A varnish carrying a temperature index of 155 has not been run at 155 °C for its service life and survived. Nobody has that much time. (The type number and the temperature index are related but not the same thing — more on that below.) What has happened is this: specimens were aged at a set of elevated… Read More: Temperature Index of Insulating Varnish: What the Number Means »
ASTM D495 says it plainly in its own referenced-documents clause: IEC 61621 is technically equivalent to D495 and was built directly from it. That sentence gets quoted a lot, usually to justify treating a number from one as a number from the other. It does not mean that. “Technically equivalent” describes the method. It does not make the… Read More: IEC 61621 vs ASTM D495: What Actually Differs »
IEC 60034-27-3 is the standard that governs dielectric dissipation factor — tan δ — measurement on the stator winding insulation of rotating machines. This is a section-by-section walk through the document, in the order the standard itself uses, so you can find and understand any clause quickly. For the test in practice rather than the document structure, start… Read More: IEC 60034-27-3 Explained: Clause-by-Clause Guide »
Before IEC 60034-27-3, dissipation factor limits for stator insulation were mostly private — each manufacturer and utility worked to its own internal numbers. The standard put a public set on the table. That was useful, and it was immediately controversial, because a single set of numbers has to cover insulation systems that behave quite differently. So the limits… Read More: IEC 60034-27-3 Limits: tan δ Acceptance Criteria »
A bare CTI number can be read wrong. “CTI 400” looks like a clean result until you learn it was run with the aggressive contaminant, or that the 100-drop figure sat 50 V lower, or that erosion ate 3 mm off the specimen while it passed. All of that lives in the report — and a compliant report… Read More: How to Read a CTI and Tracking Test Report »
The letter stamped on a motor nameplate — usually F, sometimes B or H — controls how long that motor will last. Get the class wrong for the application and the motor either fails early or you paid for capability you’ll never use. Get it right and you have a motor engineered to run its full design life… Read More: Motor Insulation Class Explained: Class A, B, F, H —… »
The specimen decides the number almost as much as the material does. A tracking test measures how a surface behaves under a contaminated film, and nearly every rule about how you cut, clean, and condition that surface exists to stop the specimen itself from becoming the variable. Get the prep wrong and the result is not slightly off… Read More: CTI Test Specimen Preparation Guide (IEC 60112 & 60587) »
A datasheet quotes “CTI 400V, PLC 1, Material Group II” and an engineer new to the part assumes those are three separate properties. They are not. They are one measurement — surface tracking resistance — expressed in three different bookkeeping systems, because three different bodies standardized the same drop test. Knowing which system a number came from matters,… Read More: IEC 60112 vs ASTM D3638 vs UL 746A: CTI Standards »
The single most important thing to know before you use any CTI table: the number belongs to a grade, not a material family. Two compounds both labeled “PBT” can sit in different material groups because one has a flame-retardant package and a filler tuned for tracking and the other does not. Every value below is indicative — a… Read More: CTI Values of Common Insulating Plastics (with Table) »
IEC 60076-3 is the IEC standard that sets the insulation levels, dielectric tests, and minimum external air clearances for power transformers. It defines eleven dielectric tests, assigns each one as routine, type, or special based on the highest voltage for equipment (Um), and gives the test voltage tables. The current form is IEC 60076-3:2013 as amended by A1:2018.… Read More: IEC 60076-3 Explained: Dielectric Tests and Clearances »