Environmental Engineering Reference
In-Depth Information
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Figure 2.21 Acceleration performance of power split 'electric CVT'
For the stated conditions, and for
k
ΒΌ
2.8, the S/A speed remains positive and
governed by (2.2) for the given ring gear (vehicle) and carrier (engine) speeds. For
this particular choice of engine speed, both the S/A and M/G operate with positive
speeds and in generally efficient torque-speed regions. If the engine speed were
reduced somewhat during this acceleration event, the sun gear speed would actually
decrease to zero and reverse direction. Figure 2.22 illustrates this behaviour.
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Figure 2.22 Acceleration of power split transmission when engine speed is
lowered
Depending on choice of planetary and final drive ratios it is possible for the
power split S/A to assume inefficient operating points, particularly if its speed were
to dwell near the zero crossing point. This could be caused, for example, by poor
