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Motors - The Basics Of Motors

















Motors - The Basics Of Motors



It is important to select the motor that will help assure optimum performance of the equipment
to be driven. To do this, a motor must be selected that is capable of starting the equipment,
bringing it up to operating speed, and driving it at the necessary loading speed as long as
required without excessive heating. The following motor specifications should be considered.
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Review the chart below to determine what category of motor is needed.

CATEGORY

COMMON APPLICATIONS COMMON MOTOR TYPES
General Purpose Belt Drive Fans Belt Drive Blowers Pumps Conveyors Machine Tools Compressors Material Handling Split Phase Capacitor Start Three Phase
Definite /
Special Purpose Washdown Hazardous Location Farm Duty Close Coupled Pump Fire Pump Pool & Spa Pump Elevator Duty Gate & Door Commercial Jet Pump Permanent Split Capacitor
(PSC) Split Phase Capacitor Start Three Phase
HVAC Condenser Fan Direct Drive Blower & Fan Belt Drive Blower & Fan Unit Heater Room AC / Fan Coil Evaporative Cooler Hot Water Circulator Oil Burner Unit Bearing Cooling Tower Refrigeration· Air-Circulating PSC Shaded Pole Split Phase Capacitor Start Three Phase
Tip: Some motors can be used for multiple applications
NEMA (National Electrical Manufacturers
Association) along with electric motor member
companies established a NEMA Premium®
energy efficiency motors program to provide
highly energy efficient products that meet the
needs and applications of users based on a
consensus definition of "premium efficiency"
and use of the NEMA Premium® logo for
premium products.
Choosing a motor with the NEMA Premium® logo will identify higher efficient motors
that will save money in total energy operating cost and improve system reliability.

For more information about the NEMA Premium® efficiency motor program, go to
www.nema.org
or
premiummotors.com
.

Click to enlarge this image
Horsepower

Measurement of how much work is done in a specific
amount of time. This value indicates the power output of
the motor and usually is specified as a fraction or in a
whole number. Small motors can be rated in watts. Tip:
Select a motor with equal or greater horsepower to the
existing motor.
Tip: If no HP or Watt rating is available, amp draw (typically
available on the nameplate) provides the next best
characteristic to sizing the motor.
RPM

Revolutions per minute (RPM) indicate how fast the motor
shaft will rotate under the specified load (HP). Multi-speed
motors can be rated either with the RPM and the number of
speeds (1075/3-speed) or with the RPM for each speed.
Poles and RPM are used interchangeably. Reference the
chart below.

Poles
Synchronous
RPM
Typical
Nameplate RPM
2
3600
3000-3450
4
1800
1625-1750
6
1200
1050-1140
8
900
825-850

Tip: Match RPM within 5% of nameplate RPM.
Tip: Remember that the horsepower (HP) rating of the
motor only applies to the high speed of a multi-speed
motor. As the speed is reduced, the horsepower is reduced.
Voltage







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Voltage is the power rating at which the motor is designed to operate. A motor should operate at plus or minus 10% of
nameplate voltage. A 230 volt motor should operate over a range of 207 volts to 253 volts. A slash (/) between listed voltages
indicates there is a different connection for these voltages. A hyphen (-) between voltages listed usually indicates the same
connection is used for these voltages. (No plus or minus 10%.)

Tip: Match to supplied voltage.
Tip: If the supplied voltage is 115, and the replacement motor is 115/230, the motor will work, if connected for 115 volts.
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Frequency/Hertz (Hz)

The term hertz or frequency was formally called cycles and is nearly always 60 hertz in the USA and Canadian applications
Some foreign countries, especially Europe, use 50 hertz power supplies.
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Type/Phase

Select the motor type based on typical characteristics and uses.

Motor Type

HP Range Typical
Nameplate RPM

Typical Characteristics

Typical Uses
Shaded Pole,
Single Phase
Up to
1/2 HP
Multi-Speed, 1050,
1550, 3000 Low efficiency Not for belt drive as a rule Air over design usually required Always single voltage Non-reversible Low starting torque
Small Fans and Blowers, Unit Heaters, Space
Heaters, Humidifiers, Freezer Blowers,
Window Fans, Floor Fans, Portable
Evaporative Coolers
Permanent Split
Capacitor (PSC),
Single Phase
Up to
1 HP
Multi-Speed, 825,
1075, 1625, 3250 Improved efficiency vs. shaded pole Not for belt drive, as a rule Air over design usually required Typically single voltage Low starting torque
Small Mounted Fans, Air Circulators, Blowers,
Room AC and Central AC, Condenser Fans,
Evaporator Fans, Furnace Blowers, Unit
Heaters, Window Fans, Oil Burners, Pool
Pump, Door Operators, Animal Confinement
Fans for: Poultry, Hogs, Cattle
Split Phase,
Single Phase
Up to
1 HP
850, 1140,
1725, 3450 Moderate efficiency Typically used in belt drive applications No capacitor needed for start-up Available in single voltage and dual voltage Generally reversible rotation Medium starting torque
Belted Fans, Blowers, AC Fans, Blowers,
Office Machines, Small Centrifugal Pumps,
Home Appliances, Door Operators, Oil
Burners, Poultry Feeders, Attic Fans, Furnace
Blowers, Small Tools, Lathes
Capacitor Start,
Single Phase
1/6 to
10 HP
850, 1140,
1725, 3450 Improved efficiency vs. split phase Typically used in belt drive applications Capacitor Required Available in single voltage and dual voltage Generally reversible rotation High starting torque
Compressors, Conveyors, Pumps, Augers,
Machine Tools, Grain Stirrers, Ventilation
Fans, Food Equipment, Barn Cleaners,
Vacuum Pumps, Manure Pumps, Milk
Coolers, Elevators, Cattle Feeders
Three Phase
1/4 HP
and Up
850, 1140,
1725, 3450 High to Premium efficiency Used in belt drive and direct drive applications Three phase power required Typically dual voltage Generally reversible rotation High starting torque
Compressors, Conveyors, Pumps, Augers,
Machine Tools, Grain Stirrers, Ventilation
Fans, Food Equipment, Barn Cleaners,
Vacuum Pumps, Manure Pumps, Milk
Coolers, Elevators, Cattle Feeders, Drying
Fans, Gear Motors

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Environment
Environment
Type
Typical Description
Clean, Dry, Indoor,
Non-Hazardous
OAO - Open Air Over
Vent openings in shell and/or end shields must be located in air stream to provide
motor cooling.

ODP - Open Drip Proof
Vent openings that are placed so drops of liquid falling within an angle of 15
degrees from vertical will not affect performance.

TEFC - Totally
Enclosed Fan Cooled
No vent openings in shell or end shield. Includes an external fan that blows
cooling air over the motor frame.
Dirty, Damp,
Outdoor, Non-
Hazardous
TENV - Totally Enclosed
Non Vented
No vent openings in shell or end shield. Depends on convection air for cooling.

TEAO - Totally
Enclosed Air Over
No vent openings in shell or end shield. Depends on airflow from driven device
for motor cooling. Must be loaded in air stream.
Hazardous
Explosion-Proof
TEFC/TENV
No vent openings in shell or end shields. Designed to withstand an internal
explosion of specified gases or vapors and not allow the internal flame or
explosion to escape.
Tip: A totally enclosed motor can replace an open motor assuming other characteristics meet the application requirements.
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Select Mounting

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Mounting is the way a motor mounts to the application. This is usually determined by the application itself, how the motor is to be
used, and where it will be mounted. Below are some of the typical mounting configurations:
RESILIENT or CRADLE BASE

Motor is isolated from base by rubber rings on
the end shield
RIGID or FOOTED BASE

Motor base is welded or bolted directly to motor
shell
YOKE MOUNT

Tabs are welded to bottom of motor shell for
bolting to a fan column or bracket
C-FACE WITHOUT BASE

End shield has holes for mounting, with base
C-FACE WITH BASE

End shield has holes for mounting
RING

Rubber rings on each end shield. No base


STUD

Extended thru-bolts (studs) for mounting


Tip: Man