Section 12

ELECTRIC MOTORS

GENERAL (field windings) are arranged to produce discreet

north and south magnetic poles when energized.
Industrial facilities may have hundreds of electric Interaction of the magnetic fields produced by
motors of all sizes, types and descriptions. They will the armature and field windings produce a
range in size from sub-fractional horsepower for torque. As the rotor turns the commutator
items such as recorder drives; fractional horsepower switches the current in the rotor windings in a
for small fans, blowers and pumps; integral way to align the magnetic fields so that torque is
horsepower from 1 hp to 250 hp for all types of continuous. The armature and field windings
applications; and up to 10,000 hp for large pumps, may be connected in parallel, series or
fans and motor-generator drives. combinations thereof to produce different
speed/torque characteristics.
Fractional horsepower motors are usually rated 115
volt, single-phase, however, 125 volt DC or 250 volt • AC Induction Motors. These are most often
DC, 208 volt three-phase or 460 volt three-phase designed for operation from a three-phase
may be used for certain applications. source. Single-phase motors are used only in
the smaller sizes, generally less than 1 hp.
BASIC MOTOR TYPES (Single-phase induction motors have no inherent
starting torque and require supplementary
All electric motors consist of a rotating member windings and circuit elements such as capacitors
called the rotor and the stationary member called the during starting.) The three-phase squirrel cage
stator. Both stator and rotor are made up by induction motor is the “work horse of the
stacking thin laminations of steel with special industry” and is a rugged, simple, reliable,
magnetic properties. Windings are placed into slots efficient, low cost driver for many applications.
or on pole pieces of the magnetic cores. All It is basically a constant speed driver. The
windings are insulated except those in the rotors of speed will vary only ½% to 1½% from no-load
squirrel cage induction motors. The design, form to full-load in most applications. The variation
and manner of connecting the windings will may be up to 13% in certain very high starting
determine the basic type of motor. The major types torque designs. The squirrel cage induction
are: motor may be designed for starting torque in the
range of about 50% to 275% of full-load torque.
• DC Motors. DC motors are used where Starting torque may be critical for breaking
interruptions to the AC system would result in loose high friction loads such as conveyors or
undesirable conditions. Examples are - backup for obtaining reasonable acceleration times for
lube oil pumps for large motors, generators or high inertia loads such as large diameter fans.
engines; spring charging motors on circuit Starting current (locked rotor) is usually from
breakers; etc. They are also used where 600% to 700% of full-load current.
specialized torque requirements (high starting
torque) exist for some types of apparatus or The squirrel cage motor is comprised of a stator
where a wide range of speed control is desired. made up from slotted laminations. Insulated
DC motors can be designed for essentially windings are placed in the slots and connected
constant speed applications or variable speed. so that application of a three-phase voltage
The windings on the rotor (armature) are produces a rotating magnetic field. The speed at
brought to a series of copper bars (commutator) which the magnetic field rotates is called
on the periphery of the rotor shaft. Each bar is synchronous speed and is a function of the
insulated from the shaft and adjacent bars. source frequency and the number of pairs of
Spring loaded carbon brushes mounted on a magnetic poles produced by the windings.
stationary support are in electrical contact with Motor no-load speed is very close to
the commutator. The windings on the stator

Rev. 0 Electrical Handbook 12-1

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

synchronous speed. For a 60 hertz source speed, at which time the rotor windings are
frequency: short circuited. For these applications, the
squirrel cage motor may be impractical because
Poles Synchronous Speed of excessive heating resulting from drawing
high starting currents during a long accelerating
2 3600 rpm period. Wound rotor motors are also sometimes
4 1800 rpm used where variable speed is required. They are
6 1200 rpm more expensive than the squirrel cage type and
8 900 rpm somewhat less efficient, especially at speeds
etc. much lower than synchronous speed.

Inside the stator is a cylindrical rotor made of Induction motor stators can also be designed
laminations stacked and secured to the motor with multiple windings for the capability of
shaft. Rotor windings running lengthwise are operating at two or more speeds depending on
placed into slots in the periphery of the rotor. how the windings are connected. The most
These windings may be of uninsulated copper usual speed ratio is 2 to 1, however 3 to 4 or 4 to
bars, short circuited to each other at each end of 1 ratios are obtainable. Connection switching of
the rotor by a brazed copper ring. With some the stator windings is accomplished by multiple
manufacturers, the rotor windings and the contactors in the motor starter.
shorting conductors are aluminum cast into the
rotor. Although rotor currents may be quite • AC Synchronous Motors. These have stators
high, uninsulated rotor windings may be used essentially the same as induction motors.
because the induced voltages are low. The rotor Rotors, however, are wound with insulated
winding configuration resembles a squirrel cage; conductors arranged to produce discrete north
hence the name. The rotating magnetic field and south poles when energized with DC
produced by the stator windings cuts the short voltage. At full speed these rotor fields lock in
circuited rotor bars, inducing electrical currents with the rotating stator fields and the machine
in them which in turn produce a magnetic field. runs at synchronous (constant) speed as
The interaction of the two magnetic fields determined by system frequency and the number
results in a torque causing the rotor to turn. In of pole pairs of the stator winding.
the squirrel cage motor the rotor conductors are
not brought out to any external connection. The Synchronous motors are inherently more
simplicity of the rotor results in the most efficient than induction motors and, in the larger
rugged, dependable and least expensive of all sizes and lower speeds, are lower in initial cost.
motor types for most applications. They can be designed to run at zero or leading
power factor which can be of advantage in
There is another type of induction motor called improving voltage regulation in the power
the “wound rotor” . Here the rotor windings are system. They are most frequently used for large,
insulated and brought out to slip rings on the low-speed pump applications.
motor shaft. Stationary carbon brushes riding
on the slip rings allow connecting the rotor to Starting torque for synchronous motors is
external circuits. By connecting the rotor to provided by embedding short circuited
adjustable resistance a variation of speed/torque conductors in the pole faces of the rotor to form
characteristics is obtained. Starting current is a squirrel cage as in the induction motor.
greatly reduced for high values of rotor During starting the DC winding of the rotor is
resistance. These characteristics are sometimes disconnected from its source and short circuited
of advantage in starting high inertia loads, such which produces additional starting torque. If
as large fans, and bringing them up to full the field winding is left open circuited or

Rev. 0 Electrical Handbook 12-2

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

connected to the DC source while starting, driven equipment. It is not common, but may be
extremely high and possibly damaging voltages found on reciprocating compressor drives.
would be induced. Once the motor is nearly up
to synchronous speed DC excitation is applied to Flange mounted. This is similar to the engine type,
the rotor windings and the machine pulls into but with the stator face bolted directly to a flange on
step. the driven equipment.

The DC source for field (rotor) excitation may Pedestal type. These have a common base to which
be external to the machine and connected by are attached the stator and separate pedestals
means of slip rings and brushes. Used more carrying the rotor bearings. Sometimes used in large
often are shaft mounted SCR rectifiers or silicon low and medium speed applications.
diodes and associated control apparatus supplied
from a shaft driven alternator. This
arrangement eliminates the need for brushes and • Vertical Shaft. Most often used as pump
slip rings. The shaft mounted controls provide drivers.
for connecting a resistor across the field
windings during starting and for automatically Solid shaft. The end of the motor shaft has a keyed,
connecting DC excitation when the machine is flanged coupling bolted to a mating half on the
nearly at full speed. driven equipment. Often the base of the motor stator
is supported by the driven pump. Motor to pump
• Adjustable Speed Synchronous Motors. These distance is short and the pump usually has its own
employ static power conversion systems to thrust and guide bearings.
control the voltage and frequency applied to
brushless synchronous motors in ratings up to Hollow shaft. Here the motor shaft is hollow to
30,000 hp. They are considerably more efficient allow the pump shaft to extend through to the top of
than other forms of speed control and in spite of the motor. The mechanical connection is made at
their high initial cost, may be overall the most the top of both shafts, usually with a nut threaded to
economical driver for large pumps and fans. the pump shaft to allow vertical adjustment of the
pump impeller. It is used for long shafts,
particularly for submerged (deep-well) pumps. The
MOTOR CONFIGURATIONS motor has a thrust bearing to take the weight of the
motor rotor, the pump impeller and shaft, and the
Motors are available in a variety of configurations as hydraulic thrust of the pump.
determined by the driven equipment and application.
The two major configurations are horizontal shaft
and vertical shaft in many variations as follows: MOTOR ENCLOSURES

• Horizontal Shaft. Motor enclosures are principly grouped into two (2)
standardized classifications by NEMA (National
Bracket bearing. This is the most common type Electric Manufacturers Association). These two (2)
with shaft bearings held in end bells or brackets classification groups are Open or Totally enclosed.
attached to the stator. Connection to the driven Enclosure construction offers different degrees of
equipment may be by direct coupling, flex-coupling protection to the operating parts and windings.
or belts. These are used for pumps, fans,
compressors, crane or hoist drives, etc. Open NEMA enclosure classification types

Engine type. There is no motor shaft or bearings. • Drip-proof. This is an open motor, very
The rotor is mounted directly on the shaft of the common in indoor, dry applications and can

Rev. 0 Electrical Handbook 12-3

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

withstand water droplets or particles falling enclosure (frame) number is also identified on the
from 0° to 15° from the vertical. Cooling air is motor data nameplate.
circulated by shaft mounted fan blades.
Openings may be guarded by the addition of MOTOR BEARINGS
screens or baffles.
Bearings are provided to carry radial and thrust
• Splash-proof. This is similar to the drip-proof loads and to hold the rotor centered in the stator.
enclosure except it is designed to protect against Motors used with belt drives may have high radial
entry to droplets or particles falling or splashing loads. Many horizontal motors are designed to take
from 0° to 100° from the vertical. May also be no minimal axial thrust - others may require thrust
guarded. bearings. Vertical motors must have bearings to
accommodate at least the rotor weight and often the
• Open pipe-ventilated. Pipes or ducts from weight of a pump impeller and shaft, and its
another area admit cooling air to the motor. hydraulic thrust. Bearing types are:
Exhaust is to the open space. It may be used in
locations where dirt, dust, or high ambient • Anti-friction. These are ball or roller bearings
temperatures are problems. used often on relatively small horizontal motors
and on small and large vertical motors for radial
• Weather-protected, Type I. Suitable for or thrust loads. They are less often used on
outdoor use. An open motor with ventilating large horizontal motors.
passages designed to minimize entrance of rain, • Sleeve. These are most often used on the larger
snow or dust. horizontal motors and may be of the split or
solid type. Sleeve bearings are frequently
• Weather-protected, Type II. Similar to Type I specified for horizontal motors down to 100 hp
except baffles are designed so that wind driven because failure of roller or ball bearings usually
particles entering the ventilating openings are occurs suddenly resulting in damage to the rotor
discharged without contacting electrical parts. and stator. Sleeve bearings wear gradually and
can be checked periodically.
• Thrust bearings. These are most important on
Totally Enclosed NEMA classification types: vertical motors. They are usually of the roller
type. On very large, high thrust units. pivoted
• Pipe-ventilated. Here both intake and exhaust shoe bearings or plate bearings may be used.
are directed or piped to another area.
Bearing Lubrication and Cooling
• Fan-cooled (TEFC). All electrical parts are
enclosed. An external (to the enclosing parts) Bearing lubrication and cooling can become critical
integral fan draws cooling air over the primary in large motors. Lubrication types are:
enclosure. These also come in explosion proof
versions for use in hazardous atmospheres. • Pre-lubed. These are usually of the anti-friction
type with sealed-for-life lubricant. They are
• Other totally enclosed types include those with most often used on small motors.
separate or integrally mounted air-to-air or air- • Grease-lubed. These also are usually of the
to-water heat exchangers. anti-friction type with a grease fitting for
periodic addition of lubricant. They are used on
NEMA assigns a standardized corresponding larger motors.
enclosure (frame) number to identify specifics • Oil-ring, reservoir. These have one or several
relative to the motor enclosure. This NEMA metallic rings resting on the shaft journal. As
the shaft turns the rings are driven to pick up oil

Rev. 0 Electrical Handbook 12-4

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

from an integral reservoir and deposit it on the ∗ service factor generally only applies to open
journal. These are used on horizontal sleeve motors and allows continuous operation at 115%
bearings in relatively high speed applications. of rating.

• Forced-oil. This also is used with large The various insulation classes are:
horizontal sleeve bearings and sometimes with
plate or shoe thrust bearings. A shaft driven or Class Total Temp. Typical Materials
separately driven pump circulates oil from a
reservoir to the bearing surfaces. A 105°C Usually organic:
• Oil reservoir. Here the oil reservoir is arranges phenolics, enamels, cotton,
so that the oil immerses the bearing. Most silk, varnished paper, etc.
frequently used with large vertical motors for No longer in common use
lubrication of thrust bearings of the anti-friction, in industrial plants.
plate and shoe types.
B 130°C Usually involves mica,
With all oil systems, seals of one type or another are glass, asbestos, and
required to prevent oil leakage into the motor or out synthetic resins.
the shaft. Supplemental cooling may be required for
the larger bearings, particularly thrust bearings. F 155°C Materials vary by
This may take the form of cooling coils immersed in manufacturer. Usually
the oil reservoir or a separate heat exchanger proprietary.
through which the oil is circulated.
H 180°C Materials vary by
manufacturer. Usually
MOTOR INSULATION AND TEMPERATURE RISE proprietary.

Motor electrical losses produce heating which if not Sometimes a tropical treatment is specified to
carried away, will raise winding temperatures to the provide additional protection against moisture,
point where insulation will suffer damage or fungus, insects, etc.
reduction in life. The rule-of-thumb is that for every
8°C to 10°C (46.4°F to 50°F) increase in Many of the newer insulation systems utilizing
temperature, the insulation life is reduced by half. synthetic materials and encapsulation perform
extremely well in hostile environments, some being
Insulation classes are based on total continuous suitable for operation submerged.
conductor operating temperatures which will result
in a reasonable life. Although based on total
temperature the temperature class is usually MOTOR WINDINGS
expressed as the allowable temperature rise above a
40°C (104°F) ambient. The following for Class A There are two general types of windings used in
insulation illustrates this point: motors. These are:

Class A 40°C ambient • Scrambled (or random) wound. These are

40°C temperature rise by used primarily on the smaller motors and are
thermometer made from relatively small diameter round
15°C hot spot allowance copper wire insulated with a coating of enamel
10°C service factor* or synthetic resin. The required number of turns
105°C total temperature are wound into a formed coil to which is applied

Rev. 0 Electrical Handbook 12-5

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

an overall insulation layer before placing the specification) for a particular package or system that
coil into the stator slots. is Vendor pre-assembled, supplied, or provided.
Some (motor driven) mechanical equipment is
• Form-wound. All larger motors have “spec’d” out by the Design Engineer (e.g. MOV
preformed windings. Copper of rectangular motor operated valves, or typical service type pumps)
cross section and with conductor insulation to procure a “bulk” quantity of similar types.
applied is wound on a form. After winding, the Motors are classified as “rotating equipment” and as
coil may be pulled into its final shape, and the such principly fall under dual Field Engineer
slot portion hot molded to better fit the slots. (Mechanical and Electrical) responsibilities. Motors
Additional overall insulation is applied over the are received; either, installed with the servicing
coils which are then placed in the slots and equipment or are shipped loose, requiring field
wedged in place. The coil ends are connected to installation as part of the equipment installation.
each other, insulated and secured. The complete Motors mounted with/or on their associated
stator assembly with windings in place is usually equipment typically include:
then vacuum/pressure impregnated with a
thermo setting synthetic resin. This process • Pump base or Vendor equipment skids.
drives out moisture and solvents, fills all voids • Motorized Doors or equipment hatches.
in the insulation (particularly important for • Motor Operated Valves.
motors 4 kV and above to prevent corona) and • Chemical analyzer or Emissions monitoring
mechanically locks the coils into the slots. systems.
• HVAC - Fans, Blowers, and Dampers.
With the larger medium voltage motors particularly, • Overhead Cranes, Hoists, Elevator Machinery.
all of the above complex operations require highly • Sump, Sewer, Well Pumps.
trained people and carefully controlled materials and
processes. Verification of proper fabrication is Motors (provided by), but requiring specific field
usually done by in-process testing, and dielectric and installation generally include:
performance testing of the completed motor. • Some 480v, most all 2300v or larger motors.
• Chemical Mixers or Injectors.
• M-G sets, Turbines.
ACCESSORIES
Prior to or upon receipt of 480vAC or larger motors,
Many accessories are available for motors of the that are shipped loose, the Electrical Field Engineer
various sizes and types. These include CT’s, surge should ensure the following activities are performed:
suppressers, winding temperature detectors (RTD’s),
bearing thermocouples (TC’s) to name a few. • Establish storage level requirements or if any
Frequently special terminal boxes are required. weather protection is required.
Standard size boxes are often too small for training
• Determine if temporary power or heat is
and terminating the conductors used in industrial
required for applicable motors.
plants which, because of design requirements for
• Perform and record a “megger” test on all 480v
derating, are generally larger than the conductors
or larger motors. Ensure any circuitry that may
used in many standard applications.
be affected by the megger test is determinated.
• Record and/or verify motor nameplate data. A
Motor Procurement, Receiving, and Storage.
manufacturers motor nameplate is a requirement
of the code.
Motors are routinely associated with Mechanical,
Piping, HVAC, and some Instrumentation systems or
The nameplate data should always contain:
components and subsequently are inclusive, as part
• Manufacturer’s name.
of an/the overall Mechanical Purchase Order (or

Rev. 0 Electrical Handbook 12-6

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

• Rated volts and full load amperage for each Motor Terminal Housing.
rated speed.
• Number of phases and rated frequency. Motor terminal housings are typically referred to as
• Rated “full load speed”. (RPM - revolutions per “peckerheads”. These terminal housings are sized
minute). by the motor manufacturer based on code specifics.
• Rated temperature rise, ambient temperature, Unless, the Design Engineer specifically requests for
and insulation class. a “larger housing”, the manufacturer will assume
• Time rating. that the housing size provided will be adequate for
• Horsepower and “locked-rotor amperes”. incoming cable(s) termination. To ensure that the
• Thermally Protected if necessary. manufacturer provided peckerhead(s) is adequate for
raceway, cable, termination, and maintenance
Additional nameplate(s) data includes: accessability the Field Engineer should review the
motor manufacturer’s detail drawing or pump and
• Service Factor. motor layout diagram for the following information:
• NEMA motor (enclosure) frame type.
• Model or Serial number. • Peckerhead size, location, and orientation.
• Identifying Equipment Number. • Peckerhead raceway entrance size and
• Purchase Order or Specification Number. orientation.
• Motor lead designations. • Independent space heater, winding temperature
detector, or bearing thermocouple peckerheads.
• A directional rotation arrow.
Failure to consider the peckerhead orientation, size,
Motor leads must also be “identifiably marked”.
and location generally create the following conflicts:
Motors with multiple leads for various voltage usage
(or with an integral space heater), a nameplate or
diagram identifying which leads are for which • Raceway
desired voltage should also be apart of the motor. • Raceway fed overhead when peckerhead has
bottom feed entrance and is not capable of
Specific motor data, vendor test results, operating being rotated, changed out, or enlarged.
manual, and “performance curves” are also included • Servicing raceway too large or too many for
with the motor “purchase order” documentation. peckerhead entrance cover or opening(s).
• Underground raceway “misses” the
Supplemental instrument devices mounted onto peckerhead box by being on the wrong side
larger motors (e.g. 2300v), or shipped loose include: of motor or stubs up on the wrong end.
• Surge suppressors (CT). • Peckerhead “too low” from ground for
• Winding temperature detectors (RTD). underground feeder raceway and flex.
• Bearing thermocouple (TC). • Peckerhead required to be drilled and
• Vibration sensors or probes (VT). tapped, enlarged, or knocked out to
• Speed sensors or probes (ST). accomodate raceway.

The Field Engineer should inspect the equipment • Cable and Termination
motor (and pump) to ensure these supplemental • Peckerhead too small for motor “splices”.
devices where not damaged during shipment, • Cable too big when raceway is reduced to
storage, transit from storage to installation, or accomodate entrance opening or box size.
equipment motor (or pump) placement. • Servicing cable may be required to be
Too, common to all larger motors (e.g. 2300v), and derated due to size of terminal housing.
some 480v motors, are lifting lugs or eyes mounted • Ground wire must be drilled or tapped.
on the frame.

Rev. 0 Electrical Handbook 12-7

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

• Accessability • Overcurrent or Undervoltage Protection.

• Terminal housing blocked due to • Trip, reset, override, local or remote control.
proximity to walls or other devices, etc,. • Short Circuit or Ground Fault protection.
• Terminal housing access blocked for • Flow, Metering, Measurement Indication.
maintenance access, egress, or safe
working space clearances not maintained. Motor Installation.
• Valve cover blocked by pipe hangers or
other installed devices. Motors mounted on existing piping components (e.g.
MOV’s) are installed by that respective discipline.
Motor Controls and Circuitry. Motors associated with mechanical skids or HVAC
equipment is traditionally installed by the
Essential to all motors are the power, control, and Mechanical department. Some motors, or in other
instrumentation circuitry associated with the motor. instances the motor housing, may be removed to aid
Design drawings detailing these power, control, and in the transportation, alignment, or setting of the
instrumentation motor circuits are: mechanical skid, pump, or equipment frame.
Installation activities associated with removing the
• Vendor wiring diagrams and schematics. motor or housing is performed either with or by the
• Elementries and motor schematics. electricians.
• Cable block diagrams.
• Equipment one-line diagrams. Motors requiring installation (i.e. shipped loose) are
• Loop Drawings and diagrams. installed either by the “millwrights” of the
mechanical department or the electricians dependent
Every motor must have a disconnecting means. on site labor agreements or craft trade jurisdictions
Primary disconnecting means commonly used are: in effect.

• Individual MCC or Rack in Switchgear Breaker Motor location and placement for maintenance
cubicles or compartments. activities that must be considered include:
• Local disconnects, local or remote start-stop
hand or push button stations. • Load and Equipment removal path.
• Breakers, fuses, local controllers. • Temporary or permanent rigging beams or
monorails.
Common low voltage control and DCS (Digital • Overhead congestion, horizontal swing, mobile
Control System) or PLC (Programmable Logic equipment access.
Control) instrumentation circuits and devices
generally used; in conjunction, with the normal Prerequisites before Initial Motor Energization.
function of any equipment motor, are identified on
the P&ID’s relative to that system that the respective Prior to performing an energized test(s) on a motor,
equipments primary service or function is utilized or the motors control circuits, the Field Engineer
for. These control and instrumentation devices should prepare or review a pre-energization check
generally fall into the following “family list that considers or ensures the following:
similarities”:
• Ensure the Motor is Safely Locked and Tagged
• Vibration Monitoring. Out of Service locally and at the primary power
• Speed Control or Sensors. source.
• Thermal, Ambient, or Humidity Control. • All local or remote hand and push buttons
• Position Indication and Alarm. stations are correctly wired per the applicable
• Temperature and Bearing Indication. design schematic or wiring drawings and are
• Torque Control.

Rev. 0 Electrical Handbook 12-8

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

also Safely Locked and Tagged Out of Service cubicle) that the contactor drops in or out upon
and the motor is incapable of an automatic start. actuation.
• Ensure that the Motors power and controls are • Any local or remote start-stop hand or push
terminated at both ends, and is properly button station is wired or designed correctly.
grounded. • Selector switches and contacts are also wired
• Ensure area around motor is “flagged”, roped correctly or device needs replacement.
off, or barricaded restricting personnel access. • Run, Start, and Stop indication lights are wired
• Power cables and motor leads were “meggered” correctly.
and the megohms readings are acceptable and • Resets, emergency stops, vendor wiring at the
were recorded for final documentation and breaker compartment or cubicle is correct.
turnover. Insulation Resistance check should be • Control fuses don’t blow or are missing.
“phase to phase and phase to ground”. • Space heater circuit is functional.
Minimum acceptable readings are usually • The controls portion of the motor schematic.
defined in the project specifications. Motors and
cables rated at (2300v or 4kVA) should always Prerequisites to the performance of this controls test
be meggered with a 5000vDC megger. may require; dependent on test conditions, wiring
schematic, or testing approach, the following:
Note: The initial motor megger that was
performed is generally used to determine if the • Determination of DCS wiring, lifting and
motor is bad upon receipt from supplier. Hence, isolating wires, and adding or jumpering out
it is always good practice to re-megger the points.
motor prior to initial energization. • Temporary control power and if applicable using
the “test” switch circuit at the breaker cubicle or
• Millwrights have uncoupled the motor from the compartment.
drive shaft and it could be freely turned by hand. • Multimeter, fluke, motor schematic, test record.
Motor shaft guard is in place. Millwrights are
complete with any alignments or adjustments Benefits to performing the controls test in advance of
and the motor is “oiled” or “greased” and the motor energization include:
Millwrights have given their authorization to • Troubleshooting problems limited to the control
“run the uncoupled motor”. circuit.
• Communications have been established at: • Local motor start - stop capability proven.
• Motors originating power and control
source location. Motor Rotation Verification.
• Local or remote control hand or push button
stations. After successfully performing or resolving any motor
• DCS (Digital Control System) test console control circuit problems the Field Engineer should
or control room console. next energize the motor and verify that the motor
• Motor location. rotates in the proper direction.

Motor Controls Energized Test. In addition to the pre-check list the Field Engineer
should:
After these pre-checks are accomplished the initial
energized test(s) should be to verify the motors low • Notify all the principle participants that desire to
voltage control circuit(s). This controls test will “witness” this test or those that will be directly
“prove” or accomplish the following: involved with the rotation check that the initial
energization of the motor is to be performed.
• Open or closed contacts are wired or designed • Clear all Locked and Tagged Out Devices.
correctly and (at the breaker compartment or

Rev. 0 Electrical Handbook 12-9

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

Verification of motor rotation either “clockwise or Motor Run-in.

counterclockwise” is more commonly known as
“bumping” the motor. By definition a motor run-in is not bumping the
motor but running the motor without any load for a
Note: Bumping of some motors will have a different predetermined length of time (usually 1 to 2 hours),
desired effect dependent on; equipment function, the to verify the following conditions do not exist before
motor services. Some examples include: the motor is utilized under load or placed into
actual service:
• Fans or blowers - sucking air or exhausting air.
• Valves or Dampers - opens or closes. • Excessive vibration.
• Insufficient lubrication, leaks, or
Bumping the motor should be performed: uncharacteristic noises are detected.
• Cutout, time delays, or thermal protective
• At the primary Power or control source or, overcurrent devices perform or don’t as
• Locally at the hand station. expected.
• Through the DCS test console. • Bearing or winding noises are detected.
• If applicable, at remote panels or consoles. • Noticeable heat or smoke is detected.
• Motor rated speed is exceeded.
If, rotation is reversed from the desired direction
Lock and Tag Out applicable Devices and on a Motor Records and Documentation
three (3) phase motor, switch two (2) phases at the
most convenient end (usually at the breaker), update Motor nameplate data, megger results, rotation or
applicable drawings and documents, and reperform run-in tests performed should be documented,
the bump to verify the direction is now correct. recorded, and verified acceptable and subsequently
“turned over” with the applicable system. In
Performance of a motor bump typically should not addition, the Electrical Field Engineer should notify
last longer than the time it takes to verify or record: or provide the motor documentation to the
Mechanical Field Engineer for incorporation into or
• Correct rotation. to supplement the Rotation Equipment Record(s)
• DCS run or start indication was received. documentation.
• DCS stop indication when motor is deenergized.
• No load starting current, ranges, or curves are Motor Maintenance.
correct or checked.
• Indication lights work as expected. Motor maintenance records of service are performed
by construction up to (motors) equipment turnover to
Deficiencies or failures to receive “expected” results either construction start-up or the clients
will require troubleshooting to resolve and correct. maintenance or start up groups. These records are
The re-performance of the motor bump is, usually, required to ensure that proper maintenance or
required to ensure the problems were corrected. service was performed to maintain equipment
warranty as recommended by the manufacturer.
Note: some 2300v or larger motors may have a Defective motors; not caused by construction misuse,
programmable logic controller at the Medium abuse, failure to maintain proper records and
Voltage Switchgear that may limit the number of storage, or damaged due to testing or installation are
motor starts in a given time frame as one of its “backchargeable” conditions to the vendor or
protective devices. Too, prior to restarting any manufacturer which will authorize repair or
motor, it is sound contruction practice to ensure that replacement of the motor.
the motor has come to a “full stop” and is not “free
wheeling”.

Rev. 0 Electrical Handbook 12-10

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

Vertical mounted motor examples

Rev. 0 Electrical Handbook 12-11

 Bechtel Corporation 1997. 12/2/97
Section 12
ELECTRIC MOTORS

Horizontal mounted motor examples

Rev. 0 Electrical Handbook 12-12

 Bechtel Corporation 1997. 12/2/97