06. January 2020

Innovatice gear unit with electrical power splitting RENK chooses VEM as its partner for development of a special superimposition motor.

Where high-power drives are required to operate within a limited speed range and under particular ambient conditions, for example in explosive atmospheres, the speed superimposition of planetary gearing systems plays an important role. To date, this was generally realised by way of hydraulic couplings based on the Föttinger principle, in other words with hydromechanical torque converters. The hydraulic coupling controlled the power transmission and thus varied the drive output. Power which is removed from the main drive system in this way is naturally lost as far as the drive is concerned. With electrical superimposition, on the other hand, this problem is overcome by way of energy recovery via a converter.

Under the name RECOVAR®-E, RENK has now developed a gear unit which realises speed superimposition electrically - a solution which does away with the large quantities of oil required by a torque converter. As hydrodynamic drives are significantly inferior to their electric counterparts in terms of efficiency, RECOVAR®-E can point to a much higher degree of efficiency compared to the previous hydrodynamic technology. Planetary gearing between the high-power drive and the driven machine provides for the necessary transmission, e.g. to drive a compressor. A second motor, the so-called superimposition motor, takes care of speed variability.

For this superimposition motor, RENK opted for cooperation with VEM. The motor was designed as a low-voltage asynchronous motor with special slide bearings and water-jacket cooling, and is to be fully integrated into the overall solution. This superimposition motor operates as a motor in the principal direction of rotation and as a enerator when rotated in the opposite direction, and in doing so either increases or reduces the speed at the gear unit output relative to a basic speed. The VEM superimposition motor has already been tested successfully under full load and even exceeded all demands specified by the customers.

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