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THREE-PHASE ASYNCHRONOUS MOTORS AND GENERATORS
General safety warning. Electric motors are com-
ponents with dangerous parts as they are live or
have parts which move while in operation. There-
fore, incorrect use, removal of protections without
isolating the power supply, disconnection of pro-
tection devices, failure to perform inspections or
maintenance, may cause serious injuries to people
or things. It is recommended that any intervention
on electric machines is carried out by qualified staff
(refer to IEC 364). The following instructions are for
guidance only: always refer to the project documen-
tation - if available - and contact ELECTRO ADDA in
case of doubt. ELECTRO ADDA must be immediately
informed of any problem that is not contemplated by
these instructions.
Operating and maintenance instructions.
The purpose of these instructions is to give the installers and
users correct operating and maintenance conditions concern-
ing asynchronous three-phase motors with enclosed con-
struction, external ventilation and squirrel cage rotor.
For further information refer to the project documentation, if
available, or ask ELECTRO ADDA.
Receipt and storage.
Every motor is dispatched from the factory ready for instal-
lation, after quality control during manufacture as well as
a final test, that is to verify if the motor is in accordance
with all required standards. On receipt, it is recommended
to inspect it to find out whether it has got damages during
transportation. Should the motor not be installed immedi-
ately, it should be kept indoor, in a clean, dry and vibration-
less place. It is advisable to feed the space heaters if they are
available. Approximately every 3 months it is necessary to
turn the shaft 20-30 times and position it at 90° compared
to the previous position to distribute the grease in the rolling
elements. If the machine is stored for more than 3-5 years,
it is necessary to replace the grease (lubricated bearings) or
the bearings (sealed version).
Installation.
Set up the motor in a well cooled place. Care should be taken
to assure that cooling is not hindered by any walls or other
machines next to it. Installation of the motor must occur
according to mounting position for which it has been de-
signed. The possibility of inspections and maintenance when
operating is to be considered. The motor foundation should
be even, solid in order to absorb vibrations, and sufficiently
rigid in order to keep alignment.
Alignment.
The motor must always be carefully aligned, particularly
when coupled direct to the driven machine. Should any
vibrations or bearing failures be observed, check the align-
ment immediately, as it might be faulty.
Couplings.
Output transmission to the driven machine may be provided
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by either direct coupling or by driving belts. In case of a di-
rect coupling, a flexible coupling is to be used, which avoids
any transmission of axial thrusts on the bearings. In case of
coupling by driving belts, set up the motor with shaft parallel
to that of the driven machine and on belt tensioning slides, in
order to adjust belt tension. An excessive belt tension might
cause the bearings to wear out quickly and, in most serious
cases, the shaft to break.
Balancing and installation of couplings and pulleys.
Any different indications excepted, the rotor is dynamically
balanced by a half-key in the free shaft end. The maximum
vibration levels are given in table 8.Carefully balance the
transmission by a half-key before fitting. Couplings and pul-
leys are to be fitted with greatest care, in order to avoid any
impacts which may damage the bearings.
Insulation test.
Before starting the motor and after long periods of inactivity
or storage, the insulation resistance of the winding is to be
measured: it should be higher than 5 M Ω at 25°C ambient
temperature. If this value cannot be obtained, the winding
may be damp and must be dried by a skilled company.
Electric connection.
As to the electric connection, the safety ruling standards are
to be complied with. Check that data on the plate are ac-
cording to the circuit features, to which the motor is to be
connected. Connect according to wiring diagrams 1,2,3,4,5.
Earthing.
Inside the terminal box or next to it, it is connected, in a vis-
ible position, a terminal for earthing the motor, this operation
should be done by means of a copper lead with adequate
section according to the ruling standards.
Direction of rotation.
Standard motors can indifferently run in both rotation direc-
tions. If terminals U1 V1 W1 are connected to the mains and
if the connecting phase sequence of the mains is 1,2,3, the
motor runs clockwise, if seen from the driving end. The rota-
tion direction can by reversed by exchanging any two of three
leads which are connected to the motor.
Electric protections.
Motors must be protected against any consequences of short
circuits, of operating overloading, of single-phase running,
by installing before them a suitably sized switch that must be
provided with a temperature relay and calibrated for the rated
current. In order to increase the operating safety in case of
particularly heavy duties, temperature sensors may be in-
stalled in the windings, upon request: Klixon, PTC Thermis-
tors, Pt100 Heating measuring elements.
Starting the motor.
In the majority, asynchronous three-phase motors with
squirrel cage rotor can be operated with direct starting,
checking the plant according to the absorbed current at the
start. Star-delta connection is to be used when very low start-
ing torques and currents are required, that is 25%-30% of
Electro Adda S.p.A. MM-GEN - Rev. 4-01-2019-IEDFS
the values it would have in case of direct-on-line starting.
When starting the stall torque is to be sufficiently lower than
the starting torque. The commutation from star to delta is
to be converted approaching the rated speed. Should such
conditions not take place, starting is to be done by reducing
the voltage on the motor terminals by transformer, resistors
or stator reactors. In this way a reduction of the torque curve
by the voltage square and of the current curve in accordance
with the voltage can be obtained.
Maintenance.
The motor as well as the possible accessories should always
be kept clean, free of dust traces, dirt, oil or other grime. As
a good rule it is recommended to periodically check whether
the motor operates without any vibrations or anomalous
noises, the tension of possible driving belts is correct, the
inlet of the ventilation circuit is not obstructed causing
overheating of the windings. Contact ELECTRO ADDA for
detailed plans.
Bearings - Lubrication.
Motors with staunch bearings, that are self-lubricating for
life, do not require any lubrication. Bearings life vary from
3 up to 5 years according to the axial and radial loads that
are charged on the shaft and to the environmental condi-
tions the motor is used in. Motors provided with the bear-
ings lubrication device are to be lubricated while running
according to the lubricating intervals, the grease type and
quality as per table 7 and 7a. The lubricating intervals apply
to a motor set up in normal surrounding. If the environmen-
tal conditions are particularly severe owing to dust, water,
high temperatures, the intervals are to be reduced. Table 6
and 6a shows bearings mounted on normal standard mo-
tor types. Pages 22-23-24-25 show the spare parts for the
different normal standard motor types. Should problems in
connection with operating and maintenance of the electric
machines arise, please contact ELECTRO ADDA Engineer-
ing Service.
Inverter supply.
If the motors are supplied by inverter, attention should be
paid in particular to:
• The maximum value of dV/dt at the motor terminals to
be 2000 V/µsec
• The maximum cable length between the inverter and the
motor not to exceed 50m. For values higher than the above, it
is necessary to put an appropriate filter between the motor and
the inverter to reduce stresses on the motor.
For motors with forced ventilation (IC 416) connect the ven-
tilator to the mains supply and make sure it works regularly
(voltage and mains frequency, direction of rotation of the ven-
tilator), during the operation of the asynchronous motor.
If the motor is provided with encoder, make sure that it is
properly connected to the inverter, using appropriate cables.
In case of doubt ask advice to the inverter manufacturer or
contact ELECTRO ADDA.
Electro Adda S.p.A. MM-GEN - Rev. 4-01-2019-IEDFS
Smoke motors.
S series motors are similar to the C series ones concerning
construction, with the exception of materials. In particular,
insulation system and bearings are special: apply to ELEC-
TRO ADDA for details.
Brakes.
If the motors are equipped with brake, pay attention that the
brake supply is according to the data mentioned in the name
plate. If necessary, contact ELECTRO ADDA for additional
information related to brakes.
Water cooled motors.
Make sure that the cooling fluid is according to the values
mentioned in the motor name plate. If necessary, contact
ELECTRO ADDA to obtain the relevant instructions for water
cooled motors.
Three-phase asynchronous generators.
Refer to the project documentation and, if necessary, contact
ELECTRO ADDA to obtain the relevant instructions for asyn-
chronous three-phase generators.
Complete manuals can be requested to the ELECTRO
ADDA Sales Office.
REMARK: in case of doubt or need for clarification
refer to the project documentation, if available, or
contact ELECTRO ADDA.
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