Standard IEC Ratings

From Open Electrical

Contents 1 Introduction 2 Transformers 3 Motors and Generators 4 Cables

Introduction

Most IEC rated equipment have standard sizes that correspond to full sets or subsets of Renard numbers, especially from the four preferred series of Renard numbers outlined in ISO-3: R5, R10, R20 and R40.

Transformers

For transformer ratings under 10MVA, IEC 60076-1 suggest preferred values based on the R10 series: 10, 12.5, 16, 20, 25, 31.5, 40, 50, 63, 80, 100, and multiples of 10ⁿ. For example, the preferred transformer sizes from 500kVA to 4000kVA are: 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150, 4000.

Motors and Generators

IEC 60072-1 Table 7 suggests the following preferred ratings (based on a subset of the R40 series) for motors (in KW) and generators (in kVA):

0.06	0.09	0.12	0.18	0.25	0.37	0.55	0.75	1.1	1.5	1.8*	2.2	3*	3.7	4*	5.5	6.3*	7.5	10*	11	13*	15	17*	18.5
20*	22	25*	30	32*	37	40*	45	50*	55	63*	75	80*	90	100*	110	125*	132	150	160	185	200	220	250
280	300	315	335	355	375	400	425	450	475	500	530	560	600	630	670	710	750	800	850	900	950	1000

(*) Note that these are "secondary series" ratings and are only to be used in cases of special need.

Cables

Standard cable sizes (in mm²) are as follows:

0.5

0.75

1

1.5

2.5

4

6

10

16

25

35

50

70

95

120

150

185

240

300

400

500

630

800

1000