The Power You Need, When You Need It. Government vehicles, transit buses and commercial vehicles share a common alternator problem – namely that a belt-driven alternator doesn’t make rated electric power during engine idling. This is because, at idle, the alternator speed falls below its rated speed. Sizing the pulley ratio to spin the alternator faster (beyond rated speed) at idle may cause the alternator to over-speed and fail.
A NuVinci® DeltaSeries™ alternator drive improves alternator performance by decoupling the engine speed from the alternator speed, enabling the alternator to operate in its optimal range based on demand regardless of engine speed. As a result, the NuVinci alternator drive delivers the ideal alternator speed all the time – providing needed power regardless of engine speed, reducing speed when power is not needed, thereby improving fuel economy. NuVinci CVP Technology At the heart of every NuVinci accessory drive is Fallbrook’s award-winning NuVinci continuously variable planetary (CVP) transmission technology.  The NuVinci CVP is a new class of CVT transmission technology that acts as a power management system to control the speed and optimize the performance of any engine accessory.  Unlike conventional CVTs, the NuVinci CVP uses a set of rotating and tilting balls positioned between the input and output components of the transmission that tilt to vary the speed of the transmission.  Tilting the balls changes their contact diameters and varies the speed ratio.  As a result, the NuVinci CVP offers a seamless and continuous transition to any ratio within its range. NuVinci DeltaSeries Alternator Drives Enable: Alternators to produce rated current regardless of engine RPM Optimally size the alternator for application / need Reduced failure rate of conventional alternator Improved system efficiency and increased fuel economy Improved battery life;  total energy from the alternator is dramatically increased (testing shows >750% additional energy generated during a typical workday)
NuVinci® Alternator Drive Model: 43CVP-A01 U-Drive Now Available for Beta Fleet Tests. See Specification Sheet (PDF).

Power at Idle

A NuVinci-based alternator drive improves alternator power at low engine speeds, with minimal complexity, easy installation and low cost.  The diagram below illustrates the NuVinci  CVP’s “U” drive power path configuration.  Power comes in from the belt, is transferred to one traction ring, through the planet balls, and out of the other traction ring.  Tilting the balls provides a smooth ratio transition from overdrive, providing high alternator speeds at low engine speeds, to underdrive, when the alternator might be operated at slower speeds.

The NuVinci CVP enables control of output speed (see red line in the chart below), independent of engine speed (the grey line).  At engine idle, output speeds may be increased, providing more power to the alternator.  At higher engine speeds (such as accelerating from a stop or cruising), accessory speeds may be reduced, saving energy.  The NuVinci CVP also shifts quickly, helping to smooth out transients.

The Result

The graph below illustrates the improvements in alternator performance possible with a NuVinci-equipped alternator.  A typical-high performance alternator (grey curve) does not provide full power at low engine speeds (less than 1,200RPM).  A NuVinci-equipped alternator (red curve) enables optimal alternator operation, even at low engine speeds.  The green area represents the increase in alternator current generated at low RPM, as compared to a standard alternator.  During idle, this can result in 50-100% more delivered power, depending on the alternator.

Click here for a NuVinci DeltaSeries Alternator Drive datasheet (PDF) (contents of this page in printer format)

Click here to read the NuVinci Development Briefing:  A Continuously Variable Accessory Drive for Alternators and Other Engine-Driven Accessories

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