Flameproof motors | 13
VERTICAL MOTORS STORAGE
Vertical motors should be stored in the position as
they were initially transported. Usually they can be
stored in vertical or horizontal position but this
needs always to be prior validated with WEG
Service Team.
OTHER CARES DURING
STORAGE
For motors fitted with space heaters, these
accessories must be kept switched-on.
If painting has suffered any damage, this must be
repainted to avoid rusting. The same applies to the
machined surfaces when protecting grease has
been wasted.
INSULATION RESISTANCE
EX ATMOSPHERE INFORMATION
Be sure that no potentially explosive
atmosphere is present before any
measuring of Insulation Resistance.
Before measuring insulation
resistance, the machine must be at
standstill and all windings and frame
must be grounded for a time to
remove all residual electrostatic
charge (connect all winding to the
frame and this one to the ground).
Capacitors (if any) must also be
grounded before disconnecting and
separating the terminals to measure
the insulation resistance.
The non observation of these
precautions may result in injury to
personnel.
When a motor is not immediately installed, it should
be then protected against moisture, heat and dirt so
as to avoid deterioration of the insulation. The
winding insulation resistance must be measured
before operating the motor.
If the ambient contains high humidity, a periodical
inspection is recommended during storage. It is
difficult to determine rules for the actual insulation
resistance value of a motor as the resistance varies
according to type, size, rated voltage, condition of
the insulating material used and method of
construction of the motor. A lot of experience is
required to decide when a motor is ready for
operation. Periodical records will help to take such
decision.
Disconnect motor from power supply
before making any insulation
measurement.
The insulation resistance should be measured using
a Megohmmeter. The test voltage for the motors
windings should be according the table below in
accordance with the standard IEEE 43.
Table 3-1 – Insulation resistance test voltage
Winding rated voltage
(V)
Insulation resistance test
direct voltage (V)
The test voltage for space heaters, other
accessories and thermal protectors is 500Vcc.
If the test is performed at a different temperature, it
is necessary to correct the resistance reading to
40ºC by using an insulation resistance variation
curve in relation to temperature, given by the motor
itself. If this curve is not available it is possible to use
an approximate correction given by the curve of
Figure 3-1, as per IEEE 43 Standard.
Figure 3-1 – Insulation resistance variation with
temperature
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