offset. The fractional representation of the measured current is then in the range <-0.5, 0.5),
while the possible representation of a fractional value is <-1,1), as shown in
Therefore, CURR_RANGE_MAX is calculated according to the following equation:
Freescale Semiconductor, Inc.
Fractional representation of voltage quantities
Real voltage quantities in physical units
Fractional representation of current quantities
Real current quantities in physical units
3-Phase PM Synchronous Motor Vector Control
i
For More Information On This Product,
Frac
=
=
CURR_MAX-CURR_MIN
-------------------------------------------------------- -
CURR_RANGE_MAX
Go to: www.freescale.com
i
Real
=
2 CURR_MAX
(EQ
MOTOROLA
7-3.).
[-]
[V]
[-]
[A]
(EQ 7-7.)
(EQ 7-8.)