Torque
is the product of a force and the radius at which it is applied. The
British unit of torque is pound-feet and in smaller motors this unit is
reduced to ounce-inches. The metric unit of torque is Newton-meter.
Few
motors produce a single value of torque over their entire speed range
so that a torque vs. speed curve is often necessary for torque
evaluation. Definitions of terms used to describe specific points on the
curve are listed below along with definitions of some other commonly
used terms for motor torque specification.
Pull-In
Torque: the maximum torque at which a synchronous motor (stepping motor
included) can accelerate its load to synchronous speed.
Pull-Out
Torque: the maximum torque which a synchronous motor (stepping motor
included) can develop and still maintain synchronous speed.
Full-Load Torque: the torque developed by a non-synchronous motor at its rated full-load speed.
Breakdown
Torque: the maximum torque that the motor can develop; it occurs as a
point on the speed-torque curve below synchronous or full-load speed.
#FengTech Motor
Locked-Rotor Torque: the torque developed with the rotor at standstill.
Holding
or Static Torque (Stepping Motor): the torque required to displace the
rotor from its equilibrium position with one or more stator phases
energized with the rotor at rest.
Detent
or Residual Torque (Permanent Magnet Motor): the torque developed in an
unenergized motor when the permanent magnet rotor is displaced from a
position of minimum stator eluctance.