
AC and DC Motors 115
5.1.3 torqUe–sPeed CharaCteristiC MatChing
Matching the torque versus speed characteristic of the induction motor with that
of the load is an important consideration for system design. The motor connected
to a high-torque load during start must have high starting torque, or else it will not
start. Some motors have high starting torque but lower efciency compared to others.
The high starting torque requires rotor with high resistance, resulting in poor ef-
ciency under running conditions. The National Electrical Manufacturers Association
(NEMA) classies motor designs according to the starting torque and the maximum
brea ...