Controller design and technology-why not both sinewave and squarewave?

Electric Motors and Controllers
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kebekua   10 mW

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Controller design and technology-why not both sinewave and squarewave?

Post by kebekua » Jul 30 2018 10:42pm

Hi board,

I got a question for members who are versed in controller design and technology.

Squarewave controllers are more efficient at high speed. Sinewave must use field weakening to achieve the same speed with a given voltage and motor, and therefore are less efficient at high speed.

Why is it not possible to use sinewave at low speed, then switch to squarewave instead of using flux weakening?


Thanks in advance for your answers
''Power is not a means, it is an end.'' O'Brien, 1984

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Alan B   100 GW

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Re: Controller design and technology-why not both sinewave and squarewave?

Post by Alan B » Jul 31 2018 10:29am

Could do that, not clear it is useful. Square waves include harmonics that waste some energy, so efficiency is not optimized.

There are other techniques that may work better.

Using SVM (space vector modulation) sine wave drive you gain 15% speed (voltage) without field weakening.

https://www.electronicproducts.com/Elec ... ation.aspx

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Toorbough ULL-Zeveigh   10 MW

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Re: Controller design and technology-why not both sinewave and squarewave?

Post by Toorbough ULL-Zeveigh » Jul 31 2018 8:45pm

liveforphysics wrote:
Mar 25 2014 11:35pm
FalcoeMotors wrote: We use all three forms of excitation in our algorithm. Trap at startup and then sine with FOC.
That is awesome to hear.  Should enable ~5% more torque around startup at the cost of a tiny bit of efficiency and increased torque ripple (which would also be significantly less noticeable with 5p than 3p). Then cruise efficiency is unaffected by induced harmonic content from trap drive, but you still get the torque advantage when starting. Cool 
neptronix wrote:
Mar 25 2014 2:40pm
What are we paying $645-$745 more for? i think it's important to state the justification for the price premium.
Trapezoid Excitation: A five phase motor architecture can be driven with a trapezoid which covers full 180 degree electrical cycle whereas a three phase trapezoid can only cover 120 degrees.
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kebekua   10 mW

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Re: Controller design and technology-why not both sinewave and squarewave?

Post by kebekua » Aug 01 2018 10:07pm

thanks!
''Power is not a means, it is an end.'' O'Brien, 1984

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zro-1   1 kW

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Re: Controller design and technology-why not both sinewave and squarewave?

Post by zro-1 » Aug 01 2018 10:51pm

OK, dumb question: How does a FOC (field oriented controller) compare to what's been described above?
~01~

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Alan B   100 GW

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Re: Controller design and technology-why not both sinewave and squarewave?

Post by Alan B » Aug 02 2018 11:47am

FOC is one way to do Sinewave, it measures the voltages and currents and uses matrix calculations to find the position of the rotor precisely and control the currents in relation to its position.

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