Motordesign
Motors can be designed for different features of starting torque, starting current and slip.
Standard motors designed to IEC standards are designated NY, N, H and HY; while motors designed to NEMA carry letters A, B, C and D. Note that the specifications are not totally compatible, but are combined in Table
For voltage source PWM inverter operation, design NY or A is the best suited, while design Nor 8 will normally give satisfactory service. For other motors consult the manufacturer.
Specially designed inverter fed motors are offered for a number of specific low power requirements, such as high speed operation, where the base speed may be increased from 3000 r/min to 4000 or 5000 r/min. However, special designs of inverter fed motors are more widely used for higher powers and will generally carry a special name and rating plate designating the permitted duty range.