Product Manual

AC Polyphase (Three-Phase)
Polyphase induction motors have a
high starting torque, power factor, high
efficiency, and low current. They do not
use a switch, capacitor, relays, etc., and
are suitable for larger commercial and
industrial applications.
Polyphase induction motors are speci-
fied by their electrical design type: A,
B, C, D or E, as defined by the National
Electrical Manufacturers Association
(NEMA). These designs are suited to particular classes of applications
based upon the load requirements typical of each class.
The table on the next page can be used to help guide which design type
to select based on application requirements.
Because of their widespread use throughout industry and because their
characteristics lend themselves to high efficiencies, many types of
general-purpose three-phase motors are required to meet mandated
efficiency levels under the U.S. Energy Policy Act. Included in the
mandates are NEMA Design B, T frame, foot-mounted motors from
1-200 HP.
-17-
A heavy-duty polyphase motor with cast-iron frame.