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# Vector Motors Clarke and Park Transformation

Vector motors is there any simple explanation of the math of Clarke and Park Transformation.

#1

09-16-2013 11:43 AM

Top #2

http://www.ti.com/lit/an/bpra048/bpra048.pdf

09-16-2013 02:14 PM

Top #3

Hi Thomas,

Clarke and Park Transformation are "simply" matrix of transforation to convert a system from one base to an other one:

- Clarke transform a three phase system into a two phase system in a stationnary frame.

-Then Park transform a two phase system from a stationnary frame to a rotating frame.

The Beauty of these transformations is after doing it, it simplifies a lot the math and calculation power to control the three phase motor (torque control, speed control, field weakening)

That's my two cents!

Jamal

Clarke and Park Transformation are "simply" matrix of transforation to convert a system from one base to an other one:

- Clarke transform a three phase system into a two phase system in a stationnary frame.

-Then Park transform a two phase system from a stationnary frame to a rotating frame.

The Beauty of these transformations is after doing it, it simplifies a lot the math and calculation power to control the three phase motor (torque control, speed control, field weakening)

That's my two cents!

Jamal

09-16-2013 04:27 PM

Top #4

Hi Thomas,

Please see the following link. http://focus.ti.com/docs/training/catalog/events/event.jhtml?sku=OLT210201.

It is a motor controls compendium by Texas Instruments. Page 42 of the pdf is the Clark transform. The powerpoint version should have the animations.

Best Regards,

Sandun

Please see the following link. http://focus.ti.com/docs/training/catalog/events/event.jhtml?sku=OLT210201.

It is a motor controls compendium by Texas Instruments. Page 42 of the pdf is the Clark transform. The powerpoint version should have the animations.

Best Regards,

Sandun

09-16-2013 07:14 PM

Top #5

Microchip AN957 is another great document. Basically its just geometric conversion math processing fro 3 phase to 2 phase rotating frame and back again.

09-16-2013 09:28 PM

Top #6

Just to add a little trick I have to gain insight into the system. Under certain conditions (such as balanced voltages or currents, and no harmonics) you can get away with describing a three-phase system using only two pieces of information. You can us your knowledge of two phases to infer the third, provided the power system is clean and balanced. This is similar to when you have a power meter, and you only need two CT's or VT's to infer the behaviour of the third phase.

It then follows that you can choose which two vectors to describe the three phase behaviour, which can be represented by a Y that rotates 360 degrees for every cycle of mains power (each line is a phase). The two axis representation will look like an x-y axis superimposed on this rotating Y in the chart. One are to have an x-y axis where the x is stuck to phase A (Park) or another one is to have all three phases move around while the x-y axis remains stationary (Clarke), as described above.

It then follows that you can choose which two vectors to describe the three phase behaviour, which can be represented by a Y that rotates 360 degrees for every cycle of mains power (each line is a phase). The two axis representation will look like an x-y axis superimposed on this rotating Y in the chart. One are to have an x-y axis where the x is stuck to phase A (Park) or another one is to have all three phases move around while the x-y axis remains stationary (Clarke), as described above.

09-17-2013 12:16 AM

Top #7

The transformations afford better mathematical tractability and provide more intuitive insight into the operation of rotating electrical machines. Clarke's transformation reduces a a multi-phase system of an arbitrary number of phases to an equivalent two-phase system (in quadrature) plus a zero-sequence component that, in the balanced case remains zero and may be neglected. Currents, voltages and fluxes may be described then in a two-axis orthogonal coordinate system as vectors (such as in an X-Y plane) whose lengths describe the magnitude of that quantity. The vectors can be be viewed as rotating at fundamental frequency, but may have relative phase displacement among them. Park's transformation may most easily be described as a change in perspective: rather than describing the aforementioned vectors as rotating in a fixed coordinate system, such as one that may be viewed as fixed to the stator (e.g. of a synchronous machine) where the electrical quantities are time-varying even in the steady-state, we can instead rotate the coordinate axes at synchronous or slip speed such that the coordinate axes are instead affixed to the rotor. In this way, the vectors are seen as stationary in the steady-state with some arbitrary phase displacement among them. This is the intent of the Park transformation.

09-17-2013 04:44 AM

Top #8

If you want to skip the maths of vector control entirely and get a different perspective as to what is actually hapening in an induction machine, then a paper my old uni published is well worth looking at:

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=488215&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F2194%2F10515%2F00488215.pdf%3Farnumber%3D488215

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=488215&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F2194%2F10515%2F00488215.pdf%3Farnumber%3D488215

09-17-2013 07:22 AM

Top #9

Is there a way to get the IEEE paper without paying?

09-17-2013 09:47 AM

Top #10

The articles about Clark's and Park's transformation were very useful, Thank you!

09-17-2013 12:27 PM

Top #11

@Brad - the paper is actually an IET paper and I see you can get it from them for £15 but still not free. Sorry I think you would have to pay for it.

09-17-2013 03:15 PM

Top #12

Try the following books (only authors listed, forgot titles):

(1) Novotny & Lipo

(2) Krause

(3) Trydznalowski (spelling?)

(4) B.K. Bose

(1) Novotny & Lipo

(2) Krause

(3) Trydznalowski (spelling?)

(4) B.K. Bose

09-17-2013 05:25 PM

Top #13

Follow this link, to a video from Texas Instruments, for a thorough explanation of Field Oriented Control and Clarke/Park:

http://www.youtube.com/watch?v=cdiZUszYLiA

http://www.youtube.com/watch?v=cdiZUszYLiA

09-17-2013 08:06 PM

Top #14

Valuable responses have been provided but the word DC has not been mentioned. Which provides opportunity to present a historical slant especially on the the Park transformation which is arguably by far the single most important concept needed for an understanding of high-performance vector-controlled AC drives. The Park transformation was first conceptualized in a 1929 paper authored by Robert Park. Park's paper was recently ranked 2nd most important paper ever written in 20th century in terms of power engineering impact. The novelty of Park's work was in his ability to transform any related machine's linear differential equation set from one with time varying coefficients to another set with time invariant coefficients. Most importantly, through the Park transformation, a vector-controlled AC drive allows a three-phase induction motor to behavior like a separated-excited DC motor with torque control decoupled from flux control.

09-17-2013 11:03 PM

Top #15

Thanks to everyone and all responses. I am still bringing it all in,.