32 | Flameproof motors
The alarm and tripping values of the Table 5-5
represent values of permissible shaft vibration for
coupled electric machines. These values are below
ISO 7919-3 Standard.
They are generic values and serve as a guideline,
where specific application conditions must be taken
into consideration, mainly diametric clearance
between shaft and bearing.
Table 5-5 - WEG limits for shaft vibration
Shaft vibration (μm peak to peak)
Operate the motor with shaft
vibration values close to alarm and
tripping values can damage bearing
liners.
The main reasons to cause increase of vibration
are:
- Unbalance coupling problems and others that
can affect the machine;
- Shaft manufacturing problems, which are
minimized during the manufacturing;
- Residual voltage or magnetism on the shaft
surface where measurement is made;
- Scratches, knocks or vibrations when finishing
the shaft where measurement is made.
5.1.9. AUTOMATIC LUBRICATORS
If motor is supplied with motor lubrication it is
mandatory to activate them at start-up.
For details regarding activation of automatic
lubricators refer to sub-section 8.2.9.
ELECTRICAL ASPECTS
5.2.1. POWER SUPPLY
Make sure the motor is connected to the correct
power supply.
Proper electric power supply is very important. All
the wires and protection system must ensure an
excellent quality of electric power supply on the
motor terminals.
The WEG motors are constructed in accordance
with IEC 60034-1 and, unless otherwise stated on
motor data-sheet, they are designed for a rated
voltage of more or less than 10% in relation to rated
value (zone “B” in Figure 5-18).
For rated frequency, a variation of 95% to 103%
(zone “B”) is allowed.
Figure 5-18 - Voltage and frequency variation limits
(IEC 60034-1)
The motor must be able to perfom its main function
(supply torque) continuously at Zone A, but it does
not have to fully meet its performance
characteristics at rated voltage and frequency
(refer to the point with rated characteristics in
Figure 5-18), and it may present some deviations.
The temperature rises values when the motor is
working in the Zone A may be higher than those
obtained at rated voltage and frequency.
The motor must also be able to perform its main
function in Zone B, but it may present greater
deviations of its performance at rated voltage and
frequency than in Zone A. The temperature rises
may be higher than those observed at rated voltage
and frequency and, most likely, will be higher than
those in Zone A.
Prolonged operation in the periphery of Zone B is
not recommended.
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