Insulation parts
Turn Insulation for Air-Cooled Generator Rotors
Turn insulation separates the copper turns in a generator rotor and guides the cooling air through slots.
In the rotor of an air-cooled turbogenerator the copper conductors of a coil are stacked in the slot. Between each turn sits a turn insulation strip that prevents electrical contact between the conductors. Cooling air flows through openings in the copper conductors, and the turn insulation must leave these openings free. That is why our turn insulation strips carry elongated slots that match the ventilation geometry of the rotor exactly.
The expansion of renewable energy, rising electricity demand and grid stabilisation increase the demand for turbogenerators. Alongside new units, the overhaul of existing generators is growing strongly, because a rewound rotor is more economical than a new build. We supply turn insulation for both cases: as spare parts for the overhaul of a single generator and in series for OEM production.
Typical strip widths are 30 to 60 mm, material thickness 0.1 to 0.3 mm and length 2 to 5 metres. The combination of length, tight tolerances on pitch and slot position and the required repeatability across the whole winding makes this a demanding part. Our production is designed for exactly that.
Slot geometry to customer drawing
We manufacture to your drawing. Straight slots, staggered arrangements, varying pitches and customer-specific edge distances are implemented precisely. Several slot geometries on one strip are possible, as are special shapes at the ends. The tools are made in our own tool shop and can usually be realised at low cost, even for the small quantities of an overhaul.
The slot position stays accurate along the entire strip. This matters because a displaced opening throttles the cooling air flow and raises the local temperature in the rotor.
Materials for electrical, thermal and mechanical requirements
We select the insulation material together with you according to voltage stress, operating temperature and mechanical load. Impregnated glass fabrics, so-called prepregs, are used frequently because they bond firmly with the conductor when the coil is cured. Alternatively we process Kapton polyimide film, Nomex aramid paper or Nomex composites such as NKN laminate. We advise you on material selection.
Manufacturing at Hauler & Hermann
Long formats have been part of our core business for decades, we produce profiles and strips up to 20 metres in length. Turn insulation is made on our own punching and cutting lines with tools from the in-house tool shop. The result is high dimensional accuracy, repeatability across the whole series and short lead times even for complex geometries. Production is certified to DIN EN ISO 9001 and DIN EN ISO 14001.
Our capacity ranges from a single set for an overhaul to series supply for generator manufacturers. To match the turn insulation we supply slot wedges and further insulation parts for generator construction from a single source.
Selection criteria for purchasing and design
For a quotation we need the drawing with strip width, length, slot geometry and pitch, the required thermal class or preferred material, and the quantity per rotor and per year. For overhauls a sample part from the dismantled rotor is often enough, we then take the geometry ourselves. Lead time for a spare part set is about four weeks, depending on material procurement. Send us your enquiry via the contact form.
Product view
Production drawing of a customer part: 3,500 mm long, 33 mm wide, 40 cooling slots, position tolerance 0.5 mm
Frequently asked questions
What is turn insulation in a turbogenerator?
Turn insulation sits in the rotor between the stacked copper turns of a coil and prevents electrical contact between the conductors. In air-cooled rotors it carries elongated slots so that cooling air can flow through the winding.
Why do the strips have elongated slots?
The copper conductors of air-cooled rotors have ventilation openings. The slots in the turn insulation lie exactly over them and let the cooling air pass. If the slots are misaligned, the air flow is throttled and the rotor runs locally hotter.
Which materials are available?
Frequently impregnated glass fabrics (prepreg), which bond firmly with the coil during curing. Alternatively Kapton, Nomex or Nomex composites such as NKN. The choice depends on voltage, temperature and mechanical load.
Does Hauler & Hermann supply single sets for overhauls?
Yes. We produce spare part sets for the overhaul of individual generators as well as series for OEMs. Tooling costs remain moderate even for small quantities.
Which dimensions are typical?
Strip widths of 30 to 60 mm, material thickness of 0.1 to 0.3 mm and lengths of 2 to 5 metres. Our production handles long formats up to 20 metres, with the slot position staying accurate along the entire length.
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Talk to us. We will find the right insulation solution.