5. Carefully observe the vibration of the bearing ho using and any abnormal noise generator.
Note that motor vibrat ion may not be identical to t he un coupled values. If cou pled vibration
is excessive, reche c k the mounting and alignmen t.
6. Carefully observe the bearing temperature ris e and the movement of the oil r in g.
If the bearing tempera ture rise and motor oper at ion appear normal, opera tion should con-
tinue until the beari ng t emperatures stabi liz e .
7. If possible, check th e m ot or line currents for bal ance.
It should be rec ognized that ea ch start of an in duction motor su bjects the mot or to full inrush
current with resultin g heating of the stator and r ot or windings. Each acce leration and repeat ed
starts can produc e more heat than is p roduced and di ssipated by the motor under full load. The
starting duty for whic h th e motor is designed is show n by a nameplate mounted on the motor
and must not be exceeded, if long motor life is expecte d. Abnormally low term ina l voltage,
excessive load torqu e and/or excessive load inertia during motor s tart-up can cause leng thened
acceleration times dur i ng which rotor ventilat ion is reduced. This can c au se rotor damage or
can lead to shortened rot or li fe.
The temperature rating of the motor is shown on the mai n na meplate as a temperature rise
above an ambient tempe r at ure. If there is a servic e fa c to r, it is also shown. If the mot or
temperature switch op ens, an investigation s ho uld be made before furt her op eration is
attempted.