32 l
Installation, operation and maintenance manual – Squirrel cage motor – WGM20 Line 14108242
6.3.2
Temperatures
The temperatures of the bearings, stator winding and
cooling system must be monitored while the motor is
operating.
These temperatures must stabilize within 4 to 8 hours of
operation.
The stator winding temperature depends on the
machine load; therefore, the driven load must also be
monitored during the motor.
6.3.3
Bearings
The system start, as well as the first hours of operation,
must be monitored carefully.
During the first starting, it is important to pay attention
to unusual vibrations or noises; If the bearing is not
working silently and smoothly, shut the motor down,
identify de cause and correct it;
In case of overheating, the motor must be shut down
immediately for the inspection of bearings and
temperature sensors, and the correction of possible
causes;
After the bearing temperatures stabilize, check if there
are no leaks through the plugs, gaskets or shaft end.
6.3.4
Cooling system
ATTENTION
The motor cannot be operated without water
in the cooling system.
Adjust the water flow and pressure, as indicated on the
plate affixed to the motor;
For operation control purposes, it is recommended that
the cooling water temperatures at the inlet and outlet as
well as the differential pressure at the water inlet and
outlet be measured and recorded periodically;
These values must be periodically compared to the
original value, and an increase in the pressure
differential or a water temperature rise indicates the
need for cleaning the motor water circuit.
6.3.5
Vibration
The motors are balanced at the factory in compliance with
the vibration limits established by IEC60034-14, NEMA
MG1 – Part 7 and NBR 11390 standards (except when
the purchase contract specifies different values).
The vibration measurements are carried out on the NDE
and DE bearings, in the vertical, horizontal and axial
directions. When the customer sends the half coupling to
WEG, the motor is balanced with the half coupling
mounted on the shaft. Otherwise, according to the
standards above, the motor is balanced with half-key (i.e.,
the key slot is filled with a bar of the same width, thickness
and height of the key slot during the balancing operation).
The maximum vibration levels attended by WEG for
motors in operation are informed in Table 6.1. These
values are generic and for guidance, and the specific
application conditions must always be taken into account:
Table 6.1: Vibration (RMS)
Rated speed
(rpm)
Vibration Levels (mm/s RMS)
Frame
< 355 355 to 560
> 630
600 ≤ n ≤ 1800
Alarm
4.5
4.5
5.5
Tripping
7.0
7.0
8.0
1800 < n ≤ 3600
Alarm
3.5
4.5
5.5
Tripping
5.5
6.5
7.5
The main vibration causes are:
Misalignment between the motor and the driven
equipment;
Improper fastening of the motor to the base, with
“loose shims
” under one or more motor feet, and loose
fastening bolts;
Improper or insufficiently rigid base;
External vibrations proceeding from other equipment.
ATTENTION
Operating the motor with vibration levels
above the values contained in may impair its
useful life and/or performance.
6.3.6
Shutdown
In order to shut down the motor, proceed as follows:
Reduce the load of the driven equipment, if possible;
Open the main circuit breaker.
After the motor stops completely:
Shut down the motor cooling water supply system;
Switch on the space heaters. They must be kept ON
until the next motor operation.
DANGER
Even after switching the motor off, while the
rotor is rotating, there is danger to life by
touching any of the motor active parts.
ATTENTION
The terminal boxes of motors equipped with
capacitors must not be opened before the
discharge time.
Discharge time of the capacitors: five
minutes after shutting down the motor.
