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Type
Keywords

 

Insulating-Enameling

Enameling
A film insulating process is used to apply a wide variety of enamels to wire ranging in size from 0.025” to 0.0005” in diameter.  The wire is passed successively through a liquid bath of enamel and an oven that bakes and cures the enamel on the wire until the required “buildup” or thickness of enamel is achieved.  Approximately, 25 enamel machines are in operation at all times.

Enamel Insulation Specifications

Type

Code

Temp

NEMA

Formvar

FV

105 o C

MW-15

Nylon

NY

105 o C

MW-6

Formvar / Nylon

FV NY

105 o C

MW-17

Formvar / Butyral

FV BU

105 o C

MW-19

Polyurethane / Nylon / Butyral

PN BU

155 o C

MW-28

Polyurethane

PU

155 o C

MW-79

Polyurethane / Nylon

PU NY

155 o C

MW-80

Polyester

IS

180 o C

MW-5

Solderable Poyester     TR

180 o C

   MW-77

Polyesterimide

IM

180 o C

MW-30

Polyesteramide imide overcoat

AP

200 o C

MW-35

Polyimide

ML

240 o C

MW-16

Polyimide

RK

240 o C

MW-161

Polyimide

DG2

220 o C

MW-16

Polyimide VG Bond Coat

ML VG

240 o C

No NEMA

1-Tested at 300° C for 1,000 hours

2 - P.D. George Co.

PTFE Coating

Ceramic Insulation

Ceramics
California Fine Wire Company has produced high temperature flexible ceramic insulated fine wire for many years. The semi-cured wire requires a slow heat treatment after the wire is wound or affixed. The wire is not flexible after this final cure and is then suitable for high temperature use.

Conductors
One point, often overlooked, in the design of a high temperature insulated wire is that the conductor is as important, or possibly more important than the insulation itself. CFW ceramic coatings meet the requirements for insulation. They can be applied to almost any conductor.

Basically, there are two classes of conductors. One is a low resistance conductor for use as a magnet wire. The other is a broad class of special conductors each designed to fit a specific requirement. Examples of this second type are pure metals such as Nickel or Platinum for use as resistance thermometer wires. These, because of their resistance to oxidation and grain growth, offer no problems. High resistance wires offer no problems since they are mainly alloys of Nickel and Chromium (Stablohm 675 and 800), all of which have excellent oxidation resistance. Constantan (Nico), another special purpose alloy, having a high resistance and a low temperature coefficient of resistance, works well over all temperature ranges. Silver (99.99%) and Silver alloys (Alloy 406, 411) work well in special sensor applications also.

Alcal Type "E" ceramic insulation can be applied to following materials:

Platinum, Gold, Silver, Palladium, Rhenium, and most precious metal alloys, Stainless Steels, and Nickel-Chromium Alloys, Nickel Clad Copper, Nickel Clad Sliver, Aluminum and Aluminum Alloys, Aluminum Clad Copper, Constantan, Chromel P, and Alumel.

Handling Procedures
Ceramic coating is primarily a refractory-glass compound and can withstand flexibility and braiding requirements consistent with normal coil winding practices. It should not be abused by scraping, excessive handling, severe pressure from test leads, or any similar harsh treatment.

Ceramic coating serves as a standoff insulation and is not moisture resistant. It is, therefore obvious that these coatings cannot be tested or operated in Mercury, salt water, or any solution capable of making electric contact through minute crevices in the coating. Since adequate coating thickness is less than one half of a mil (.0005), the presence of moisture during voltage application can produce breakdown conditions, which are entirely independent of the insulating properties of the coating. If this condition occurs and the applied voltage does not exceed the voltage of the Ceramic Insulation rating, a continuing application of the low voltage may be applied to remove moisture form the insulation, prior to performing any electrical testing. For normal "curing" instructions, see "Curing Instructions" in the next section.

Protective Insulations
Alcal Type "E" can be overcoated with various types of enamels, such as, Polyurethane, Pyre-ML, Polyester, and Silicon. The application of these insulations will not normally change the temperature rating of the ceramic coating. The reason is that the final cure temperature (See "Curing Instructions") will cause the wire enamels to volatilize. The purpose of the overcoat is to protect the ceramic insulation in a harsh winding environment. This protective insulation is not required and may not be feasible in some applications

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