The international electrotechnical commission iec is the leading global organization that prepares and publishes. The different classes are defined by nema, ieee, underwriters laboratories ul and iec standards. The megger insulation tester is essentially a highrange resistance meter. Class 3 circuits are less common than class 2 circuits. Most terms used in iec publications are summarized in iec 60050 series, international electrotechnical vocabulary. Insulation classes for electric equipment in 1977, the electric instrument rules committee of the japanese industrial standards committee discussed the classes of electrical insulation and drew up jis c 4003. Insulation iec 60085 thermal class 3 iec 60085 thermal class 3 nema class 4 nemaul letter class um ot erature ed thermal endurance c3 materials 90 y 90c 105 er, 5 105 a 105 a 105c 120 er, 6 120 e 120c and erature b b c 155 estos lifetime erature 155 f 155 f 155c 180 erature erature 180 h 180 h 180c 200.
Ul performance materials electrical insulation systems and. Iec glossary international electrotechnical commission. By injecting a known dc voltage lower than the voltage for dielectric testing and then measuring the current flowing, it is very simple to determine the value of the resistance. Iec 60085 electrical insulation thermal evaluation and designation divides insulation into classes. The intent of the iec standard is to specify test methods that assure a given stator insulation design can prevent formation of pd in new windings and continue to suppress pd throughout the life of the motor type i insulation. The temperature rise of the induction machine is the permissible increase in temperature, above this maximum ambient, to allow for the losses in the motor. Under such circumstances, iec1 issued a recommendation on the temperature classes of electric insulators, followed by iec publication.
By definition, a horsepower equals the power to lift 33,000 lbs, 1 ft in 1 minute. Power and control cables normally have conductors of class 1 solid conductors or class 2 stranded conductors. The different classes are defined by nema, underwriters laboratories. Phasetophase insulation is stressed with the phasetophase voltage uphph um iec 600711, clause 7. For insulation coordination, iev 6040308 the following applies. Thermal electrotechnical commission standard electrical insulation thermal. Current transformers the oil filled lb hairpin design consists of 1 to 6 ushaped primary turns insulated with capacitance graded oilpaper insulation and housed in a porcelain housing. Understanding motor nameplate information nema vs iec. Power and control cables have plain annealed copper conductors.
Iec 623681 innovations introduces models introduces the concept of model for injury model for safety safeguards basic safeguard classifies energy sources class 1. Insulation class and temperature rise ver pangonilo, pee. When looking at motors, it is important to understand how the insulation functions and its practical application. This has a form that inorganic material is hardened with adhesives. Classes of insulation department of electrical engineering, iit. Gives guidance on the application of international standards in assigning a thermal class to electrical insulating materials eim or simple combinations of such materials iec 602161, to electrical insulation systems iec 62114 and to insulation for electrical. The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. Compared with the old iec standard from 2008, which defined three efficiency values for threephase asynchronous motors, the updated standard iec 60034301 has the additional efficiency class ie4. Linetoearth insulation is stressed with the linetoearth voltage ule umv3.
The different classes are defined by nema, underwriters laboratories ul, and iec standards. Classy materials with impregnated varnish or insulation oil iii classe insulation. The electrical insulation system is sometimes referred to as insulation class or thermal classification. Class b insulation consists of materials or combinations of materials such as mica, glass fibre, asbestos, etc. Insulation class often abbreviated insul class on nameplates, it is an industry standard classification of the thermal tolerance of the motor winding. Classes of electrical insulation, to clarify the classes of motor insulation and their maximum allowable temperatures table 1 table 1. Note 1 the enclosure of insulationencased class ii equipment may form part of the whole of the supplementary insulation or of the reinforced insulation. Selection of insulating mats for specific applications depends on the worker exposure to. Reference guide low voltage motors basics of iec motors.
Rules for classification and construction i ship technology. Iec 60228 specifies four different classes of conductors. Headquartered in geneva, switzerland, iec standards reach over 150 countries. Foreword 1 the international electrotechnical commission iec is a worldwide organization for standardization comprising all national electrotechnical committees iec national committees. The new standard iec 60034301 was published in march 2014, replacing its predecessor iec 6003430 from 2008. Iec 600341831 functional evaluation of insulation systems test procedures for formwound windings thermal evaluation and classification of insulation systems used in rotating machines in this, the test samples are exposed to thermal. The iec 60664 series of standards, insulation coordination for equipment within lowvoltage systems, defines the concepts of insulation coordination. Iec 600341 insulation class and temperature rise avsld. In principle, the value of the insulation resistance is very high but not infinite, so by. For good insulation, the resistance usually reads in the megohm range. Table 1 typical basic insulation levels basic insulation level, kv standard 1. Iec standards to test these types of electrical components.
Insulation classes the thermal insulation system is classified by a single letter iec60085. The international electrotechnical commission iec is a worldwide organization for standardization comprising. Depending on the thermal class, the winding overtemperature, which is the di. Insulation classes iec identifies many thermal classes maximum allowable total temperature c iec thermal class designation letter designation 90 y 105 a 120 e b 155 f 180 h 200 n 220 r 250. Iec, the international electrotechnical commission, is a nonprofit organization that develops and publishes standards concerning electrical technologies, of which a truly wide variety exists in todays modern world. This insulation class is one of the many key components of. Din en 600852008 electrical insulation thermal evaluation and designation superseded. Insulation may be grouped into the following recognised classes. The complete guide to electrical insulation testing. Note 2 if the equipment with double insulation or reinforced insulation throughout has an earthing terminal or earthing contact, it is considered to be of class i construction. Basics of iec reference guide 3 abb basics of iec motors a dictionary will tell you a watt is a unit of electrical power measurement based on amperes and volts an input unit, while a hp is a power measurement based on mechanical work an output unit. Iec 600341 classifies the temperature rise limits of insulation materials and specifies the maximum permissible temperatures that the various classes of insulation materials could withstand. This is determined by the ambient temperature, the heat generated at fully loaded conditions temperature rise, and the thermal capacity of the motor insulation.
Note a thermal class is not assigned to an eim as related to its use in an eis. Temperature tolerance class b is the most common insulation class used on most 60hz. Iec standards the motor standards can be grouped into two major categories. Each 10oc rise above the rating may reduce the motor lifetime by one half. Insulation on a motor prevents interconnection of windings and the winding to earth.
Insulation class a, previously in use, has been discontinued in view of its low working temperature. In north america, the national electric manufacturers association nema sets motor standards, including what should go on the nameplate nema standard mg 110. Insulation resistance measurement is based on ohms law. Temperature classes of electrical insulators threebond europe. Other materials or combination of materials, not necessarily inorganic, may be included in this class, if by experience or tests they can be shown to be. Insulation iec 60085 thermal class3 iec 60085 thermal class3 nema class4 nemaul letter class um ot erature ed thermal endurance c3 materials 90 y 90c 105 er, 5 105 a 105 a 105c 120 er, 6 120 e 120c and erature b b c 155 estos lifetime erature 155 f 155 f 155c 180 erature erature 180 h 180 h 180c 200.