Which Insulation Class Is Better F Or H

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.

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. There are basically four classes of insulation a b f and h class f being the most commonly used. 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. The surface temperature of the motor is typically 30 c lower than it is at the windings.

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. Example a motor operating at 180 o c will have an estimated life of. These insulation classes were established to meet motor temperature requirements found in industrial applications. Only 300 hours with class a insulation.

8500 hours with class f insulation. Nema insulation classes do away with guessing and give the motor manufacturer a defined framework to operate in. Tens of thousands of hours with class h insulation. Class 150 or 130.

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. 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. Each insulation class has a margin allowed to compensate for the motor s hot spot.

It is important to be aware that insulation classes are directly related to motor life. 1800 hours with class b insulation. Class a is an older form of insulation utilizing organic varnishes and resins available many years ago. Average winding temperature rise.

Insulation class b f h maximum winding temperature 130 c 155 c 180 c 0 40 120 130 155 145 165 180 c 20 maximum ambient temperature minimum ambient temperature 30 minimum ambient temperature 10k 105k 40 c class f b 155 c 80k safety margin 25k 150 c ptcs setting 2 c0 2 c0 2 c0 regal beloit bv mors 2.