European design trends in standard class F, AC motors

In 1963, an agreement in Europe (EEC and EFTA) was reached to designate output ratings to frame sizes as they are specified in IEC publication 72-1 and 72-2. With the 1963 document, the important motor producing countries agreed finally on an electric motor which had passed through the various development phases and at that time represented a design which generally could be agreed on. Figure 1 exemplifies the various development steps of electric motor building since 1900 relating to size and output. This relationship (framesize-output rating) has also been adopted by the East European countries (Comecon). For about 7 to 8 years, therefore, a three phase AC standard motor with squirrel cage rotor and IEC dimensions has existed in Europe for the framesize range 56 up to 315 (2⅝" to 12½") in protection mode IP-23 1 and IP-44.2 Further extension to the framesizes 355 and 400 is expected to take place during this year upon appearance of IEC publication 72-A. These European IEC standard motors have been fully accepted and adopted in the various areas of the industry. By means of this framesize-ouput rating relationship full exchangeability is obtained regardless of brand. Significant savings in stock keeping for all branches in the industry have been achieved. Due to national peculiarities of the different countries, insignificant deviations from this framesize-output rating relationship are detectable, notably for framesize 90 motors. This, however, does not lessen the advantages of this international standardization.