Home › Blog › Electromechanical & Switchgear › Busbar, Transformer & Motor Insulation › How to spec insulation parts
How to Spec Busbar, Transformer, and Motor Insulation: What to Send H-O for a Quote
Insulation parts for switchgear and rotating equipment attract underspecified RFQs because the geometry looks like the whole story: a plate with holes, a folded liner, a wrapped strip. What the quote actually prices is the duty behind the geometry: the voltage and spacing the part must hold, the contamination it will see, the thermal class of the system it joins, and whether it carries load.
This is the ten-item checklist the H-O applications team works from for busbar supports, phase barriers, slot liners, layer insulation, and wraps, drawn from the parent application page's own engineering-review list, plus what engineering does with each item and what comes back.
Request a quote for your project →
The ten things to send, and what each decides
| Send this | What it decides |
|---|---|
| 1. The job: support, barrier, liner, or wrap | The mechanical form fork: structural laminate, formable paper, or thin film, decided before any brand talk. |
| 2. Working voltage, and any required creepage / clearance verbatim | The spacing context under IEC 60664-1. If your design already carries required distances, send them word for word; barrier geometry is designed to deliver them. |
| 3. Pollution degree / environment | Dusty, damp, or outdoor-adjacent compartments push the surface toward tracking-resistant composite or inorganic mica; clean sheltered gear keeps the economical laminate. |
| 4. Tracking class needed (CTI / material group) | Whether the grade's IEC 60112 CTI line must support a Group assumption in your spacing design; groups differ between grades of one family. |
| 5. Thermal class of the insulation system | The IEC 60085 class and UL 1446 system context. Substitutions stay inside the qualified system; rewind work matches the original machine's class, not just its thickness. |
| 6. Arc exposure: continuous or fault-event-only | Whether the duty pulls toward arc-rated muscovite or phlogopite mica, and whether the exposure is continuous radiant heat or a fault event; the answer changes the family. |
| 7. Mechanical load | Whether the part bolts to the frame, spans unsupported width, or takes fault forces, which is laminate territory, versus lining and wrapping duty for papers and films. |
| 8. Geometry: DXF, STEP, or PDF, slot map, or a sample part | The die, CNC, or waterjet program, with crease orientation for liners, fold allowances for wraps, and edge-quality and burr limits for laminates called out on the print. |
| 9. Flammability class requirement | UL 94 classes are per grade: FR4 carries the V-0 listing where plain G10 is unclassed, and the TDS stays with the order file. |
| 10. Prototype and production volumes | Converting method and price structure. Every part is made to order; recurring rewind quantities are held on the die or program for repeat orders. |
What engineering does with the list
Items 1 and 7 sort the mechanical form: glass-epoxy laminate for supports and load-bearing barriers, aramid paper for liners and formed parts, polyimide film or PEEK film for the thinnest layers.
Items 2 through 4 frame the surface story: where the pollution degree or tracking class pushes past standard laminate, the direction moves to Durostone composite (IEC 60112 data on its TDS) or muscovite mica, with phlogopite where item 6 says the zone runs extreme. Item 5 keeps the system qualification intact: the reply flags any substitution that would leave the qualified UL 1446 system rather than silently swapping.
Items 8 and 9 become the converting plan: waterjet-cut laminate with clean, delamination-free edges, creased liners cut to the slot map, mica laminated to backing, paper-film-paper laminations as one part. Item 10 sets method and pricing, and the reply cites each recommended grade's TDS values with the test method named.
What happens after you send it
- Drawing review. Engineering reviews the part against the vendor TDS: working voltage and spacing context, tracking class, thermal class, arc exposure, mechanical load, and the converted format that fits your line.
- Material direction and quote. A family and grade direction with the TDS attached, the conversion approach (waterjet, die-cut, creased, laminated), and pricing at your quantities.
- Samples. Typically 3 to 5 business days for common die-cut configurations on materials we keep on hand; liners sample with their creases so fit can be proven on the real slot.
- Production. Standard runs ship about two weeks after drawing approval, including waterjet-cut laminate and laminated configurations; expedited service is available. Ongoing parts run with material traceability and lot-code TDS records.
Documentation available on request: material technical data sheet, certificate of conformance, lot traceability, and first-article inspection, under our ISO 9001:2015 certified quality management system. H-O converts; we do not press laminate or make paper in-house, we state no creepage, clearance, or CTI number for your design, and assembly-level qualification (IEEE C37.20, IEC 61439) belongs to the equipment program.
The mistakes this checklist prevents
| Spec mistake | What it causes | Checklist item that catches it |
|---|---|---|
| Geometry-only RFQ | A quote for a plate, not an insulation part; the surface story goes unreviewed | Items 1 and 2 |
| Pollution degree assumed clean | A standard laminate barrier tracks after two dusty summers | Items 3 and 4 |
| Creepage read as a straight line | The gear passes its dry dielectric test and fails wet | Item 2, with the path traced in CAD |
| Material swap that leaves the qualified system | A better-looking data sheet quietly invalidates the UL 1446 system | Item 5, plus the substitution flag in the reply |
| Liner picked on dielectric numbers alone | The liner cracks at the forming radius against lamination edges | Items 1 and 8, crease orientation on the print |
| Laminate edges left to the cutting process | Fiber pull-out and micro-cracks become moisture paths at fastener holes | Item 8, edge quality and burr limits as conversion specs |
Frequently asked questions
Do you support motor rewind shops with small recurring orders?
Yes. Rewind work is recurring conversion: the same slot liners, wedges, separators, and layer insulation, cut to each machine's slot map and shipped to the bench. Send the slot dimensions or a worn sample part; engineering matches the original system's thermal class (not just its thickness), sets up the die or CNC program, and holds it for repeat orders. Made to order with MOQ varying by material and part.
Can you cross-reference the insulation grade on my print?
In most cases, yes. If your drawing calls out a laminate, mica, paper, or film by a brand part number, engineering identifies a comparable family from the lines we convert, matching on NEMA LI 1 grade, CTI group per IEC 60112, thermal class per IEC 60085, dielectric basis, and mechanical form. It is an industry cross-reference, not a guaranteed drop-in, and for insulation systems we flag when a substitution would leave the qualified UL 1446 system rather than silently swapping.
What does a slot-liner drawing need that a flat-part drawing does not?
The slot map and the creases. A liner is a formed part: crease orientation, fold allowances, and burr-free edges decide whether it survives insertion against lamination edges, so they belong on the controlled drawing rather than the shop floor. Where slot fill is the binding constraint, say so; the reply may propose a paper-film-paper lamination converted as a single creased part.
What lead time should I expect for samples and production?
Every insulation part is made to order, including samples. Samples typically ship in 3 to 5 business days for common die-cut configurations on materials we keep on hand; standard production runs ship about two weeks after drawing approval, including waterjet-cut laminate and laminated configurations; expedited service is available. MOQ varies by material and part, and prototype quantities through full production runs are equally accepted.
Send the checklist, get an insulation-part quote
Attach the geometry and as many of the ten items as you have. Rewind shops: a worn sample part and the machines thermal class are a complete starting point.
Samples typically ship in 3 to 5 business days for common die-cut configurations on materials we keep on hand; standard production runs about two weeks after drawing approval; expedited service is available. MOQ varies by material and part.
Family-owned in Winsted, Connecticut since 1971 · ISO 9001:2015 certified · OEMs worldwide send us a drawing — and get back their part.
Related reading
IndustryElectromechanical & Switchgear hubRead →
Request a quote for your busbar, transformer & motor insulation part
Send H-O your drawing or describe the part—engineering reviews every RFQ and converts samples on your geometry.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
References
- IEC 60664-1 (insulation coordination: the source of required creepage and clearance for your design); IEC 60112 (comparative tracking index).
- IEC 60085 (thermal classes) and UL 1446 (insulation systems; substitutions stay inside the qualified system); UL 94 (flammability, per grade); NEMA LI 1 (laminate grades).
- IEEE C37.20 and IEC 61439 (assembly standards for the finished gear).
- Manufacturer technical data sheets: glass-epoxy laminates, Durostone composite, mica, aramid paper, polyimide and PEEK films, glass-fiber paper.
This checklist supports a quotation workflow; it does not constitute design guidance for any specific assembly, and required spacings come from IEC 60664-1 applied to your design. Grade-level values are confirmed on the manufacturer's current technical data sheet, and insulation-system qualification under UL 1446 belongs to the equipment program. All parts are custom manufactured to order; minimum production run quantities vary by material and part.
H-O is a converter, not a raw-material producer, and does not certify finished switchgear, transformers, or machines.