6
2.1 STRESS ASSESSMENT OF INDUCTION MOTORS
The concern of motor and equipment manufacturers is excessive mechanical stresses that are
possibly produced when an induction motor is supplied by polluted voltage. It is therefore
important to identify the weakest part of the motor and quantify how much stress it can
tolerate and how much stress is produced by supplying the motor with the voltage resulting
from a power supply disturbance. With these two factors known, an informed decision can
be made on the use of contactor ride-through devices.
The most common area of failure due to excessive mechanical stresses in an induction motor
is the coupling keyway area of the shaft [6]. A determination of the mechanical stresses that
can be tolerated by the coupling key is a good way to determine the stresses that can be
tolerated by the motor, since the coupling keyway area is the weakest part of the machine.
The coupling key prevents the coupling from rotating on the motor shaft and is therefore
responsible for locking the coupling in place so that the torque developed by the motor can
be transmitted to the mechanical load. The coupling key is exposed to any and all torque
transients developed by the motor and transmitted to the load. The torque required to yield
the shaft key can be calculated from
)
(
)
(
)
(
)
(
)
(
in
KeyLength
in
KeyWidth
in
s
ShaftRadiu
psi
gth
YieldStren
lb
in
Torque
×
×
×
=
-
(2.1)
where Torque(in-lb) is the torque in in-lb applied to the motor shaft. From (2.1) it is clear
that the shaft torque is an important measure of mechanical stresses that can be tolerated by
an induction motor.
Chapter 2
Prior Work
Summary :
6 2.1 STRESS ASSESSMENT OF INDUCTION MOTORS The concern of motor and equipment manufacturers is excessive mechanical stresses that are possibly produced when an induction motor is supplied by polluted voltage. The torque required to yield the shaft key can be calculated from ) ( ) ( ) ( ) ( ) ( in KeyLength in KeyWidth in s ShaftRadiu psi gth YieldStren lb in Torque × × × = - (2.1) where Torque(in-lb) is the torque in in-lb applied to the motor shaft.
Tags :
coupling,torque,mechanical,shaft,stresses,key,induction,tolerated,stress,area,load,keyway,part