6
Installation and maintenance - Three-phase induction motors
4850 en - 2018.11 / f
ASSEMBLY
1.2 - Storage
Prior to commissioning, machines should be stored in a
horizontal position:
- Away from humidity: at relative humidity levels greater than
90% the machine insulation can drop very rapidly, to just above
zero at around 100%. The state of the anti-rust protection on
unpainted parts should be monitored.
For very long storage periods the motor can be placed in a
sealed package (for example heat-shrunk plastic) containing
sachets of desiccant.
- Away from frequent significant variations in temperature, to
avoid the risk of condensation. During storage the drain plugs
must be removed to allow condensation water to escape.
- If the area is subject to vibration, try to reduce the effect of this
vibration by placing the motor on a damping support (rubber
plate or similar) and turn the rotor a fraction of a turn once a
fortnight to prevent the bearing rings from becoming marked.
- Do not discard the rotor locking device (where there are roller
bearings).
Even if the motor has been stored in the correct conditions,
certain checks must be carried out before it is started up:
Greasing
Bearings which cannot be regreased
Maximum storage: 3 years. After this time, replace the bearings
(see section 6.3).
Bearings which can be regreased
Grease
grade 2
Grease
grade 3
Storage
period
less than
6 months
less than
1 year
The motor can be commissioned
without regreasing.
more than
6 months
less than
1 year
more than
1 year
less than
2 years
Regrease before commissioning,
as described in section 3.1
more than
1 year
less than
5 years
more than
2 years and
less than
5 years
Dismantle the bearing
- Clean it
- Replace the grease completely
more than
5 years
more than
5 years
Change the bearing
- Regrease it completely
Greases used by LEROY-SOMER
(see nameplate): - grade 3: ESSO UNIREX N 3
- POLYREX EM103
2 - ASSEMBLY
Electric motors are industrial products.
They must therefore be installed by
qualified, experienced and authorized personnel. The
safety of people, animals and property must be ensured
when fitting the motors into machines (please refer to
current standards).
2.1 - Checking the insulation
Before starting the motor, it is advisable to check
the insulation between the phases and earth,
and between phases.
This check is essential if the motor has been stored for longer
than 6 months or if it has been kept in a damp atmosphere.
This measurement must be carried out using a megohmmeter
at 500V D.C. (do not use a magnetoelectric system).
It is better to carry out an initial test at 30 or 50 volts and if the
insulation is greater than 1 megohm, carry out a second test at
500 volts for 60 seconds. The insulation value must be at least
10 megohms in cold state.
If this value cannot be achieved, or if the motor may have been
splashed with water or salt spray, or kept for a long period in a
very humid place or if it is covered with condensation, it is
advisable to dry the stator for 24 hours in a drying oven at a
temperature of between 110°C and 120°C.
If it is not possible to place the motor in a drying oven:
- Switch on the motor, with the rotor locked, at 3-phase A.C.
voltage reduced to approximately 10% of the rated voltage, for
12 hours (use an induction regulator or a reduction transformer
with adjustable outlets). For slip-ring motors, this test should
be performed with the rotor short-circuited.
- Or supply the 3 phases in series with a D.C. current, with the
voltage at 1 to 2% of the rated voltage (use a D.C. generator
with independent excitation or batteries for motors of less than
22 kW).
- NB: The A.C. current must be monitored using a clamp
ammeter, and the D.C. current using a shunt ammeter. This
current must not exceed 60% of the rated current.
It is advisable to place a thermometer on the motor housing: if
the temperature exceeds 70 °C, reduce the indicated voltage
or current by 5% of the original value for every 10° difference.
While it is drying, all the motor orifices must be open (terminal
box, drain holes).
M
Warning: If the high voltage test, carried out at
the factory before dispatch, needs to be repeated,
it should be performed at half the standard voltage, ie.:
1/2 (2U+1000V). Check that the capacitive effect
resulting from the high voltage test is eliminated before
connecting the terminals to earth.
In all cases, compatibility of the motor and its
environment must be guaranteed before its installation
and also throughout its life.
For all insulation or dielectric tests, it is advisable to
earth the thermal probes and/or accessories.
