Wind Generator Slip Rings

Wind turbine operators running GE 1.5MW, 1.6MW, 1.7MW, and 1.85MW platforms know the challenge well: heavier loads, boosted operating conditions, and years of continuous in-field wear push the original slip ring system to its limits. 

As turbines age and output targets rise, the original stainless steel slip ring design - adequate at lower loads - becomes a liability rather than an asset. Mersen's wind turbine solutions team has engineered a direct answer: the SR 13-15 bronze slip ring assembly, built to outperform legacy stainless steel designs across every measurable metric, from operating temperature to brush life.

The case for bronze: why stainless steel falls short above 1.5 MW

Stainless steel slip rings have a well-documented failure pattern in wind applications: at loads above 1.5 MW, especially under extreme ambient temperatures or boosted operation, they generate excess heat, accelerate brush wear, and contribute to NDE (Non-Drive End) bearing temperature faults. The problem worsens as turbines are pushed toward higher output targets.

Bronze behaves fundamentally differently. The alloy is gentler on carbon brush contacts, dissipates heat across a wider surface area, and maintains consistent electrical conductivity under variable load conditions — precisely the demands of a modern wind generator running at boosted capacity.

Mersen has validated this advantage across thousands of real-world deployments. The SR 13-15 bronze slip ring, developed in collaboration with OEMs for the GE-Hitachi 1.X platform, delivers:

• temperature drop of 30-40% observed on slip ring, holders, and brushes in field conditions
• brush wear rates reduced by 30-40% based on field trials, extending service intervals significantly
• brush life exceeding four years, compared to significantly shorter cycles on stainless steel equivalents
• lower NDE bearing temperatures, reducing the risk of temperature-related bearing faults
• robust grounding, protecting sensitive WETA cards from electrical transients

Over 4,000 SR 13-15 bronze slip rings are now operating across the United States, making this one of the most widely deployed upgrade solutions in the US wind fleet. In 2017 alone to 3,000 turbines received Mersen's CG 677 carbon grade as part of this transition, with all units running successfully.

SR 13-15 slip ring: technical specifications and installation

The SR 13-15 is a retrofit upgrade designed for the GE-Hitachi 1.X generator platform, covering the 1.5MW, 1.6MW, 1.7MW, and 1.85MW variants. The design philosophy is plug-and-play: no modifications to the existing slip ring cabinet are required, and the unit installs with two bolts per brush holder position.

Key engineering improvements over the original design include:

• plug-and-play fit for GE-Hitachi 1.X generators: compatible with existing brush holders for generators, installs in two bolts per position
• structure and components redesigned for minimal resistivity, improving overall conductivity across the rotor circuit
• wider ring surface providing greater contact area for heat dissipation
• heavy-duty lugs and rods for secure, low-resistance rotor cable connections
• improved bolt-on terminal connection significantly enhances contact quality with rotor leads
• perpendicular torque design eliminates the risk of accidental internal damage during installation and operation
• built to withstand boosted operating conditions across all wind regimes, including cold-climate and high-humidity sites

For optimum system performance, Mersen recommends pairing the SR 13-15 with dedicated carbon brushes for wind generators: the HCH-30X grade for phase contacts and the HCH-4X1 for ground contacts. These grades are specifically developed for the current densities and peripheral speeds of the GE-Hitachi platform and complement the thermal advantages of the bronze ring.

Full wind generator slip ring range: 850 kW to 9 MW

The SR 13-15 addresses one of the most widely installed platforms in the US fleet, but Mersen's slip ring manufacturing capability covers the full range of wind generator applications, from smaller community turbines to offshore utility-scale machines.

Mersen designs and manufactures slip ring assemblies across the following specifications:

• moulded or machined ring construction, with machined rings available for high-speed applications up to 3,600 rpm
• diameter range: 170 to 360 mm
• voltage range: 220 to 3,000V AC
• insulation class H/F
• 3-phase design with integrated grounding ring available as standard option
• material selection across non-ferrous alloys, stainless steel, and copper alloys depending on application requirements
• plain or helically-grooved ring surfaces
• helical grooves improve self-cleaning and reduce brush bounce at higher operating speeds
• finished product compliance: dynamic balance testing and dielectric testing on every unit
• qualification to international standards: ISO 9001, IEC, NEMA, ASTM, SAE, DIN

All designs are developed in close collaboration with OEMs and can be customised to specific generator architectures. Five manufacturing plants across three continents support global lead times, and Mersen's engineering teams are available for on-site technical support. Repair and refurbishment of existing ring sets is also available for asset owners managing aging turbine fleets, as an economical alternative to full replacement.