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Originally Posted by nbalthaser
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also, i don't understand how you're defining "variable ratio" and "transmission". some would argue that psd isn't really even a transmission.
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Sorry abuot that, you're right, I meant power, and
elecrtical transmission from the sun generator to the ring motor (or vice versa).
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one challenge i see in trying to categorize psd as cvt is that at higher road speeds (lets say greater than 80mph), the motor/generator attached to the ring gear (mg2?) is going to need a remain stationary thus requiring more power from the ice at maybe 30% inefficiency. that means the ice is going to have to work harder to provide the power. this quirk gives me pause when considering psd a true cvt. obviously a belt and pulley cvt doesn't have this problem. so at lower speeds, psd appears to act like a traditional cvt but at higher highway speeds it starts acting less and less like one. i would imagine there is a speed limit where mpg drops precipitously b/c the ice is working so hard to overcome the inefficiencies of the mechanical->electrical->chemical->electrical->mechanical energy conversions.
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As far as I know there is not electrical->chemical->electrcal phase, unless power is being stored into the battery. Most of the time, it is simply transferred from one motor directly to the other without passing through the battery.
It is true that the system acts like a CVT at slower speeds, but runs into the problem of possibly over-revving the components at faster speeds. The solution to this would be to implement the ability to have a separate true gear. Some eCVT designs (which still go by the name elecrtic CVT) have multiple gears for this reason.