There are several types of AC (e.g. induction, synchron […]
There are several types of AC (e.g. induction, synchronous) and DC (e.g. series, shunt, permanent magnet) motors. Each of those types can be designed (within some constraints) to have different torque-speed relationships.
In North America, AC induction motors typically arewashing machine ac motor built to one of several NEMA standard designs. NEMA design B is most common (especially for pumps and fans) and has its torque peak just below synchronous speed; design D has its peak at zero speed (so it can handle high starting inertia and shock loads).
Series-connected DC motors also have maximum torque at zero speed, so they were most often used in railroad and elevator traction (though in both applications are now being supplanted by AC motors with electronicmotor for washing machine variable frequency drives. They are still used in electric hand drills and other tools. Shunt-connected DC motors have a relatively level torque up to nearly their rated speed, where it drops off.