Teco Installation and Maintenance Manual
TEFC Squirrel Cage Induction Motors
Teco Electric and Machinery Company
Manual Number: IOM ~ TEFC Rev.01
17
Chapter 4: OPERATING INSTRUCTIONS
4.1.
EXAMINATION BEFORE START.
4.1.1.
After motor is installed the following points should be noted:-
a.
Check all wiring is correct and in accordance with connections appropriate to the
supply voltage as shown on motor nameplate.
b.
Is the incoming cable size adequate?
c.
Are all connections tight and properly insulated?
d.
Check the rating of fuses, starter/contactor are correct & operating normally.
e.
Check motor is correctly earthed especially if supplied via a VVVF drive.
f.
Make sure starter/switches are set in correct position.
g.
Check heater circuit if fitted is de-energised when motor is in operation.
h.
Check bearings are filled with the correct quantity and grade of grease.
4.1.2.
Measurement of insulation resistance.
a.
Rated voltage below 1000V, measure with 500VDC megger.
b.
In accordance with IEEE-43 clause 9.3 standards, refer to following formula:
R (M
) = > (Rated Voltage + 1) x 10
1000
c.
If a new winding has a low insulation resistance reading moisture ingress is
generally the problem. Drying the winding through the proper application of
heat will normally increase the insulation resistance to an acceptable level.
Following are several accepted methods for applying heat to a winding:
i.
If the motor is equipped with anti condensation heaters these can be can be
energised to heat the winding.
ii. Direct current (as from a DC welder) can be passed through the winding. The
total current should not exceed approximately 50% of rated full load current.
Delta wound motors have six leads and the three phases should be connected
into one series circuit.
iii. Heated air can be either blown directly into the motor or into a temporary
enclosure surrounding the motor. The source of heated air should preferably
