Technical Paper Wind power coupling with integrated safety brakes

Instead of simply offering a customer specified brake disk integrated to a coupling, Mayr Power Transmissions have taken the logical step of offering a complete modular system, drawing on their decades of experience with torque limiters, shaft couplings and electromagnetic safety brakes.

Although conventional hydraulic brakes can apply high brake torque, they are more prone to failure due to leaking callipers, damaged hoses and wear on the valves resulting in downtime and high maintenance and repair costs. Due to its high reliability, the Mayr ROBA®-diskstop electromagnetic brake, which has proven its worth in the safety critical elevator industry over many years, is a viable alternative for small and medium wind power installations.

Under normal conditions, the turbine rotor is slowed by feathering the pitch of the blades, reducing the rotor speed before engaging the brakes. On emergency stop, the brakes have to engage at full generator speed and absorb very high frictional work. To cope with this, Mayr have developed special sintered brake linings which offer high thermal stability, more reliable surface pressures and very low wear rates.

At the core of the module is the Patented ROBA®-DS coupling featuring an electrically isolating GRP intermediate sleeve which can be disassembled without moving the gearbox or generator radially. The coupling can accommodate up to 4º of misalignment and, using the latest computer modelling tools, the coupling’s torsional and compensation rigidity values can be optimised in line with customer / operational requirements at the design stage.

Overload protection is achieved by an integrated frictionally locked sleeve. The special friction material has been designed to maintain a stable and repeatable release torque exhibiting a tolerance of +/-15% over 1000 releases. For security, the overload module is calibrated during manufacture to prevent the possibility of adjustment errors during installation.

The whole wind power module is designed to be maintenance free over its entire service lifetime when used under normal turbine operating conditions. Where high friction work is encountered all that is required is periodic inspection and renewal of the brake linings.

Mayr Power Transmissions have extensive experience in providing bespoke solutions for both horizontal and vertical axis wind turbines – please see www.mayr.co.uk for product and contact details.