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SVTPerformance's Chain of Restaurants
Pics and Videos Buffet
Bought a Taycan Turbo S
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<blockquote data-quote="JPKII" data-source="post: 16825121" data-attributes="member: 12867"><p>The Porsche uses a permanently excited synchronous motor. So they vary speed by adjusting frequency applied to the stator windings. The rotor, or rotating portion of the motor, uses the fixed permanent magnets. Very good design and very expensive to produce.</p><p></p><p>The Variable Frequency Drive used to vary the stator frequency has a maximum theoretical limit at how quickly it can gate it's power devices (probably an IGBT or IGCT). The VFD has a maximum practical frequency it can produce.</p><p></p><p>Oversimplification: the motor's speed is proportional to frequency applied to the stator. Synchronous RPM == (Frequency * 60 * 2) / number of poles in the motor</p><p></p><p>Without getting into Vector control theory, the speed of the motor is physically limited by frequency applied to it. This is what will alway set the speed limiter in an EV. Increasing the speed (frequency), or over-modulation, means increasing the limits within the VFD but that comes at a loss of efficiency, increased heating, and reduction of reliability of the power device. IGBTs and IGCTs have a finite number of times they can reliably turn on and off.</p><p></p><p>In industrial applications where over-modulation is required, that usually comes with a de-rating factor for the VFD. So we up-size the VFD to compensate. Or better still, adjust motor/system dynamics so that over-modulation isn't required. </p><p></p><p>So we need to hack the VFD in the Porsche to over-modulate it to get higher speeds. Then sell it quick before the damn thing blows up.</p></blockquote><p></p>
[QUOTE="JPKII, post: 16825121, member: 12867"] The Porsche uses a permanently excited synchronous motor. So they vary speed by adjusting frequency applied to the stator windings. The rotor, or rotating portion of the motor, uses the fixed permanent magnets. Very good design and very expensive to produce. The Variable Frequency Drive used to vary the stator frequency has a maximum theoretical limit at how quickly it can gate it's power devices (probably an IGBT or IGCT). The VFD has a maximum practical frequency it can produce. Oversimplification: the motor's speed is proportional to frequency applied to the stator. Synchronous RPM == (Frequency * 60 * 2) / number of poles in the motor Without getting into Vector control theory, the speed of the motor is physically limited by frequency applied to it. This is what will alway set the speed limiter in an EV. Increasing the speed (frequency), or over-modulation, means increasing the limits within the VFD but that comes at a loss of efficiency, increased heating, and reduction of reliability of the power device. IGBTs and IGCTs have a finite number of times they can reliably turn on and off. In industrial applications where over-modulation is required, that usually comes with a de-rating factor for the VFD. So we up-size the VFD to compensate. Or better still, adjust motor/system dynamics so that over-modulation isn't required. So we need to hack the VFD in the Porsche to over-modulate it to get higher speeds. Then sell it quick before the damn thing blows up. [/QUOTE]
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Bought a Taycan Turbo S
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