WEG Electric NEMA LOW VOLTAGE ELECTRIC MOTORS Installation Guide
260.03/122002
INSTALLATION AND
MAINTENANCE MANUAL
FOR NEMA LOW VOLTAGE
ELECTRIC MOTORS
TT
The electric motor is the item of equipment most
TT
widely used by man in his pursuit of progress, as
virtually all machines and many renowned inventions
depend upon it.
By virtue of the prominent role the electric motor
plays in the comfort and welfare of mankind, it must
be regarded and treated as a prime power unit
embodying features that merit special attention,
including its installation and maintenance.
This means that the electric motor should receive
proper attention.
Its installation and routine maintenance require
specific care to ensure perfect operation and longer
life of the unit.
THE WEG ELECTRIC MOTOR INST ALLA TION AND
MAINTENANCE MANUAL provides the necessary
information to properly install, maintain and preserve
the most important component of all equipment:
THE ELECTRIC MOTOR!
WEG
Contents
INSTALLATION AND MAINTENANCE MANUAL
FOR NEMA LOW VOLTAGE ELECTRIC MOTORS
1 - Introduction .................................................................. 04
2 - Basic Instructions ........................................................ 05
2.1 Safety Instructions....................................................... 05
2.2 Delivery .................................................................. 05
2.3 Storage .................................................................. 05
2.3.1 Drying the Windings.................................... 06
3 - Installation .................................................................. 07
3.1 Mechanical Aspects.................................................. 07
3.1.1 Foundation ................................................. 07
3.1.2 Types of bases ........................................... 07
3.1.3 Alignment.................................................... 08
3.1.4 Coupling..................................................... 08
3.2 Electrical Aspects...................................................... 16
3.2.1 Feed System .............................................. 16
3.2.2 Starting of Electric Motors ............................ 16
3.2.3 Motor Protection.......................................... 18
3.3 Start-up .................................................................. 18
3.3.1 Preliminary Inspection................................. 18
3.3.2 The First Start-up........................................ 18
3.3.3 Operation ................................................... 18
3.3.4 Stopping ..................................................... 18
4 - Maintenance .................................................................. 23
4.1 Cleanliness.............................................................. 23
4.2 Lubrication............................................................... 23
4.2.1 Periodical Lubrication.................................. 23
4.2.2 Quality and Quantity of Grease.................... 23
4.2.3 Lubricating Instructions................................ 23
4.2.4 Replacement of Bearings ............................ 24
4.3 Air Gap Checking .................................................... 24
4.4 Explosion Proof Motor Repair Steps......................... 24
4.4.1 Objective .................................................... 24
4.4.2 Repair Procedure and Precautions............. 24
4.4.3 Miscellaneous Recommendations................ 25
5 - Malfunctioning .............................................................. 26
5.1 Standard Three-phase Motor Failures ..................... 26
5.1.1 Short Circuits Between Turns...................... 26
5.1.2 Winding Failures ......................................... 26
5.1.3 Rotor Failures............................................. 27
5.1.4 Bearing Failures ......................................... 27
5.1.5 Shaft Fractures ........................................... 27
5.1.6 Unbalanced V-Belt Drives........................... 27
5.1.7 Damage Arising from Poorly Fitted
Transmission Parts or
Improper Motor Alignment ........................... 27
5.2 Troubleshooting Chart ............................................. 28
6 - Spare Parts and Component Terminology ................. 29
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INSTALLA TION AND MAINTENANCE MANUAL
FOR NEMA LOW VOL T AGE ELECTRIC MOTORS
1. Introduction
INSTALLATION AND MAINTENANCE MANUAL
FOR NEMA LOW VOLTAGE ELECTRIC MOTORS
TT
This manual covers all the three-phase and
TT
single-phase asynchronous squirrel-cage
induction motors, from 140T to 580T frame
sizes.
The motors described in this manual are subject
to continuous improvement and all information
is subject to change without notice.
For further details, please consult WEG .
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INSTALLATION AND MAINTENANCE MANUAL
FOR NEMA LOW VOLTAGE ELECTRIC MOTORS
2. Basic Instructions
2.1 Safety Instructions
All personnel involved with electrical installations, either handling,
lifting, operation and maintenance, should be well-informed and upto-date concerning the safety standards and principles that govern
the work and carefully follow them.
Before work commences, it is the responsibility of the person in
charge to ascertain that these have been duly complied with and to
alert his personnel of the inherent hazards of the job in hand.
It is recommended that these tasks be undertaken only by qualified
personnel and they should be instructed to:
· avoid contact with energized circuits or rotating parts,
· avoid by-passing or rendering inoperative any safeguards or
protective devices,
· avoid extended exposure in close proximity to machinery with
high noise levels,
· use proper care and procedures in handling, lifting, installing,
operating and maintaining the equipment, and
· follow consistently any instructions and product documentation
supplied when they do such work.
Before initiating maintenance procedures, be sure that all power
sources are disconnected from the motor and accessories to avoid
electric shock.
Fire fighting equipment and notices concerning first aid should not
be lacking at the job site; these should be visible and accessible at
all times.
2.2 Delivery
Prior to shipment, motors are factory-tested and balanced. They
are packed in boxes or bolted to a wooden base.
Upon receipt, we recommend careful handling and a physical
examination for damage which may have occurred during
transportation.
In the event of damage and in order to guaranty insurance
coverage, both the nearest WEG sales office and the carrier should
be notified without delay.
bearing surfaces thereby removing the protective film that
impedes metal-to-metal contact.
As a preventive measure against the formation of corrosion
by contact, motors should not be stored near machines
which cause vibrations, and every 3 month their shafts
should be rotated manually.
Insulation resistance fluctuates widely with temperature and
humidity variations and the cleanliness of components. When a
motor is not immediately put into service it should be protected
against moist, high temperatures and impurities, thus avoiding
damage to insulation resistance.
If the motor has been in storage more than six month or has been
subjected to adverse moisture conditions, it is best to check the
insulation resistance of the stator winding with a megohmeter.
If the resistance is lower than ten megohms the windings should be
dried in one of the two following ways:
1) Bake in oven at temperatures not exceeding 194 degrees F
until insulation resistance becomes constant.
2) With rotor locked, apply low voltage and gradually increase
current through windings until temperature measured with
thermometer reaches 194 degrees F . Do not exceed this
temperature.
If the motor is stored for an extensive period, the rotor must be
periodically rotated.
Should the ambient conditions be very humid, a periodical
inspection is recommended during storage. It is difficult to prescribe
rules for the true insulation resistance value of a machine as
resistance varies according to the type, size and rated voltage and
the state of the insulation material used, method of construction and
the machine’s insulation antecedents. A lot of experience is
necessary in order to decide when a machine is ready or not to be
put into service. Periodical records are useful in making this
decision.
The following guidelines show the approximate values that can be
expected of a clean and dry motor, at 40°C test voltage in applied
during one minute.
2.3 Storage
Motors should be raised by their eyebolts and never by their
shafts. It is important that high rating three-phase motors be raised
by their eyebolts. Raising and lowering must be steady and joltless,
otherwise bearings may be harmed.
When motors are not immediately installed, they should be stored in
their normal upright position in a dry even temperature place, free
of dust, gases and corrosive atmosphere.
Other objects should not be placed on or against them.
Motors stored over long periods are subject to loss of insulation
resistance and oxidation of bearings.
Bearings and lubricant deserve special attention during
prolonged periods of storage. Depending on the length
and conditions of storage it may be necessary to regrease
or change rusted bearings. The weight of the rotor in an
inactive motor tends to expel grease from between the
Insulation resistance Rm is obtained by the formula:
Rm = Vn + 1
Where: Rm - minimum recommended insulation resistance in
MΩ with winding at 40°C
Vn - rated machine voltage in kV
In case the test is carried out at a temperature other than 40°C, the
value must be corrected to 40°C using an approximated curve of
insulation resistance v.s temperature of the winding with the aid of
Figure 2.1; it’s possible verify that resistance practically doubles
every 10°C that insulating temperature is lowered.
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INSTALLA TION AND MAINTENANCE MANUAL
FOR NEMA LOW VOL T AGE ELECTRIC MOTORS
Example:
Ambient temperature = 50°C
Motor winding resistence at 50°C = 1.02 MΩ
Correction to 40°C
R
= R
40°C
R
= 1.02 x 1.3
40º C
R
40º C
x K
50°C
= 1.326 MΩ
50°C
The minimum resistence Rm will be:
Rm = Vn + 1
Rm = 0.440 + 1
Rm = 1.440 MΩ
On new motors, lower values are often attained due to solvents present
in the insulating varnishes that later evaporate during normal operation.
This does not necessarily mean that the motor is not operational,
since insulating resistance will increase after a period of service.
On motors which have been in service for a period of time much
larger values are often attained. A comparison of the values recorded
in previous tests on the same motor under similar load, temperature
and humidity conditions, serves as a better indication of insulation
condition than that of the value derived from a single test. Any substantial
or sudden reduction is suspect and the cause determined and
corrective action taken.
Insulation resistance is usually measured with a MEGGER.
In the event that insulation resistance is inferior to the values derived
from the above formula, motors should be subjected to a drying process.
2.3.1 Drying the windings
This operation should be carried out with maximum care, and only by
qualified personnel. The rate of temperature rise should not exceed
5°C per hour and the temperature of the winding should not exceed
105°C. An overly high final temperature as well as a fast temperature
increase rate can each generate vapour harmful to the insulation.
T emperature should be accurately controlled during the drying process
and the insulation resistance measured at regular intervals.
During the early stages of the drying process, insulation resistance
will decrease as a result of the temperature increase, but the resistance
will increase again when the insulation becomes dryer.
The drying process should be extended until sucessive measurements
of insulation resistance indicate that a constant value above the minimum
acceptable value has been attained. It is extremely important that the
interior of the motor be well ventilated during the drying operation to
ensure that the dampness is really removed.
Heat for drying can be obtained from outside sources (an oven),
energization of the space heater (optional), or introducing a current
through the actual winding of the motor being dried.
Figure 2.1
Winding T emperature (ºC)
R
= Rt x K
40 ºC
t 40 ºC
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3. Installation
INSTALLATION AND MAINTENANCE MANUAL
FOR NEMA LOW VOLTAGE ELECTRIC MOTORS
Electric machines should be installed in order to allow an easy access
for inspection and maintenance. Should the surrounding atmosphere
be humid, corrosive or contain flammable substances or particles, it is
essential to ensure an adequate degree of protection.
The installation of motors in environments where there are vapours,
gases or dusts, flammable or combustible materials, subject to fire or
explosion, should be undertaken according to appropriate and
governing codes, such as NEC Art. 500 (National Electrical Code)
and UL-674 (Underwriters Laboratories, Inc.) Standards.
Under no circumstances can motors be enclosed in boxes or covered
with materials which may impede or reduce the free circulation of
ventilating air. Machines fitted with external ventilation should be at
least 50cm from the wall to permit the passage of air.
The opening for the entry and exit of air flow should never be
obstructed or reduced by conductors, pipes or other objects.
The place of installation should allow for air renewal at a rate of 700
cubic feet per minute for each 75 HP motor capacity .
3.1 Mechanical Aspect s
3.1.1 Foundation
The motor base must be levelled and as far as possible free of
vibrations. A concrete foundation is recommended for motors over
100 HP . The choice of base will depend upon the nature of the soil at
the place of erection or of the floor capacity in the case of buildings.
When dimensioning the motor base, keep in mind that the motor may
occasionally be run at a torque above that of the rated full load torque.
Based upon Figure 3.1, foundation stresses can be calculated by
using the following formula:
Where:
F1 and F2 - Lateral stress (Lb)
g - Force of gravity (32.18 ft/s2)
G - Weight of motor (Lb)
Tmax - Maximum torque (Lb . Ft)
A - Obtained from the dimensional drawing of the motor (in)
Sunken bolts or metallic base plates should be used to secure the
motor to the base.
3.1.2 Types of Bases
a) Slide Rails
When motor drive is by pulleys the motor should be mounted on
slide rails and the lower part of the belt should be pulling.
The rail nearest the drive pulley is positioned in such a manner that
the adjusting bolt be between the motor and the driven machine.
The other rail should be positioned with the bolt in the opposite
position, as shown in Figure 3.2.
The motor is bolted to the rails and set on the base. The drive
pulley is aligned such that its center is on a plane with the center of
the driven pulley and the motor shaft and that of the machine be
parallel.
The belt should not be overly stretched, see Figure 3.11.
After the alignment, the rails are fixed.
F1 = 0.2247 (0.009 x g x G - 213 Tmáx/A)
F2 = 0.2247 (0.009 x g x G + 213 Tmax/A )
Figure 3.1 - Base stresses
Figure 3.2 - Positioning of slide rails for motor alignment
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INSTALLA TION AND MAINTENANCE MANUAL
FOR NEMA LOW VOL T AGE ELECTRIC MOTORS
b) Foundation Studs
Very often, particularly when drive is by flexible coupling the motor is
anchored directly to the base with foundation studs.
It is recommended that shim plates of approximately 0.8 inches be
used between the foundation studs and the feet of the motor for
replacement purposes. These shim plates are useful when exchanging
one motor for another of larger shaft height due to variations allowed
by standard tolerances.
Foundation studs should neither be painted nor rusted as both interfere
with to the adherence of the concrete, and bring about loosening.
After accurate alignment and levelling of the motor, the foundation
studs are cemented and their screws tightened to secure the motor.
Thus, simultaneous readings are possible and allow for checking for
any parallel (Figure 3.6a) and concentricity deviations (Figure 3.6b)
by rotating the shafts one turn.
Gauge readings should not exceed 0.02 inches. If the installer is
sufficiently skilled, he can obtain alignment with feeler gauges and a
steel ruler, providing that the couplings are perfect and centered Figure 3.6c.
Figure 3.6a - Deviation
from parallel
Figure 3.6b - Deviation from
concentricity
Figure 3.3 - Motor mounted on a concrete base with foundation
studs
3.1.3 Alignment
The electric motor should be accurately aligned with the driven
machine, particularly in cases of direct coupling. An incorrect alignment
can cause bearing failure vibrations and even shaft rupture.
The best way to ensure correct alignment is to use dial gauges placed
on each coupling half, one reading radially and the other exially Figure 3.5.
Figure 3.6c - Alignment
with a steel ruler
3.1.4 Coupling
a) Direct Coupling
Direct coupling is always preferable due to its lower cost, space
economy, no belt slippage and lower accident risk.
In the case of speed ratio drives, it is also common to use a direct
coupling with a reducer (gear box).
CAUTION: Carefully align the shaft ends using, whenever feasible, a
flexible coupling.
Figure 3.5 - Alignment with dial gauges
8
Figure 3.7 - A type of direct coupling
b) Gear Coupling
Poorly aligned gear couplings are the cause of jerking motions which
bring about the vibration of the actual drive and vibrations within the
motor.
INSTALLATION AND MAINTENANCE MANUAL
FOR NEMA LOW VOLTAGE ELECTRIC MOTORS
Therefore, due care must be given to perfect shaft alignment: exactly
parallel in the case of straight gears, and at the correct angle for bevel
or helical gears.
Perfect gear engagement can be checked by the insertion of a strip of
paper on which the teeth marks will be traced after a single rotation.
c) Belt and Pulley Coupling
Belt coupling is most commonly used when a speed ratio is required.
Assembly of Pulleys: T o assemble pulleys on shaft ends with a keyway
and threaded end holes the pulley should be inserted halfway up the
keyway merely by manual pressure.
On shafts without threaded end holes the heating of the pulley to about
80°C is recommended, or alternatively, the devices illustrated in Figure
3.8 may be employed.
Figure 3.8 - Pulley mounting device
RUNNING: To avoid needless radial stresses on the bearings it is
imperative that shafts are parallel and the pulleys perfectly aligned.
(Figure 3.10).
Figure 3.10 - Correct pulley alignment
Laterally misaligned pulleys, when running, transmit alternating knocks
to the rotor and can damage the bearing housing. Belt slippage can
be avoided by applying a resin (rosin for example).
Belt tension should be sufficient to avoid slippage during operation
(Figure 3.11).
Pulleys that are too small should be avoided; these cause shaft flexion
because belt traction increases in proportion to a decrease in the
pulley size. T able 1 determines minimum pulley diameters, and T ables
2 and 3 refer to the maximum stresses acceptable on motor bearings
up to frame 580. Beyond frame size 600, an analysis should be
requested from the WEG engineering.
Figure 3.8a - Pulley extractor
Hammers should be avoided during the fitting of pulleys and
bearings. The fitting of bearings with the aid of hammers leaves
blemishes on the bearing races. These initially small flaws increase
with usage and can develop to a stage that completely impairs the
bearing.
The correct positioning of a pulley is shown in Figure 3.9.
Figure 3.9 - Correct positioning of pulley on the shaft
Figure 3.1 1 - Belt tensions
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INSTALLA TION AND MAINTENANCE MANUAL
FOR NEMA LOW VOL T AGE ELECTRIC MOTORS
T able 1 - Minimum pitch diameter of pulleys
Ball bearings
Frame Size X Inches
140 6205-Z 1.7 1.85 2
W 180 6206-Z 3.03 3.23 3.46
180 6307-Z 1.69 1.81 1.93
W 210 6308-Z 2.86 3.00 3.16
210 6308-Z 2.90 3.06 3.22
W 250 6309 C3 4.37 4.54 4.72 4.92
25 0 6309 C3 4.41 4.59 4.77 4.97
280 6311 C3 5.08 5.19 5.47 5.65
32 0 6312 C3 7.44 7.76 7.94 8.18
36 0 6314 C3 8.73 9.00 9.28 9.57
Frame Poles Size X Inches Size X Inches
400
440
500
5008
580
Bearing
II 6314 C3 7.3 7.62 7.94 8.24 - - - - - -
IV-VI-VII 6314 C3 NU 316 4.13 4.31 4.49 4.67 4.85 -
II 6314 C3 1 1.75 12.16 12.61 13.08 - - - - - -
IV-VI-VIII 6319 C3 NU 319 4.02 4.17 4.32 4.47 4.62 4.82
II 6314 C3 23.54 24.34 25.12 25.87 - - - - - -
IV-VI-VIII 6319 C3 NU 319 6.52 6.73 6.95 7.17 7.39 7.67
II 6314 C3 44.66 45.79 46.98 48.23 - - - - - -
IV-VI-VIII 6322 C3 NU 322 8.73 8.95 9.96 11.34 12.87 14.82
II 6314 C3 5 7 5 8 5 9 6 0 - - - - - -
IV-VI-VIII 6322 C3 NU 322 10.72 10.91 11.1 1 11.31 11.50 1 1.76
0.79 1.57 2.36 3.15 3.94 4.72
Ball Bearing Roller Bearing
Bearing Bearing
1.97 3.15 4.33 5.51 1.97 3.15 4.33 5.51 6.69 8.27
Important: 1) Peripheral speeds for solid grey cast iron pulleys FC 200 is V = 1 15 ft/s.
2) Use steel pulleys when peripheral speed is higher than 115 ft/s.
3) V-belt speed should not exceed 1 15 ft/s.
T able 2 - Maximum acceptable radial load (Lbf)
Nema 56 Motors Saw Arbor Motors
Radial Force (Lbf) 80 LMS II - 35 5 -
Frame Distance X 80 MMS II - 3 59 -
56A 90 LMS
56B
56D
Poles
II 88 - 59 II 427 -
IV 88 - 59 IV - 555 -
II 88 - 59
IV 86 - 59
II 127 - 70
IV 141 - 70
1 1,18 2 80 S MS I I - 357 -
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INSTALLATION AND MAINTENANCE MANUAL
FOR NEMA LOW VOLTAGE ELECTRIC MOTORS
T able 3 - Maximum acceptable axial load (Lbf)
IP55 T otally Enclosed Motors - 60Hz
Position / Construction Form
F
R
A
M
E
II IV VI VIII II IV VI VIII II IV VI VIII II IV VI VIII
140 103 141 167 187 112 152 185 207 99 132 158 178 105 143 174 198
W 180 108 145 180 202 154 209 255 286 94 130 165 183 141 194 240 269
180 149 207 249 286 269 370 443 500 136 189 229 266 253 352 421 480
W 210 196 264 326 368 329 447 544 610 176 238 297 339 310 421 518 582
210 189 257 315 357 324 443 533 599 160 220 275 310 295 405 493 553
W 250 282 372 443 485 471 620 734 811 240 317 394 414 430 564 685 743
250 273 368 436 485 463 615 727 813 220 310 379 421 410 557 672 749
280 355 480 551 624 621 826 959 1,082 275 388 427 502 540 736 838 961
320 374 498 588 668 703 930 1,091 1,232 266 366 432 511 597 793 937 1,078
360 890 1,181 1,144 1,323 890 1,181 1,375 1,552 745 985 1,144 1,323 745 985 1,144 1,323
400 877 1,148 1,347 1,521 877 1,148 1,347 1,521 705 890 1,060 1,241 705 890 1,060 1,241
440 842 1,303 1,563 1,821 842 1,303 1,563 1,821 568 884 1,109 1,488 568 884 1,109 1,488
500 769 1,250 1,481 1,728 769 1,250 1,481 1,728 355 721 844 1,190 355 721 844 1,109
5008 791 1624 1909 2137 791 1624 1909 2137 728 1548 1808 2029 728 1548 1808 2029
580 679 1,406 1,649 1,865 679 1,406 1,649 1,865 033 474 549 597 033 474 549 597
Open Motors - NEMA 56 Frames - 60Hz
Position / Construction Form
F
R
A
M
E
II IV II IV II IV II IV
56 A 68 90 83 112 63 85 79 108
56 B 66 90 81 110 63 83 77 105
56 D 63 88 105 145 59 81 101 138
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