Which Insulation Class Is Better F Or H

The hot spot is a point at the center of the motor s windings where the temperature is higher.

Which insulation class is better f or h.

Hot spot temperature rise. So if we look at a class f insulated motor which will be happy running at 155 c and then subtract 30 c we get a surface temperature of 125 c. 1800 hours with class b insulation. Similarly a class h system operating at a class f temperature rise will provide the same life expectancy as a class f system operating at a class b temperature rise.

The electrical insulation system is sometimes referred to as insulation class or thermal classification the different classes are defined by nema underwriters laboratories ul and iec. There are basically four classes of insulation a b f and h class f being the most commonly used. Example a motor operating at 180 o c will have an estimated life of. Class a is an older form of insulation utilizing organic varnishes and resins available many years ago.

Average winding temperature rise. Nema insulation classes do away with guessing and give the motor manufacturer a defined framework to operate in. The surface temperature of the motor is typically 30 c lower than it is at the windings. Class c insulation consists of materials or combinations of materials such as mica porcelain glass quartz with or without an inorganic binder beware a few older applications used asbestos.

Other materials or combinations of materials may be included in this class if by experience or tests they can be shown to be capable of operation at temperatures above the class h limit. It is important to be aware that insulation classes are directly related to motor life. Moving from an insulation system class f with a hotspot of 140 c to a hotspot of 160 c the s9 ratings are able to be increased by 7 with an improvement in design of. The electrical insulation system for wires used in generators electric motors transformers and other wire wound electrical components is divided into different classes by temperature and temperature rise.

8500 hours with class f insulation. Class 150 or 130. As can be seen from the above table hot spot over temperature allowance for a b f and h are respectively 5 c 10 c 10 c and 15 c. Each insulation class has a margin allowed to compensate for the motor s hot spot.

These insulation classes were established to meet motor temperature requirements found in industrial applications.