W21 Prime motors are supplied with class F insulation and
Class B (80 K) temperature rise at normal operating conditions
(unless otherwise specified). The difference between the tem
perature of the class F insulation (155 K) and the temperature
rise of the design (80 K) means that, in practice, W21 Prime
motors are suitable to supply output ratings 15% above the
rated values up to a limit where the temperature rise reaches
the temperature rise value of the insulation class.
All W21 Prime motors are wound with the WISE® insulation
system which consists of enameled wire meeting tempera
tures up to 200°C and impregnated with solvent-free resin.
The WISE® system also permits motor operation with variable
speed drives.