Aspects regarding optimal design of high power squirrel cage asynchronous motors

The lately important development of some high precision electrical drives with great response speed, as well as the fact that the electrical machines exploitation is closer and closer to limit of stability have led to intense preoccupations, in the whole world and in our country, for the precise determination of the asynchronous motors parameters and the operation characteristics. This paper has got a novelty character, emphasizes the role of the electromagnetic stresses and the constructive dimensions in the total cost optimization for high power asynchronous motors; it is based on the utilization of the modern numerical methods and the afferent software. There have been performed significant simulations, which bring quantitative and qualitative information necessary for finding the final optimum solution, by considering the customer's restrictive conditions regarding the machine gauge. The optimization study has been done by the minimum total cost criterion, by considering twelve variables: A - the current sheet; B - the air gap magnetic induction; J
₁
, J
_2b
, J
_2i
- the current densities into the stator winding, rotor winding and the short-circuit ring; B
_j1
, B
_j2
- the magnetic inductions in the stator and rotor yoke; D - the machine diameter; δ - the air gap; β
_c1
, β
_c2
, β
_i
- the form factors for the stator slot, the rotor slot and the short-circuit ring. The optimization advantages are emphasized by the simultaneous presentation of the three variants of motors: V
_m
- the existing variant of motor; V
_o
- the optimum variant; V
_d
- the unfavourable variant (which has the maximum total cost). The total cost of the optimized motor decreased with 12,2% in comparison to the existing motor (designed by using the known method) and with 27,5% in comparison to the unfavourable variant. Since there are many such motors in use it appears that the saving is significant.