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Product

High-temperature wires & cablesSRML · UL 3231 & 3070600 V / 1,000 V · 200 °C24 AWG to 4/0 AWG

Silicone Rubber Motor Lead Wire (SRML / UL 3231 & UL 3070)600 V / 1,000 V 150–200 °C fiberglass-braided silicone motor & transformer lead wire

Heavy-duty flexible motor and transformer lead wire (SRML, UL AWM Style 3070 150 °C & Style 3231 200 °C) from 24 AWG to 4/0 AWG, pairing rope-lay tinned copper conductors with vulcanized silicone rubber and a varnish-bake-resistant fiberglass braid.

Flame-retardant
Oil-resistant
Outdoor & humid
Approved
Order designation
SRML / UL 3231 · 10 AWG
Nominal OD
5.73 mm
SiR wall
1.14 mm
Mass ≈
69.0 kg/km
Max. DC res.
3.50 Ω/km
Check against my drumAll sizes (12)
Request a quoteDatasheetWhatsApp
Engineering reply in 2 business hoursCut-to-length export drumsEN 10204 3.1 certificate per drum
Temp. rating
150 / 200 °C
Class F (155°C), H (180°C) & N (200°C)
Rated voltage
600 V / 1,000 V
UL 3070 / 3231 & CSA AWM
Insulation
SiR + FG Braid
Silicone + VPI-ready glass braid
AWG range
24 AWG–4/0 AWG
0.20 to 107 mm² (up to 500 kcmil)
Conductor
Flexible SnCu
ASTM B33 / B174 flexible tinned Cu
Min. bend radius
6 × OD
Motor peckerhead & coil routing

Typical values for this cable type, based on UL 758 Styles 3070 & 3231 (SRML) — confirmed in the datasheet and quotation for your order.

Application fit

Is SRML / UL 3231 / UL 3070 right for your machine?

Heavy-wall silicone rubber motor lead wire (-60 °C to +180 °C) engineered for Class H stator windings, VFD traction motors, generators and dry-type transformers.

Motor stator, traction & converter leads

Suitable

Primary duty — direct connection to Class H motor stators, generator coils and transformer windings.

Switchgear & control cabinet wiring

Suitable

Flexible high-current power jumpers inside converter cabinets and motor terminal boxes.

Furnace, kiln & high-temp zone

Suitable

Withstands +180 °C continuous ambient heat in furnace fan motors and kiln drives.

Trailing & towing

Not suitable

Single-core motor lead — must be installed in conduit, tray or housing, never dragged on the ground.

Use DLO Locomotive Cable

Motorised monospiral reel

Not suitable

Not intended for reeling drums or tensile suspension.

Use (N)SHTÖU Reeling
Typical machinesClass F, H & N electric motors & generatorsDry-type distribution & drive transformersTraction, mill & crane motor rewindsVFD line/load reactors & inductorsIndustrial furnaces & heat-treating fansHigh-current power electronics cabinets

Construction

Layer by layer

A flexible concentric or rope-lay stranded tinned copper conductor (24 AWG to 4/0 AWG) is insulated with heavy-wall vulcanized silicone rubber (0.76 to 2.41 mm) and armored with a closely woven, varnish-bake-compatible fiberglass braid.

123
Schematic, not to scale — generated from the layer data
#LayerMaterial & reference
1Flexible tinned copper conductorBunched or rope-lay stranded tinned annealed copper per ASTM B33 / B174, 24 AWG to 4/0 AWG (up to 500 kcmil)ASTM B33 / UL 758
2Heavy-wall vulcanized silicone rubberExtruded cross-linked silicone rubber (0.76 to 2.41 mm nominal radial wall by AWG size) rated 150 °C (UL 3070) or 200 °C (UL 3231)UL 758 Styles 3070 & 3231
3Varnish-compatible fiberglass braidClosely woven E-glass braid (0.20 to 0.50 mm) treated with high-temperature moisture- and varnish-resistant saturantUL 758 Style 3231

SRML / UL AWM Style 3070 · 150 °C · 600 V

Classic 150 °C Silicone Rubber Motor Lead wire for Class B (130 °C) and Class F (155 °C) motor and transformer leads

UL AWM Style 3231 · 200 °C · 600 V / 1,000 V (24 AWG to 4/0 AWG)

Full 200 °C braided silicone motor lead wire for Class H (180 °C) and Class N (200 °C) VPI-baked windings

Technical data

Ratings & operating limits

Typical values: Typical values for this cable type, based on UL 758 Styles 3070 & 3231 (SRML). Values for your order are confirmed in the datasheet and quotation.

Electrical

Rated voltage
600 Vac standard (SRML / UL 3070 / UL 3231) and 1,000 Vac heavy-duty option
Dielectric & spark test
2.0 kV Vac dielectric withstand (3.0 kV on 1,000 V) + 6.0 kV Vac in-line spark test per UL 758
Conductor stranding & tinning
Flexible stranded tinned annealed copper per ASTM B33 / B174 (concentric or rope-lay from 24 AWG to 4/0 AWG / 500 kcmil)

Thermal

Operating temperature & thermal class
−60 °C to +150 °C (SRML / UL 3070) or −60 °C to +200 °C (UL 3231) for NEMA Class F (155 °C), Class H (180 °C) & Class N (200 °C) windings
Stator bake & thermal shock
Withstands repeated 200 °C VPI varnish cure cycles without insulation cracking or stiffening

Mechanical

Silicone & braid wall schedule
0.76 mm (24–14 AWG), 1.14 mm (12–10 AWG), 1.52 mm (8–2 AWG), 2.03 mm (1–3/0 AWG), 2.41 mm (4/0 AWG) silicone wall + treated fiberglass braid
Minimum bending radius
6 × overall diameter (stator coil end-turns and motor terminal boxes)

Resistance

Varnish, flame & corona resistance
UL VW-1 / Horizontal flame & CSA FT1; compatible with VPI polyester, epoxy and silicone insulating varnishes and 200 °C bake cycles
Ozone & inverter-duty resilience
High corona and ozone resistance for inverter-fed (VFD) motor stator end-turns

Reference standards

Applicable standards
UL 758 AWM Styles 3070, 3231 & 3122; CSA C22.2 No. 210 (AWM I A/B) & No. 49 (SEW-2 / SEWF-2); ASTM B33
Environmental compliance
RoHS & REACH compliant

Identification

Available UL & CSA designations
SRML / UL 3070 (150 °C, 600 V) & UL 3231 (200 °C, 600 V / 1,000 V, 24 AWG–4/0 AWG)
Standard braid colours
Black, White, Red, Blue, Yellow, Brown, Orange, Green & tracer combinations

Sizes

12 standard gauges across SRML / UL AWM Style 3231 & Style 3070 (18 AWG to 4/0 AWG)

Nominal flexible tinned copper stranding, silicone wall, fiberglass braid thickness, overall diameter, mass and max DC resistance at 20 °C.

Dimensions, stranding & DC resistance
Style · AWG sizeSize
AWG		CSA ≈
mm²		Stranding
(count/AWG)		Cond. Ø
mm		SiR wall
mm		Braid
mm		Nominal OD
mm		Mass ≈
kg/km		Max. DC res. (20 °C)
Ω/km		Enquiry
SRML / UL 3231 · 18 AWG18 AWG0.8216/301.220.760.203.1415.022.40
SRML / UL 3231 · 16 AWG16 AWG1.3126/301.500.760.203.4220.014.00
SRML / UL 3231 · 14 AWG14 AWG2.0841/301.880.760.203.8028.08.90
SRML / UL 3231 · 12 AWG12 AWG3.3165/302.361.140.255.1448.05.60
SRML / UL 3231 · 10 AWG10 AWG5.26105/302.951.140.255.7369.03.50
SRML / UL 3231 · 8 AWG8 AWG8.37133/293.731.520.307.37115.02.20
SRML / UL 3231 · 6 AWG6 AWG13.3133/274.701.520.308.34168.01.40
SRML / UL 3231 · 4 AWG4 AWG21.2259/285.901.520.359.64252.00.89
SRML / UL 3231 · 2 AWG2 AWG33.6259/267.421.520.3811.22378.00.56
SRML / UL 3231 · 1/0 AWG1/0 AWG53.5259/249.352.030.4514.31595.00.35
SRML / UL 3231 · 2/0 AWG2/0 AWG67.4259/2310.502.030.4515.46735.00.28
SRML / UL 3231 · 4/0 AWG4/0 AWG107.2427/2313.252.410.5019.071,140.00.18
  • Typical values for this cable type; dimensions and weights for your order are confirmed in the quotation.
  • Smaller signal gauges (24–20 AWG) and larger power sizes (250 to 500 kcmil) are manufactured to order under UL 3231.

Reel check

Will it fit your machine?

A first screen using datasheet values. Engineering confirms drum geometry, acceleration and tension with your quotation.

Check results

Enter your drum core diameterMinimum for this size is about 68 mm
Minimum bending radius
34 mm
Min. drum core diameter
≈ 68 mm
Cable weight on drum
6.9 kg
Outer diameter
5.7 mm
Indicative only: based on the datasheet outer diameter and 6 × OD bending radius. Current derating for wound layers per DIN VDE 0298-4 is assessed separately.

Quality & approvals

Testing & inspection

Routine tests on every production length, sample and type tests per batch — documented on an EN 10204 3.1 inspection certificate.

  1. ConductorClass 5 stranding
  2. Spark test100 % in-line
  3. Lay-upCores, earth, fillers
  4. SheathingInner, braid / screen, outer
  5. Electrical testsAC voltage, resistance
  6. DimensionsOD, wall thickness
  7. Inspection documents & dispatchDrum & dispatch
Testing & inspectionTest value / referenceFrequency
Routine tests
AC dielectric & in-line spark test2.0 kV Vac (600 V) or 3.0 kV Vac (1,000 V) dielectric test + 100% 6.0 kV spark test per UL 758Every spool
Conductor DC resistance checkVerified at 20 °C per ASTM B33 / B174 flexible tinned copper limitsEvery spool
Sample tests
UL VW-1 / Horizontal flame & FT1 testFlame retardancy verified per UL 758 / UL 1581 and CSA FT1Production lot
200 °C heat aging & varnish compatibilityElongation and dielectric retention after 200 °C aging and −60 °C cold bendProduction lot

Inspection certificate

Issued with every drum, listing the routine test results for that length.

Product approvals

SRML · UL 3231 & 3070CE · LVDRoHS · REACH

Company certificates

ISO 9001ISO 14001ISO 45001VDE marks approvalUL / cULCE · LVD / EMC

Marking & supply

Ordering & delivery

Sheath marking

TEBAOFLEX · E-file UL AWM STYLE 3231 200°C (or 3070 150°C) 600V/1000V SRML · CSA AWM I A/B FT1
Delivery form
Reels, spools, barrel packs and pre-lugged motor lead harnesses
Lengths
Standard reel lengths and custom cut/terminated stator lead sets
Certificate
EN 10204 3.1 inspection certificate with every dispatch
Quote response
Engineering specification and quote within 2 business hours

Technical documents

Downloads

PDFSilicone Rubber Motor Lead Wire (SRML / UL 3231 & UL 3070) – technical datasheet12 sizes · construction, technical data, approvalsXLSXSRML / UL 3231 / UL 3070 spec data (Excel)All 12 sizes with dimensions and data, for your BOM or quotation
Revision
2026-10-20
Updated
2026-10-20

FAQ

Questions engineers ask first

Not covered here? Send your drawing — an engineer replies within 2 business hours.

What is the difference between SRML, UL 3070 and UL 3231?
'SRML' stands for Silicone Rubber Motor Lead, the classic North American designation for flexible tinned copper insulated with vulcanized silicone rubber under a treated fiberglass braid. Under UL 758, Style 3070 is the 150 °C / 600 V recognition and Style 3231 is the full 200 °C / 600 V (and 1,000 V) recognition spanning up to 4/0 AWG and 500 kcmil.
Can SRML / UL 3231 withstand vacuum-pressure impregnation (VPI) and stator baking varnish?
Yes. Both the vulcanized silicone rubber wall and the high-temperature saturant-treated fiberglass braid tolerate standard polyester, epoxy, alkyd and silicone insulating varnishes and 180–200 °C oven bake cycles without cracking or delamination.
Why does SRML use tinned copper rather than bare copper?
Above 120 °C, bare copper oxidizes rapidly and can catalyze thermal aging of elastomers. Tinning each strand per ASTM B33 prevents oxidation during varnish baking and keeps crimp lug contact resistance low.
Should SRML be used inside oil-filled transformers?
No. SRML is designed for air-cooled or VPI dry-type transformers and Class F/H/N rotating machines; silicone rubber swells when continuously immersed in mineral transformer oil.

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Silicone Rubber Motor Lead Wire

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