In the area of “turbo gearboxes”, Kissling has received numerous queries for gearboxes with not only high speeds, but also high transmission ratios. New gearbox concepts were reassessed and developed, now resulting in the ASTRO gearbox series. This two-stage planetary gearbox is ideal for transmission ratios with values between 15:1 and 25:1. The ASTRO design is very appealing versus its traditional counterparts as it has been designed with compactness of construction in mind, along with extremely high efficiency.

High power density – FlexPin technology and torque split

The primary principle in the development is a very high degree of reliability, combined with very high efficiency. The result is definitely worth a look – the gearbox is compact, stable and low maintenance.

While the planet carrier of the input stage is connected directly with the output, it transfers approximately 30% of the torque. Meanwhile, the balance of the torque is transferred via the ring gear to the sun of the output stage to the output shaft via additional planets.

The planets run on bearing bushes that are fastened using FlexPins. The FlexPins ensure a constant distribution of the forces, even in the case of slight misalignment or non-uniform loading. The planets are supported by the planet spindles, which are held by the FlexPin.

The bearing can move under a load, thus compensating for the forces. With this design, the gearbox better compensates for angular and axial offset. Not only is the force variation optimized in the tooth, but the load is uniformly distributed on the planets. As a result, up to seven planets can be used on each stage, thereby greatly increasing the possible torque transmission per stage.

Utilization in biomass and fuel cell power stations

The ASTRO gearbox is typically applied between a gas turbine – with a power range up to 5MW – and a generator. These small gas turbines have high speeds that must be reduced to the generator speed.

Today, the main area of application of these gas turbines is in biomass and fuel cell power stations, as well as in traditional natural gas power stations. Small scale power stations that produce the required power locally are currently in vogue.

New projects with the ASTRO gearbox

With the ASTRO gearbox, Kissling is meeting market trends. In the first project, the ASTRO gearbox is utilized in a wood chip power station.

The novel process makes it possible to efficiently extract power and heat from waste wood. These combined heat and power generation plants are attractive for the wood processing industry. The newly constructed plant will go into operation in early 2009 and is scheduled to prove its capabilities throughout the winter.