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Voith Turbo: Power Distribution Gear Unit
Ideal for high performance and high speed
The power distribution gear unit by Voith Turbo BHS Getriebe is the modern answer to increased demand for high power density
gear units capable of transmitting high power at high rotational speeds. By combining the load distribution principle of
epicyclic gears with the simplified design of a parallel shaft gear, operating efficiencies of 99% are possible.
At first glance, the construction of the BHS power distribution gear is very similar to that of a standard epicyclic gear:
Three planet gears are arrayed around a central sun pinion. However, each planet gear is actually a compound design which
meshes with two sun pinion shafts: one input shaft and one output shaft. This design enables the power distribution gear to
act as a two-stage parallel shaft gear, but without high speed bearings and with a coaxial input and output shaft
arrangement. Since power is distributed over three two-stage planet gears without need for a ring gear, the overall gearbox
size is quite compact. In addition, the three planet gears are supported by six bearings instead of four (as in parallel
shaft gear units), which means bearing diameters and journal velocities are reduced compared to a parallel shaft unit of the
same power and speed transmission, while load capacity is increased.
Due to this load distribution feature, which segments the load into several smaller components, the BHS power distribution
gear unit is the ideal solution for high power, high speed applications. Gas turbine driven compressors provide a classic
example. Comparative calculations show the superiority of the power distribution gear unit as opposed to parallel shaft gear
units (see table). For a typical gas turbine to compressor application with speeds of
5 000/12 500 rpm, the maximum transmitted power of the parallel shaft gear unit is limited to 26 MW, because speeds cannot be
increased at the bearings or the toothing. Within this range, efficiency is only 98.1% for the parallel shaft gear unit,
compared to 98.8% for a power distribution gear unit. The power distribution gear in this example is able to transmit up to 65 Megawatts of power without losing any efficiency.
The load distribution principle allows optimization of rotating components while staying well within accepted limits,
reducing centrifugal forces and material stresses compared to parallel shaft gears. This also has a positive effect on the
service life and the operating safety of the components in the turbo gear unit.
Comparison of parallel shaft gear units and power distribution gear units
Example: application of gas turbine (5 000 rpm) to centrifugal compressor (12 500 rpm)
Highlight: integrated TwinTors double diaphragm couplings
Another feature of the power distribution gear unit is the integrated BHS TwinTors double diaphragm coupling, which ensures
an ideal power transmission connection between driver and driven machine. Both the high and low speed sides of the gear unit
include such a coupling. The integration of these couplings into the gear unit turns the BHS power
distribution gear into an axially compact unit, popular among customers for its space saving advantages. Axial, radial, and angular offsets in the
train are reliably compensated by the patented double diaphragm coupling. This design permits optimum load distribution
within the gear unit, enabling BHS to deliver a rotordynamically optimized system consisting of both gear unit and connecting
couplings.
Ease of maintenance also played a role in the development of this power distribution gear unit. The split casing, for
example, provides ready access for inspection and maintenance work. BHS delivers power distribution gear units with up to
170 MW power (3 600 to 3 000 rpm) or rotational speeds of up to 80 000 rpm. The power distribution gear unit is ideally
suited for applications outside the range of technical feasibility of parallel shaft and epicyclic gear units.
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Voith Turbo BHS Getriebe GmbH is part of the Voith Group and has been developing, from its location in Sonthofen, Germany,
the highest quality and technically mature level of gear units, couplings, and rotor turning gears for more than 75 years.
Currently, more than 20 000 gear unit references and a transmitted total load of more than
70 000 MW are documented in the reference lists.
Voith Turbo, the specialist for hydrodynamic drive, coupling and braking systems for road, rail and industrial applications,
as well as for ship propulsion systems, is a Group Division of Voith GmbH.
Voith sets standards in the markets energy, oil & gas, paper, raw materials and transportation & automotive. Founded in 1867,
Voith employs almost 40 000 people, generates €5.2 billion in sales, operates in about 50 countries around the world and is today one of the biggest family-owned companies in Europe.
www.voithturbo.com
www.bhs-getriebe.de
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For more information, media details or
sample copies please contact
wilhelms@pennwell.com
www.sicking.de
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