Motor & Transformer Lead Sleeving
The lead is the hottest flexible part of a machine. Class H silicone coated fiberglass sleeving for motors is chosen on the measured hot spot, not on the class label, and on how the sleeve is assembled onto a lead that may already be terminated.
The problem this page solves
Lead insulation fails before the winding does, because the lead is thin, it bends, and it passes close to the hottest part of the machine on its way out. The temperature at that point is not the machine's ambient rating and not the average of the enclosure: it has to be measured.
Two families cover the duty: silicone-coated fiberglass, which is a slip-on sleeving used over an assembled lead, and silicone rubber heat-shrink, which recovers onto the lead before the terminal is fitted. They share a published range of -60 to +200 °C and differ in assembly, not in rating.
The coating question is the one that causes trouble later. Raw braid sheds where the cut end rubs. A construction with the woven face inward and a silicone bore against the conductor behaves differently from one with silicone on the outside. Which face has to be smooth depends on what the sleeve touches.
- Measured hot spot : read the temperature at the lead's closest approach to the winding or core, not the class label of the machine.
- Shedding : a coated construction or a fiber-bore construction controls where the abrasion happens.
- Impregnation : varnish and oil change the coating, so the grade matters more than the family.
- Assembly order : heat-shrink cannot pass over a crimped lug, which decides which construction is usable.
Technical specification and published ratings
Every figure below is the published value on the Wellele product page for that item. Where a value is still being confirmed, the page says so and this table says so.
| Wellele Series-Type | Construction | Published temperature | Form | Published reference | Cross-identification |
|---|---|---|---|---|---|
| WLL-FG-SIL | Fiberglass braid with external silicone coating | -60 to +200 °C | Slip-on, non-shrink | UL 1441 scope being confirmed with batch documentation - not claimed here | Bentley-Harris Ben-Har 1151 XL · Suflex Silicone Sleeving 7000 |
| WLL-FG-IF | Fiberglass bore against the harness, silicone outer skin | -60 to +200 °C | Slip-on, non-shrink | None claimed | No published cross-reference |
| WLL-FG-IR | Silicone bore against the lead, fiberglass outer skin | -60 to +200 °C (rubber core governs) | Slip-on, non-shrink | None claimed | No published cross-reference |
| WLL-SIL-2X / WLL-SIL-7X | Silicone rubber, heat-shrink wall | -60 to +200 °C | Heat-shrink, 2:1 / 7:1 | None claimed | No published cross-reference |
| WLL-FG-DL | Double-layer fiberglass braid, high density | -60 to +550 °C catalogued; continuous and short-term split pending | Slip-on, non-shrink | None claimed | No published cross-reference |
| WLL-FG-EXT | Rigid smooth-tube fiberglass | Not published | Push-on | None claimed | No published cross-reference |
| WLL-SIL-TAPE (HTF73) | Silicone self-amalgamating tape | -60 to +280 °C | Wrap, fuses at room temperature | None claimed | No published cross-reference |
| WLL-PI | Polyimide with fiberglass reinforcement | Pending verification | Slip-on, non-shrink | Pending verification | No published cross-reference |
Insulation class and material rating are not the same thing. Class H (180 °C) and Class N (200 °C) describe the insulation system of the machine; each sleeve carries its own material temperature rating, and the two are matched in your design rather than certified as a system by us. On UL 1441: the recognition scope for the silicone-coated fiberglass sleeving is being confirmed with batch documentation, and until that file is complete we do not publish a UL 1441 claim for it. What we can state today is the material, the construction and the published temperature range.
Selected products for this application
What to send for a construction recommendation
Measured temperature
Environment
Assembly order
Lead geometry
Which face must be smooth
Documentation
Engineering questions we are asked
Which construction should I choose for a Class H or Class N lead?
Start from the worst temperature at the lead's closest approach to the winding or core rather than from the machine's class label, and check whether the run sits in air, in varnish or in oil. Class H and Class N describe the insulation system of the machine. The sleeve carries its own material rating and is matched to it in the design. Slip-on and heat-shrink constructions reach the same published range and differ in assembly.
Does the fiberglass braid shed and contaminate the winding?
Raw braid can shed where the cut end rubs against a winding or a slot liner. A coated construction with silicone on the outside, or a construction with a silicone bore and fiberglass outside, changes where the abrasion happens. Tell us which face has to be smooth and we match the construction instead of selling you the cheapest braid.
Does UL 1441 cover the silicone-coated fiberglass sleeving?
Not as a published claim. The recognition scope for this sleeving is being confirmed with batch documentation, and until that file is complete we do not put a UL 1441 claim on the product. What we can state now is the material, the construction and the published temperature range. If your project requires UL recognition in writing, ask before you buy and we will tell you the status at that date.
Should a transformer lead use slip-on or heat-shrink?
Assembly decides it. Heat-shrink recovers onto a lead that is already terminated, but it cannot pass over a lug, so it has to go on before the terminal is crimped. Slip-on sleeving goes over a completed assembly and can be clipped, but it does not grip, so it can move if it is not secured at both ends. Tell us the assembly order and whether the joint is already made.
What happens to the sleeve in varnish or oil?
The construction has to suit the impregnation process, not only the running temperature. Varnish can stiffen a coated braid, and oil can swell or extract some coatings, so the grade matters more than the family. Tell us the impregnating varnish or the oil specification and we will confirm which of our grades is used in that process.
Send the lead position and the process
Machine insulation class, measured hot-spot temperature, air or varnish or oil, the assembly order and the lead diameter. We return the construction and the grade with its published rating.
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