Rockwell Automation 1336 3-20HP FRN 1.01-3.01 - Manual (Page 27)

Overview
Chapter 3
3-10
The 1336 is an AC adjustable frequency drive designed for use with a
standard, three-phase induction motor. The standard control is designed as
a constant torque, adjustable speed control with 150% overload capability
and is adaptable through programming to handle a wide variety of
applications.
The 1336 provides an exceptional output voltage and current waveform.
Special considerations however, must be taken when applying an inverter
to an existing motor. At slower speeds, cooling is not as effective due to
reduced fan rotation. Extended operation at full load torque at slow speeds
may damage the motor due to overheating.
100%
of
Motor
Frequency (Hz)
30 3
Torque
50%
of
Motor
Torque
60
Shown above is a typical curve plotting torque versus speed. At slow
speeds, if torque requirements continuously exceed levels shown above (10
minutes or longer), a motor rated for the required speed and torque range
must be used. To guard against mechanical problems, it is recommended
that the entire drive train machinery be checked for various limitations due
to the range of the Bulletin 1336.
!
ATTENTION: Motors may overheat when operated at rated
torque for long periods of time below 50% base speed due to the
decreased air flow of armature driven fans.
Motors may require special balancing if operated at more than
125% of base speed. Refer to the motor manufacturer for proper
sizing of the motor for the intended application.