Quote:
Originally Posted by sanddrag
I'm confused by the above poster's method of adding ratios of speed and torque. Why does that work?
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See attached speed vs torque drawing.
E is the desired operating point with speed C and torque D
Line AB is the 12V speed vs torque curve (given)
If we can find G, then the "mystery" voltage is 12*(G/A).
Proceed as follows:
From similar triangles, (G-C)/D = A/B
Multiply both sides by D/A to get (G-C)/A = D/B
Expand the left side to get G/A - C/A = D/B
Move C/A to the other side to get G/A = C/A + D/B
So V = 12*(G/A) = 12*(C/A + D/B) which is what Aren did.
Of course, this ignores the 2.7 amp free current. What role should that play in this analysis?