IEC 60464-1 designates a varnish on three separate axes: what it is for, what resin it is built on, and what carries it. That third axis is the one that concerns us: Type Code Organic solvent based S Water based W Emulsion E All three are inside the scope of the same standard. A water-based impregnating varnish is… Read More: Solvent-Based vs Water-Based Insulating Varnish »
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 »
The thing that makes varnish testing different from most insulation testing is that you are testing two different materials. Before it cures, the varnish is a liquid. You care about how it flows, how it stores, how much solid it leaves behind, and whether it will catch fire in your shop. After it cures, it is a thin… Read More: How Insulating Varnish Is Tested: The IEC 60464-2 Methods »
“Best” is the wrong question — and here is the right one Ask a supplier for the best insulating varnish and you will get a product that is genuinely excellent at something. Whether it is excellent at your job is a separate matter. A varnish that performs beautifully in a vacuum pressure impregnation tank can be useless in… Read More: Best Electrical Insulating Varnish: How to Choose and Specify One »
Insulation is the electrical separation provided between conductive parts, together with the material or arrangement that provides it. You do not usually count it. A cable has insulation. A winding has insulation. You would not say a cable has “three insulations”. An insulator is either a discrete component designed to provide electrical insulation and, often, mechanical support —… Read More: Insulation vs Insulator: What Is the Difference? »
If a material blocks electricity, it probably blocks heat too. It sounds reasonable. It is wrong often enough to matter. Diamond is a wide-band-gap electrical insulator, and it conducts heat better than copper. Graphite felt conducts electricity and is used as high-temperature thermal insulation. Neither is an exotic edge case — together they are a clean demonstration that… Read More: Electrical Insulation vs Thermal Insulation »
An insulator has almost no charge carriers free to move. Apply a voltage and the charges inside it shift slightly but stay bound, so current flow is tiny compared with a conductor. That holds until the electric field gets strong enough, or the material weak enough, to tear carriers loose. Then you get breakdown. That is the mechanism.… Read More: How Does Electrical Insulation Work? »
Almost every wire inside a building, a panel, or a machine is insulated. Almost every phase conductor on a conventional overhead transmission line is bare. Both are correct engineering. Insulation is one way to keep current where it belongs. Clearance and physical separation are another. Which one gets used depends on voltage, environment, and how close anything else… Read More: Are Electrical Wires Insulated? »
Take a 400 V motor feeder and strip the cable back to bare copper. Nothing dramatic happens while the conductors stay apart. The air between them is doing the insulating, and dry air under normal atmospheric conditions holds off roughly 3 kV per millimetre. Treat that as a rule of thumb, not a fixed value — it shifts… Read More: What Is the Purpose of Electrical Insulation? »
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 »