ADMC200

REV. B

–8–

ρ

90

°

Stationary

Rotating

Reference Frame

Reference Frame

Figure 9. Forward Park Transformation

W

U

V

120

°

120

°

120

°

Equivalent

Three-Phase Stator

Two-Phase Voltage

Voltage

Figure 10. Forward Clarke Transformation

Operating/Using the Vector Transformation Block

After powering up the ADMC200,

RESET must be driven

low for a minimum of two clock cycles to enable vector

transformations.

The vector transformation block can perform either a forward or

reverse transformation.

Reverse Transformation is defined by the following operations:

(a) Clarke: 3-phase current signals to 2-phase current signals

followed by (b) Park: 2-phase current signals cross multiplied by

sin

ρ, cos ρ which effectively measures the current components

with respect to the rotor (stationary) where

ρ is the electrical

angle of the rotor field with respect to the stator windings.

Forward transformation is defined by the following operations:

(a) Park: 2-phase voltage signals cross multiplied by sin

ρ, cos ρ

followed by (b) Clarke: 2-phase to 3-phase voltage signal

conversion.

In order to provide maximum flexibility in the target system, the

ADMC200 operates in an asynchronous manner. This means

that the functional blocks (analog input, reverse transformation,

forward transformation and PWM timers) operate indepen-

dently of each other. The reverse and forward vector transfor-

mation operations cannot occur simultaneously. All vector

transformation registers, except for RHO/RHOP, are twos

complement. RHO/RHOP are unsigned ratios of 360

°. For ex-

ample, 45

Performing a Reverse Transformation

A reverse transformation is initiated by writing to the reverse

rotation angle register RHO and operates on the values in the

PHIP1, PHIP2 and PHIP3 registers. When the reverse trans-

formation is in 2/3 mode, PHIP1 is calculated from PHIP2 and

PHIP3. This is used in systems where only two phase currents

are measured. The reverse transformation 2/3 mode is set by

clearing Bit 10 in the SYSCTRL register and is the default

mode after

RESET.

In order to perform a reverse transformation, first write to the

PHIP2 and PHIP3 registers, and to the PHIP1 register if not in

2/3 mode. Then initiate the transformation by writing the re-

verse rotation angle to the RHO register.

The reverse rotation will be completed in 37 system clock cycles

after the rotation is initiated. If Bit 6 of the system control reg-

ister is set, then an interrupt will be generated on completion.

When an interrupt occurs, the user must check Bit 1 of the

SYSSTAT register to determine if the vector transformation

block was the source of the interrupt.

During the vector transformation, the vector transformation

registers must not be written to or the vector rotation results

will be invalid.

Reverse Clarke Transformation

The first operation is the Clarke transformation in which the

represent the equivalent currents in a two-phase ac machine and

is the signal format required for the Park rotation. The three-

phase input signals are of the form:

PHIP1

θ

PHIP2

θ + 120)

PHIP3

θ + 240)

θ and

This is calculated from:

IY

3

phase input current information.

In the case where 2 of 3-phase information (PHIP2/3 only) is

provided, then PHIP1 will be derived from the simple fact that

all sum to zero. This value is then placed in the IX register.

Reverse Park Rotation

IX/IY are then processed together with the digital angle

ρ

then the rotation can be described by:

ID

IQ

where ID and IQ are the outputs of the Park rotation.

Cos

ρ and sin ρ are required for the Park rotation, and are cal-

culated internally.

ID

IQ

Performing a Forward Transformation

In order to perform a forward rotation, write values to the VD

and VQ registers and then initiate the transformation by writing

the rotation angle to the register RHOP. The forward transfor-

mation will only operate correctly when Bit 10 in the

SYSCTRL register is set (i.e., in 3/3 mode).

The forward rotation will be completed in 40 system clock

cycles after the rotation is initiated. If Bit 6 of the system con-

trol register is set, then an interrupt will be generated on