Laminated transformerwood dielectric data must retain field direction, electrodes and original units. Match those test paths to the part’s intended electrical duty before comparing material results. [1]
Calculation basis. Project-specific values and gates in the illustrative screens below are assumptions; cited catalogue values retain their source test conditions.
Define the electric-field direction relative to the layer plane separately from the grain directions within the veneers. “Along the wood” is insufficient for a cross-laminated part.
Draw the two test paths
| Test direction | Electrode-path definition | Construction encountered |
|---|---|---|
| Across the lamination | Electrodes arranged to drive field through the identified thickness | Successive veneer and bond regions along the path |
| Along the lamination | Electrode spacing and orientation within the specified plane | Veneer directions and nearby interfaces in that plane |
| Surface or edge exposure | Accessible oil/solid interface and electrode edge geometry | Machined surface, protrusions and possible surface failure path |
Preserve specimen dimensions, electrode geometry, waveform, oil state and temperature with the result. A manufacturer sheet that reports field strength in one direction and voltage over a stated path in another is not offering two directly equivalent local fields.
Dividing a test voltage by a path length yields a nominal average. It does not reconstruct the maximum field near the electrodes or prove that the two arrangements have the same stress distribution. The result must remain associated with its test method.
Identify the failure that the test actually produced
Observe whether the event occurred through the intended material volume, along an exposed interface or around an electrode edge. A surface or edge event may limit the test before the intended bulk path is demonstrated. Its location is part of the evidence, not merely a reason to discard an inconvenient result.
Use electrode and specimen preparation appropriate to the selected qualified method. Machining damage and oil condition need control where they enter the intended path. A coupon with untouched stock faces may not represent a support whose most stressed region is a milled edge.
Field modelling can help compare arrangements using their material boundaries and potential conditions. It does not supply a breakdown or discharge threshold. For long-duration conditions, conductivity and charge distribution may also matter; a stationary dielectric contour does not automatically cover every test waveform.
Keep direction-specific results in separate specification entries. State which field path each supports and what conditioning applies. If the assembled part places the critical field at an oblique angle or near a metal insert, assess that geometry rather than selecting the larger datasheet number.
For a material substitution, require the relevant test direction and state to be reproduced or otherwise justified. Matching thickness and a general electrical-insulation label leaves the layer path, surface condition and electrode evidence unresolved.
The purchasing decision should rest on applicable tests for the intended field direction, with the original units preserved. That prevents a seemingly stronger material from being selected on the basis of an incompatible reporting convention.
Keep dielectric direction and test length with the result
Keep the densified-wood test direction and reporting path on the material requirement [2].
Röchling reports 17 kV/mm perpendicular to the lamination and 80 kV over a 25 mm parallel path at 90 °C under oil [1]. The latter is arithmetically 3.2 kV/mm, but the directions and test paths differ. Preserve the original quantities on the material record; obtain the relevant direction and geometry before applying either result to a finished support.
References
- Röchling Industrial, Lignostone L I/2-E3-HQ (P2R), Technical Data Sheet, version 2.0, released 20 September 2023.
- IEC, IEC 61061-2:1992, Specification for non-impregnated, densified laminated wood for electrical purposes — Part 2: Methods of test.