Wire insulation is a very important factor in motors. Wire insulation prevents wire shorts in two ways:

1. abrasion resistance - better abrasion resistance reduces the likelihood of short circuits when winding wire. If you have debris in your motor's stator insulation, or if you tend to rub the wires while winding, it can be the difference between success and failure.2

. Heat Resistance - The more heat the wire can withstand, the hotter the motor will run without burning up. I have seen a motor burn out (i.e., burn into an open circuit) parallel wires, but continue to run under high temperature insulation. Note that high temperature wire can be difficult to solder. It is often considered “unsolderable” which means you have to burn/scrape/sand off the insulation before you can solder it.

Double Coated Wire
In some cases, wire may have a double layer of insulation. The outer coating is usually a smooth, highly abrasion-resistant coating, such as polyamide (aka nylon), which helps wind the wire. The inner coating is usually a heat-resistant coating. Sometimes the coatings are mixed to increase chemical resistance.

Common types of insulation
Enamel (Formvar): low temperature (105 degrees Celsius - Class A), poor abrasion resistance, average chemical resistance. Cheap, but works well for winding coils on plastic.

Mica: low temperature (130 degrees Celsius - class B), excellent abrasion resistance. Not very common these days.

Polyamide (aka Nylon): Good abrasion resistance at low temperatures (usually below 155 degrees Celsius - class F). Common in motor wires. Often used as a jacket because of its abrasion resistance and low coefficient of friction.

Polyester - High temperature (usually 155-200 - Class F), poor abrasion resistance. Sometimes not weldable and coatings should be removed chemically or by burning/cleaning. Usually used in combination with polyamides.

Polyurethane: Moderate temperatures (155-180 degrees Celsius - grades F and H). Often used with nylon as a wear-resistant coating. Abrasion resistance is average.

ML - Polyimide (not to be confused with polyamide) - Very high temperature (up to 240 C - class H), excellent chemical resistance, average abrasion resistance. Often used in combination with nylon to improve abrasion resistance (polyamideimide).

Polyamideimide - Very high temperature (200-240 C - Class F and H), high abrasion resistance. Used for non-solderable wires where the coating must be abraded off due to chemical resistance. Below are

some examples of wires
Radio Shack: Formvar enameled wire (105 degrees Celsius)
GoBrushless Newbie: DBHPN - Double Nylon (155 degrees Celsius)
Micro Dan: Polyester/Nylon (180 deg C)
Belden CDT - polyurethane/nylon (155 deg C)
Dearborn CDT - polyester/polyamideimide (200 degrees Celsius)

So the next time you need to buy wire, maybe this will help you a little bit in finding the best wire for your motor.