Motor Nameplate Handout
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Transcript of Motor Nameplate Handout
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MOTOR NAMEPLATE INFORMATION
The motor nameplate is a description from the manufacturer listing specific information about the
motors characteristics.
Motor standards require motors to be shipped with a nameplate when new.
The National Electrical Code requires specific items on a motor nameplate including:
manufacturer, voltage, full load amps, frequency, phase, RPM, temperature rise or insulation
class and ambient temperature, duty rating, rated horsepower, and locked rotor design letter.
Additional information will normally appear including service factor, enclosure type, frame
size, connection diagrams, and other unique or special features.
ELECTRIC MOTOR NAMEPLATE
MODEL 500 SPLIT PHASE TOTALLY ENCLOSED
FRAME TYPE INS. CLASS IDENTIFICATION NO.
145 KC J 2538094990298209
HP RPM VOLTS AMPS CYC S.F.
1 1725 115/230 15/7.5 60 1.25
DESIGN CODE: B PHASE EFF p.f.
DRIVE END BEARING BBD 116 1 62% 75%
OPP. END BEARING B0B 117 DUTY: CONTINUOUS
AMB 40 C NO THERMAL PROTECTION
Manufacturer's Name, Model, & Serial #The manufacturer's name identifies the manufacturer of the motor.
Model number identifies the model of the motor produced by the specific manufacturer.
Serial number is specific for the manufacturer and identifies the specific motor and is useful
in establishing the age of the motor for replacement parts and warranties.
Motor Type
Identifies the type of motor/generally describes the starting method including:
DC Motors: Shunt Wound, Series Wound, Compound Wound, Permanent Magnet, Universal
Single Phase Motors: Split Phase, Shaded Pole, Permanent Split Capacitor, Capacitor Start,
Capacitor Start-Capacitor Run, Universal.
Three Phase Motors: Squirrel Cage Induction, Wound Rotor, Synchronous, Reluctance
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NEMA Frame Size Designation
NEMA has assigned a series of standardized numbers
and letters to describe various dimensions and
mounting types of motor frames.
When changing a motor, selecting the same
frame size regardless of manufacturer ensures
the mounting mechanism and hole positions
will match.
As a general rule, as frame size increases, so
does physical size and horsepower of the motor.
There are many motors of the same horsepower and size built with different frame sizes so
they can be mounted in various manners.
NEMA Frame Designations
The standard NEMA Frame Size designation may contain:
a prefix of letters
the frame number
a suffix of letters
Frame Size Prefix
Letters or numbers appearing in front of the NEMA Frame Designation are the manufacturers.
They are not standardized within the NEMA designation and importance/meaning varies by
manufacturer.
Example: EF56C
The EF in the frame Designation EF56C is a manufacturers prefix indicating something
about the particular motor compared to other models produced by the same manufacturer.
Frame Size Number
In any standard frame number designation there are either two or
three numbers.
Two Digit Frame Size- Indicates a fractional horsepowermotor less than 1 horsepower.
If the nameplate displays a two digit frame number, the
number is the distance from the center of the drive shaft to
the center bottom of the mount in sixteenths of an inch.
Example: EF56C > 56 divided by 16 = 3.5 inches from shaft to mount.
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S Three Digit Frame Size- indicates an integral horsepower motor 1 horsepower or greater.
For three digit frame sizes, divide the first two digits by four
to calculate the distance from the center of the drive shaft to
the center bottom of the mount in fourths of an inch.
Example: EF145C, > 14 divided by 4 = 3.5
inches from shaft to
mount.
The third digit is an indication of the distance between the
mounting holes parallel to the base.
Example: EF145C, > Mounting holes are 5 inches apart.
Frame Size Suffix
The suffix letter in the frame designation indicates the mounting type of the motor.
Today, new motors are designated "T" frame motors.
Between 1952 and 1964, the NEMA standards designated motors as "U" frame motors.
Prior to 1952, the "Original" standard was used.
Example: 143TD, > A current T-Frame motor using a D-Flange mount.
S No suffix or a T indicates a NEMA standard shaft
For motors that have a letter following the T:
S S indicates a NEMA standard "short shaft" for belt driven loads
S U would indicate a motor manufactured prior to 1965 meeting previous standards.
S Y indicates a non-NEMA standard mount which may be a special base, flange, or
face and a drawing is required to be sure of the dimensions.
S Z indicates a non-NEMA standard shaft and a drawing is required to be sure of the
dimensions.
S C indicates a standard NEMA face mount having a flat mounting surface machined
on the drive end with holes to allow easy, secure mounting to driven equipment.
S D indicates a standard NEMA flange mount having a flat mounting surface machined
on the drive end with holes to allow easy, secure mounting to driven equipment.
S
H indicates a frame with a rigid base having an F dimension larger than that of thesame frame without the suffix X.
S J indicates a NEMA C Face mount with a threaded shaft for a pump motor.
S JM, JP and JM indicate a close-coupled pump motor with specific dimensions and
bearings. The three designations differ in specific sizes.
S M or N indicates a NEMA mount that has a special flange for direct attachment to
fuel atomizing pumps on oil burners. M indicates a 6 3/4 inch flange while N
indicates a 7 1/4 inch flange.
Insulation Class
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Type of insulation used in a motor depends on the operating temperature the motor will experience.
Standard NEMA insulation classes are given by alphabetic classifications according to the
maximum temperature rating and include A, B, F, H, or J.
They are an indication of the maximum temperature the motor insulation can withstand
without degrading its life.
S Class A insulation was the standard insulation used on older U Frame motors between
1952 and 1964.
S T Frame motors produced since 1964 use class B insulation as the standard.
Do not confuse the NEMA insulation classes with the NEMA motor designs which are also
given by letters.
Insulation temperature charts are used to select insulation that will provide dependable motor life.
Example: A motor operating at 180 Degrees C will have an estimated life of:
300 hours with Class A insulation
1800 hours with Class B insulation
8500 hours with Class F insulation
Tens of thousands of hours with Class H insulation
Horsepower Rating
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The full load output power at the shaft the motor can produce
without reducing its operating life.
If a motor produces more horsepower than it is rated
for, the service life will be reduced.
Motors below 1 horsepower are referred to as
fractional-horsepower motors and motors 1 horsepower
and above are called integral-horsepower motors.
NEMA has established standard power ratings from
fractional to thousands of horsepower.
Standard NEMA Horsepower Ratings
1 through 4000 Hp
1
1.5
2
3
5
7.5
10
15
20
25
30
40
50
60
75
100
125
150
200
250
300
350
400
450
500
600
700
800
900
1000
1250
1500
1750
2000
2250
2500
3000
3500
4000
When an application calls for a
horsepower falling between two sizes,
the larger size is chosen to provide the
appropriate power to operate the load.
Motor and engine manufacturers use different tests and definitions when describing power.
Motors have one power rating: Continuous Brake Horsepower
Engines will have several power ratings.
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R.P.M.
RPM is the rated operating speed of the motor at full load.
Normal operating speeds for 60 hertz and 50
hertz motors vary depending on the number
of poles in the motor stator.
Some motors are dual speed motors and both
the speeds will be given.
The motor may be one of the following
NEMA classifications of speed
characteristics:
Constant Speed Motor:
One in which the speed of normal operation is constant or practically constant.
Examples include synchronous motors, induction motors with small slip design, or a DC
shunt wound motor.
Multi speed Motor:
One which can be operated at any two or more definite speeds, each being independent of the load
power required.
Examples include DC motors with more than two armature windings and AC induction
motors with windings capable of various pole groupings to accomplish the specific differentspeeds.
Varying Speed Motor:
One in which speed varies with the load, ordinarily decreasing as the load increases or increasing as
the load decreases.
Examples include series wound DC or repulsion AC motors.
Adjustable Varying Speed Motor:
One in which speed can be adjusted gradually, but once adjusted for a given load, will vary with the
change in load.
Examples include a wound rotor motor with an adjustable rheostat speed control.
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Duty Rating
Motors are classified according to the length
of time expected to operate under full load.
The motor may be rated as either:
1. Continuous Duty
2. Intermittent Duty
Continuous Duty Motors
Continuous duty rated motors are rated to be
run continuously without any damage or
reduction in life of the motor.
General purpose motors will
normally be rated for continuous duty.
Intermittent Duty Motors
Intermittent duty motors are rated to be run continuously only for short time periods and then must
be allowed to stop and cool before restarting.
It is usually possible to reduce
the size, weight, and cost of a
motor by purchasing an
intermittent duty motor.
Intermittent duty motors are
available with maximum
operating times of 5, 15, 30, or
60 minute duties or times.
These motors are sometimes
used on devices like garbage
disposals or air compressors
where the motor operates for a
short period and shuts off afterthe job is accomplished and will
not be needed for an extended
time period.
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Phase
Phase describes the necessary phase of the electric
power supply required for correct connection and
operation of the motor - Single or Three Phase.
Motors are designed for either single or three
phase operation as indicated on the nameplate.
Single Phase Motors
Single phase motors in general may be operated on one
phase of a three phase power supply with the correct rated voltage.
Single phase motors are used in smaller motor sizes, especially those less than 1 horsepower
or where three phase power is not available.
Single phase motors make up 80 percent of the U.S. motor market and are generally less than
10 horsepower in size unless special equipment or situations are applied.
Advantages of Three Phase Motors
Little or no voltage flicker when starting the motor.
Cost less to purchase than comparable size single phase motors.
Have longer life spans than single phase motors.
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Rated Voltage(s)
This is the electrical supply voltage(s) at which
the motor is rated to operate.
AC motors are designed for optimum
performance with a specific voltage
applied from the electrical system.
NEMA Standard Motor Voltages
Single Phase Motors
115, 230, 115/230, 277, 460, and 230/460
Three Phase Motors up to 125 Hp
208, 230, 460, 230/460, 575, 2300, and 4000
Three Phase Motors above 125 Hp
460, 575, 2300, and 4000 volts
When dealing with motors, it is important to understand the difference between nominal
system and nameplate voltages.
Nominal
SystemVoltage
Nameplate
Voltage
120
208
240
480
600
2400
4160
6900
115
200
230
460
575
2300
4000
6600
Some older NEMA motors rated for 200, 220,
440 or 550 volts are sometimes encountered.
Motors with these markings can safely be
replaced by motors having the current NEMA
markings of 208, 230/460 or 575 volts.
Motors rated 115/230 volts and 230/460 volts
in most cases will operate satisfactorily on a
208 volt system but the torque will be 20 to
25% lower.
Operating below 208 volts may require a 208 Volt (200 Volt) motor or the use of the next
higher horsepower standard voltage motor.
Since line voltage will vary over a period of time due to power system load conditions, a motor must
cope with some voltage variation.
Standard motors are designed to tolerate voltage variations of plus or minus 10 percent.
S A motor with a nameplate voltage of 230 volts could be expected to give satisfactory
performance from 207 volts to 253 volts.
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Hertz or Frequency
Identifies the rated frequency of the power source
to be used in cycles per second.
Motors intended for the North American
market are designed for operation on 60
hertz frequencies.
50 hertz indicates a motor made for export
out of the North American market.
NEMA standards specify motors should
operate satisfactorily under frequency
variations up to + 5% of rated frequency.
Operation outside of this limit results in a substantial speed variation and may cause
overheating and reduced torque.
Current (Amperage) Rating
This is the motors rated current at full load and rated
voltage.
Other terms:
Full Load Amps (FLA)
Running Load Amps (RLA)
The motor will draw the rated current when
producing its rated output power when
supplied its rated voltage
When a motor draws more current than it is
rated, the motor is overloaded unless the motor has a service factor larger than 1.0.
Motor's drawing more current than their rated will generally have their windings damaged
due to the additional heat and the motors life will be reduced.
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Design Code Letter
An alphabetic letter used to indicate the
National Electric Code Design Code letter for
the motor.
When AC motors are started with full
voltage applied, they draw in-rush line
currents substantially greater than their
full load running current rating.
The Code letter of the motor is an
indication of the locked rotor KVA per
horsepower for the particular motor and
is a function of the motors design.
The code letter rating gives a good indication of the starting current a particular motor will draw.
A code letter at the beginning of the alphabet indicates a low starting current and a letter
lower than F indicates a high starting current for the particular motor.
The motor's Code Letter is helpful in determining the maximum rating of the motor's
electrical circuit protection.
A replacement motor should have the same rating as its predecessor or the circuit
fuses/breakers and wire may not be sized appropriately and have to be replaced.
Code Letters for Locked Rotor kVA are as follows:
Code
Letter KVA/Hp
A: 0.00-3.14
B: 3.15-3.54
C: 3.55-3.99
D: 4.00-4.49
E: 4.50-4.99
F: 5.00-5.59
G: 5.60-6.29
Code
Letter KVA/Hp
H: 6.30-7.09
J: 7.10-7.99
K: 8.00-8.99
L: 9.00-9.99
M: 10.00-11.19
N: 11.20-12.49
P: 12.50-13.99
Code
Letter KVA/Hp
R: 14.00-15.99
S: 16.00-17.99
T: 18.00-19.99
U: 20.00-22.39
V: 22.40-AND UP
Starting kVA/HP (from chart) X Motor HP 1000 for single phase
Locked Rotor Amps = ------------------------------------------------------ X or
Rated Volts 577 for 3 phase
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Power Factor
The motor's power factor at rated load and voltage.
Motors are inductive loads and have power factors less than 1.0, usually between 0.5 and
0.95 depending on their rated size.
S The higher the rated horsepower, in general the higher the power factor of the motor.
Most AC motors require reactive power from the supply system to develop magnetic fields.
S Reactive power does not provide any useful mechanical work but is required to make
the motor operate.
S Useful mechanical work is developed from Real Power (kW) supplied by the supply
system and is measured in kilowatts.
S The electrical supply system must provide both Real (kW) and Reactive Power
(kVAR) to operate the motor.
The power factor of induction motors varies with load and drops significantly below 75%
load.
Some utilities charge
penalties if plant power
factor is below a certain
percent.
This gives the customeran incentive to apply
power factor correction
(capacitors).
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Connection Diagram
Connection diagrams can be found on the
nameplate of some motors, or the diagram may be
located inside the motor conduit box or on a special
connection plate.
The diagram will indicate the specific
connections for dual voltage rated motors.
The diagram may also provide the standard
direction of rotation for the motor shaft, clockwise, or counter clockwise.
Unless stated otherwise, rotation is specified from the end view of the shaft extension.
Some motors can operate in either direction depending on how the connections to the motor
are made and this information may also be given on the nameplate.
Ambient Temperature
The abbreviation AMB on a motor nameplate provides the maximum ambient temperature the motor
should be operated within.
Ambient means the temperature of the air surrounding the motor.
In general, maximum ambient temperature for motors is 40 Degrees C or 104 Degrees F
unless the motor is specifically designed for a different temperature and indicates so on the
nameplate.
Operation of a motor at ambient temperatures above that given on the nameplate may or may
not affect the life of the motor depending on whether the motor is operating at or near its
rated full load.
Motors operating at or near rated full load will have reduced life if operated at ambient
temperatures above their ratings.
If the ambient temperature is over 104 degrees F, a higher horsepower motor or a special
motor designed for operation at higher ambient temperatures must be used.
Motors for use in abnormally hot places are usually designed to accommodate the higher
ambient by having a lower winding temperature rise.
If the ambient temperature is above 122 degrees F, special consideration must also be made
of the lubricant.
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Temperature Rise
Temperature rise is the increase in the motors
internal temperature as it operates due to current
flowing through the windings.
The ambient temperature plus the
temperature rise is the maximum temperature
at which the motor should operate at full
load.
It can also be thought of as the amount which
a motor operating under rated conditions, is
hotter than its surrounding temperature.
The ambient temperature has very little, if anything, to do with the motors actual temperature
rise.
Certain inaccessible spots of a motor winding are considered to be the hottest spots of the
insulation system. These areas are called hot spots.
S For the reason a 10 Degrees C allowance is made for uneven heating in the motor
called a hot spot allowance.
S The total temperature rise equals the rise due to the load on the motor plus the hot
spot allowance.
S Generally you do not have any control over temperature rise due to load or hot spot
allowance.
However, you can limit motor temperature and maximize life by selecting a motor that can
produce enough horsepower without being overloaded and by making sure the motor runs in
ambient temperatures at or below the nameplate rating.
A good rule to remember is that for every 10 degrees C the operating temperature increases
over rated temperature, motor life will be cut in half.
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Thermal Protection
Indicates if the motor has its own internal automatic or manual thermal overload protection device.
There are several types of protective devices than
can be built into the motor and used to sense
excessive (overload) temperature rise, and/or current
flow.
These devices disconnect the motor from its power
source if they sense the overload to prevent damage
to the insulation of the motor windings.
This prevents the motor from getting to hot and
damaging the windings or causing a possible fire.
The primary types of thermal overload protectors include automatic and manual reset devices that
sense either current or temperature.
With automatic reset devices, after the motor cools,
this electrical circuit interrupting device
automatically restores power to the motor.
With manual reset devices, the electrical circuit
interrupting device has an external button located on
the motor enclosure that must be manually pressed to
restore power to the motor.
Some low cost motors have no internal thermalprotection and rely on external protection between
the motor and the electrical power supply for safety.
Never bypass a thermal protective device because of nuisance tripping of the motor.
The tripping is generally a sign of some other problem, such as overloading, buildup of dirt
and debris, or lack of proper ventilation.
Manual reset protection should be provided where automatic restart of the motor after it cools down
could cause personal injury should the motor start unexpectedly.
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Efficiency
The efficiency of a motor is the ratio of mechanical power output the motor can produce to the
electrical power input required by the motor.
Think of this as the useful work the motor
produces versus the energy the motor
consumes expressed as a percentage.
Most motors operate near their maximum
efficiency at rated load.
Motor efficiency varies from the nameplate
value depending on the percentage of the
rated load applied to the motor.
NEMA standard MG1-12 provides instructions for manufacturers in establishing the value of
efficiency for a given size and type of motor.
The efficiency given on the nameplate
cannot exceed the nominal (average)
efficiency for a large population of
motors of the same design when tested
by the manufacturer.
Variations in motor efficiency exist
from motor to motor due to
manufacturing tolerances, raw material
variations, and process changes.
It is generally reasonable to expect
difference of + 1% for a motors
efficiency based on the nominal
efficiency on the nameplate.
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Special Order Motors
Electrical motors are classified into several groups depending on the type of service for which they
are designed.
Standard or General Purpose motors
General Purpose motors are designed for general use without restrictions for particular applications
and meet certain specific NEMA standards.
General purpose motors are less expensive, use proven designs and are available on shorter
lead times than other service classifications of motors.
Definite Purpose Motor
A Definite Purpose Motor is designed in standard ratings and with standard operating characteristics
for use under service conditions other than usual or for use on a particular type of application.
Common definite purpose motors include
- automotive industry
- chemical industry
- food processing industry
- farm duty
-other categories.
Special Purpose Motor
A Special Purpose Motor is one with special operating characteristics or special mechanicalconstruction or both which is designed for a particular application and which does not meet the
definition of a general or definite purpose motor.
Special Order Motors
Motors can be ordered with an almost unlimited number of variations to fit special applications
where a standard motor is not suitable.
Each motor supplier is more than happy to provide specific information on availability, lead
time and price for special order motors.