electricmotors pptx

8/10/2019 ElectricMotors pptx

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Flowserve Corporation Proprietary & ConfidentialSystem Specialist Program

Electric Motors


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What is an electric motor?

An electric motor is an electromagnetic devicethat converts electrical energy into mechanical

energy

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Motor parts Enclosure

Stator

Rotor

Bearings

Conduit Box

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Motor Enclosure

Holds parts together Helps with heat dissipation

In some cases, protects internal components

from the environment.


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Rotor

Rotating part of the motor.

Magnetic field from the stator induces an

opposing magnetic field onto the rotor

causing the rotor to push away from the

stator field.


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Bearings

Sleeve Bearings

Standard on most motors

Quiet

Horizontal shafts onlyOil lubricated

Ball (Roller) Bearings

Support shaft in any position

Grease lubricated

Many come sealed requiring no maintenance


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System Specialist Program

How works an electric motor?

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Magnetic Induction


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Operating Principle



Motor vs. Engine

Motors convert electrical energy to

mechanical energy

Enginesconvert chemical energy tomechanical energy



MOTOR TYPES

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Single Phase Motors

Are not self starting

Require a starting mechanism.

The name generally describes itsstarting mechanism.

Split Phase

Capacitor Run

Capacitor Start

Capacitor Start-Capacitor Run

Shaded Pole

Synchronous

Universal

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Capacitor Start / Capacitor Run

Split Phase



Three Phase Motors

The AC induction motor is a rotating electric machine designed to operate from athree-phase source of alternating voltage. The stator is a classic three phase statorwith the winding displaced by 120.

Tree phase power is used where a large quantity of electrical power is requiredsuch as incommercial and industrial applications.



Horsepower

AC motors manufactured in US are generallyrated in horse power. European equipment is

generally rated in kilowatts

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Motor Power Output Power

Horsepower

Amount of power motor can produce atshaft and not reduce life of motor.

Input Power

Kilowatts

Amount of power the motor consumesto produce the output power

Calculating Required Pump Input Power

0.85% is a good

general number

for efficiency



Power Rating

Electric motors offer the

horsepower required to drive a

machine, which is typically

referred to as electric motor load.

The most common equation for

power based electric motors on

torque and rotational speed is:

hp = (torque X rpm)/5,250.

E = Voltage

I = Amperage

Pf = Power factor

1 hp = 746 watts



Operation - speed The speed of the AC motor depends only on three variables:

The fixed number of winding sets (known as poles) built into themotor, which determines the motor's base speed.

The frequencyof the AC line voltage. Variable speed driveschange this

frequency to change the speed of the motor.

The amount of torqueloading on the motor, which causes slip.
http://www.oddparts.com/acsi/defines/poles.htmhttp://www.oddparts.com/acsi/defines/poles.htmhttp://www.oddparts.com/acsi/defines/drive.htmhttp://www.oddparts.com/acsi/defines/torque.htmhttp://www.oddparts.com/acsi/defines/slip.htmhttp://www.oddparts.com/acsi/defines/slip.htmhttp://www.oddparts.com/acsi/defines/torque.htmhttp://www.oddparts.com/acsi/defines/drive.htmhttp://www.oddparts.com/acsi/defines/poles.htmhttp://www.oddparts.com/acsi/defines/poles.htm



Speed vs Torque




Motor Frame Size

The frame size designation provides information about the motor framesize, the mounting type, and the dimensions according to the NEMA

standard.

If the nameplate displays a two digit frame number, then the motor is less

than one horsepower; and the frame has its D dimension (distance from

the center of the drive shaft to the center bottom of the mount)expressed in sixteenths of an inch.

Motors with frame numbers of three digits, indicate a motor of one

horsepower or greater. To calculate the D dimension divide the first two

digits by four. The D dimension of a EF145C frame motor is 14 divided by 4

or 3.5 inches.




A is the outside dimension of the base in the end view.

B is the outside base dimension in the side view.

D is the distance between the center of the shaft and the bottom ofthe feet.

E is measured from the centerline of the shaft to the center of the

mounting holes in the base. F is similar to E, except the F dimensions measures the centerline of

the frame to the center of the mounting holes in the side view.

BA measures the center of the mounting hole nearest to the end ofthe shaft to the beginning of the usable shaft.

U measures the diameter of the shaft. V is the dimension for the usable length of the shaft.

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System Specialist ProgramPage 23




NEMA Motor Frame Dimensions


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Motor Nameplate


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Service Factor

Motor service Factor (SF) is the percentage of overloading the motor can

handle for short periods when operating normally.

Generally, electric motor service factors:

Handle a known overload, which is occasional. Provide a factor of safety where the environment or service condition is not

well defined, especially for general-purpose electric motors.

Obtain cooler-than-normal electric motor operation at rated load, thus

lengthening insulation life.


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Insulation Class

The insulation class describes a motors ability

to withstand temperatures over time


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Motor Design

NEMA

DESIGN

STARTING

TORQUE

STARTING

CURRENT

BREAKDOWN

TORQUE

FULL LOAD

SLIP

TYPICAL

APPLICATIONS

A Normal High High Low Mach. Tools, Fans

B Normal Normal Normal Normal Same as Design "A"

C High Normal Low NormalLoaded compressor

Loaded conveyor

D Very High Low High Punch Press

DESIGN A, B, C, D

FOR AC MOTORSNEMA has standard motor designs

with various torque characteristics to

meet specific requirements posed by

different application loads. The design

"B" is the most common design


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Design Code RatingAC motors that are started at

full voltage will draw a greatercurrent (amps) than during

normal operations. This is

commonly referred to as inrush

current or starting current.

These codes represent a range

of inrush current.


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Temperature Codes


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Standard vs Premium Efficiency


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Voltage


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Power Supply Frequency


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Voltage and Frequency

Induction motors are at times operated on circuits of voltage or frequency other than thosefor which the motors are rated. Under such conditions, the performance of the motor willvary from the rating. The following is a brief statement of some operating results caused bysmall variations of voltage and frequency and is indicative of the general changes producedby such variations in operating conditions.

With a 10 percent increase or decrease in voltage from that given on the nameplate, the heating at rated horsepowerload may increase. Such operation for extended periods of time may accelerate the deterioration of the insulationsystem.

In a motor of normal characteristics at full rated horsepower load, a 10 percent increase of voltage above that givenon the nameplate would usually result in a decided lowering in power factor. A 10 percent decrease of voltage belowthat given on the nameplate would usually give an increase in power factor.

The locked-rotor and breakdown torque will be proportional to the square of the voltage applied.

An increase of 10 percent in voltage will result in a decrease of slip of about 17 percent, while a reduction of 10percent will increase the slip about 21 percent. Thus, if the slip at rated voltage were 5 percent, it would be increasedto 6.05 percent if the voltage were reduced 10 percent.

A frequency higher than the rated frequency usually improves the power factor but decreases locked-rotor torque andincreases the speed and friction and windage loss. At a frequency lower than the rated frequency, the speed isdecreased, locked-rotor torque is increased, and power factor is decreased. For certain kinds of motor load, such as intextile mills, close frequency regulation is essential.

If variation in both voltage and frequency occur simultaneously, the effect will be superimposed. Thus, if the voltage ishigh and the frequency low, the locked-rotor torque will be greatly increased, but the power factor will be decreasedand the temperature rise increased with normal load.


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Coupling

Frame size Shaft sizemotor and pump

Shaft typemotor and pump

Shaft lengthmotor + pump +


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Shaft upShaft Down

Drip covers, shaft down

Slingers, Shaft up

Vents and drainsInternal heaters

Moisture Kills Motors

Are the bearings designed

For the application

Fans vs Pumps


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Questions?

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