super efficient motors

8/8/2019 Super Efficient Motors

1/26

SUPER-EFFICIENT MOTORS

Avalanche071

Need of the hour

AUTHORS

VAISHNAVI.V.BICHU (E & E) FARHANA. SOUDAGAR (E & E)

USN2GI05EE042 USN2GI05EE006

[email protected] [email protected]
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]


2/26


Avalanche072

CONTENTS

1.0INTRODUCTION2.0MOTOR UTILITY SEGMENTATION3.0WHAT DOES ENERGY EFFICIENCY MEAN?4.0 TYPES OF LOSSES

4.1POWER LOSS

4.2 MAGNETIC CORE LOSSES

4.3 FRICTIONS AND WINDAGE LOSS

4.4 STRAY LOAD LOSS

5.0 HOW HIGHER EFFICIENCY CAN BE ACHIEVED?

6.0 INNOVATIVE DESIGN

7.0 FACTORS TO BE CONSIDERED FOR ENERGY MANAGEMENT OF MOTORS

8.0 EFFICIENCY CONSIDERATIONS IN MOTOR PURCHASES

9.0 COMMON MISCONCEPTIONS ABOUT ENERGY EFFICIENT MOTORS

10.0 CRITERIA FOR USE OF ENERGY EFFICIENT MOTORS

11.0 STANDARDS PERSPECTIVE TO ENERGY EFFICIENT MOTORS

12.0 MARKET BARRIERS AND SOLUTIONS

13.0 CONCLUSION

REFRENCES


3/26


Avalanche073

ABSTRACT

Power scenario in the country calls forenergy crisis management. Industrialization and growth in

population is creating a void between demand and supply, and this void is deepening day by day. Limited

resources, huge capital investment limits increased generation. Fossil fuel based generation is harming the

environment. Hydel power is capital intensive and posesthreat to the ecological balance . The generating

cost is increasing day by day & thepower tariffs are on the rise. Unless the above crises are properly

managed power scenario will be bleak. Conservation of the energy is the call of the day.

There is a capital investment that can repay many times its original value over the next 20 years. At the

same time, it can improve equipment reliability, reduce downtime and repair costs, and result in lower

releases of carbon dioxide to the atmosphere. The investment is straightforward: install electric motors

having thehighest electrical energy efficiency commensurate with your needs. Energy-efficient motors pay

for themselves in a few years or sometimes even a few months, after which they will continue to pile up

savings worth many times their purchase cost for as long as they remain in service.


4/26


Avalanche074

1.0INTRODUCTION

Until the energy crises in the 1970s, most general-purpose motors were designed to

provide rated output and operating characteristics at reasonable cost, period. Efficient

operation was at best a secondary consideration. As energy prices began rising, however,

manufacturers began promoting improved motors they called "high-efficiency" and

"energy-efficient", although the terms were not specifically defined at the time.

Old-style "standard efficiency" motors remained popular because they generally cost less

than the new models. Purchasing agents were seldom inclined to spend a little more

money up front in order to save on energy costs later on. But today the story is entirely

different. Looking at the power scenario in the country, there exists a huge gap between

the demand & the supply, which is widening. The generating cost is increasing day by

day & the power tariffs are on the rise. This is affecting the profitability of all the

industries. Hence it is a trend in the industry to look for the opportunities of cost

reduction. The major cost components in an industry include material, labour & energy

costs. Material & labour cost reduction has its own limitations & a manufacturer does not

have a direct control many times. But the manufacturer himself can influence the energy

costs through energy conservation measures & effective energy management.


5/26


Avalanche075

2.0 MOTOR UTILITY SEGMENTATION

The figures of the motor purchases in 2003-04 will give an idea of this potential. About 5

million motors accounting to approximately 5 million kW have been sold in 2003-04.

(These figures are as reported by IEEMA & are approximated to round figures). The non-

reporting members also account for an additional 3-4 mil. KW.

Fractional HP motors account for over 85% of volume. These small motors are used

primarily in domestic appliances and are lightly and/or intermittently loaded. As a result

there is little potential for cost-effective energy savings. Direct current (DC) motors have

applications in the industrial sector. There are few DC motors in-service and most are

being phased out in favour of alternating current (AC) motors with inverter drive

systems. AC low-tension (or low voltage) motors are used by all end-user segments and

represent largest market, following fractional horsepower motors. AC high-tension (high

voltage) motors are used in the industrial sector and are designed for specific

applications. AC low-tension motors can be further classified into squirrel cage and slip

ring (wound rotor) motors. Slip ring motors are designed for specialized applications and

are limited in number.


6/26


Avalanche076

Fig 1

Squirrel cage induction motors are widely used and find applications in all segments of

the industry. The greatest impact from motor efficiency improvements point of view is in

the AC, low-tension, squirrel cage motor ranging in size between 0.75 kW to 37.5 kW.

Motors larger than 37 kW tend to be more efficient and are often customer designed for

specific application


7/26


Avalanche077

Total motors

4357400. Nos.

FHP motors

3900000 Nos.

DC motors

6500 Nos.

AC LT motors

450000 nos.

AC HT motors

900 Nos.

Slip ring

5000 nos.

Squirrel cage

445000 nos.

0.75-7.5kW

350000 nos..

11-37kW

75000 nos..

> 37 kW

20000 nos.

Fig 2

3.0 WHAT DOES ENERGY EFFICIENCY MEAN?

Electric motors are simply devices that convert electrical energy into mechanical energy.

Like all electromechanical equipment, motors consume some "extra" energy in order to

make the conversion. Efficiency is a measure of how much total energy a motor uses in

relation to the rated power delivered to the shaft.

A motor's nameplate rating is based on output horsepower, which is fixed for continuous

operation at full load. The amount of input power needed to produce rated horsepower

will vary from motor to motor, with more-efficient motors requiring less input wattage


8/26


Avalanche078

than less-efficient models to produce the same output. Electrical energy input is measured

in watts, while output is given in horsepower. One horsepower is equivalent to 746 watts.

There are several ways to express motor efficiency, but the basic concept and the

numerical results are the same. For example:

Efficiency, % =746 x Horsepower (output)

x 100Watts (input)

Efficiency, % =Watts (output)

x 100

Watts (input)

The ratio describes efficiency in terms of what can be observed from outside the motor,

but it doesn't say anything about what is going on inside the motor, and it is what's

happening inside that makes one motor more or less efficient than another. For example,

we can rewrite the equation as:

Efficiency, % =Watts (output)

X 100

Watts (output) + Watts (Losses)

Or its equivalent,

Efficiency, % =Watts (Input) - Watts (Losses)

x 100

Watts (Input)


9/26


Avalanche079

"Losses" stands for all the energy "fees" the motor charges in order to make its electrical-

to-mechanical energy conversion. Their magnitude varies from motor to motor and can

even vary among motors of the same make, type and size. In general, however, standard-

efficiency motors (pre-EPAct) have higher losses than motors that meet EPAct standards,

while NEMA Premium motors, or better, have lower losses still.

4.0 TYPES OF LOSSES

Energy losses in electric motors fall into four categories:

Power losses

Magnetic core losses

Friction and windage losses, and

Stray load losses.

Power losses and stray load losses appear only when the motor is operating under load.

They are therefore more importantin terms of energy efficiencythan magnetic core

losses and friction and windage losses, which are present, even under no-load conditions

(when the motor is running, of course).

Power losses, also called IR losses, are the most important of the four categories and can

account for more than one-half of a motor's total losses. Power losses appear as heat

generated by resistance to current flowing in the stator windings and rotor conductor bars

and end rings.

Stator losses make up about 66% of power losses, and it is here that motor manufacturers

have achieved significant gains in efficiency. Since increasing the mass of stator


10/26


Avalanche0710

windings lowers their electrical resistance (and therefore reduces IR losses), highly

efficient motors typically contain about 20% more copper than standard efficiency

models of equivalent size and rating.

Fig 3A typical NEMA motor showing the components that can be modified to increase motor e fficiency

Rotor losses, another form of power losses, are also called slip losses because they are

largelybut not entirelydependent on the degree of slip the motor displays. Slip is

the difference in rpm between the rotational speed of the magnetic field and the actual

rpm of the rotor and shaft at a given load.

Where, S = Slip

N = Output speed under load and

Ns = Synchronous (no-load) speed, rpm

S =

Ns - N

Ns


11/26


12/26


Avalanche0712

Fig 5 cross section of a die cast motor rotor

Copper has higher electrical conductivity than aluminum, and it would be an ideal

conductor bar material except for the fact that it is difficult to die cast. A process to

produce die-cast copper rotors has recently been developed and, when fully

commercialized, it will enable the production of motors with even higher efficiencies

than the best models currently available.

The fact that high-efficiency motors tend to have less slip (run faster) than standard-

efficiency motors must be taken into account in certain applications. For e xample, energy

consumption by centrifugal loads such as fans and rotary compressors is proportional to

the cube of rotational speed. If such loads are driven at the higher speed of a low-slip,

high-efficiency motor directly replacing a standard motor, energy consumption can

actually increase. This situation can sometimes be resolved by lowering rotational speed

with a variable-speed drive, gears or pulleys. There are other parameters, such as torque

or starting current, that can vary among motors of the same nominal horsepower. It is

important to properly engineer the application of any motor to the intended task.


13/26


Avalanche0713

Magnetic core losses arise from hysteresis effects, eddy currents and magnetic saturation,

all of which take effect in the steel laminations. Magnetic losses can account for up to

20% of total losses. With proper design, use of better materials and stringent quality

control, these losses can be reduced considerably.

Fig 6 Three different efficiencies for the same horsepower rating. Top: standard-efficiency pre-

EPAct motor; lower left: EPAct -level motor; lower right: NEMA Premium efficiency motor. Notice

that the rotor and stator lengthen (and the amount of copper in the motor rises) as efficiency

increases. (Courtesy: Toshiba)

The most effective means to reduce hysteresis and saturation losses is to utilize steels

containing up to 4% silicon for the laminations in place of lower-cost plain carbon steels.

The better magnetic properties offered by silicon steels can reduce core losses by 10 to

25%. Reducing the laminations' thickness also helps: substituting 26-ga or 29-ga steel for


14/26


Avalanche0714

The 24-ga steel found in standard-efficiency motors lowers core losses by between 15

and 25%. Lengthening the lamination stack, which reduces the flux density within the

stack, also reduces core losses. Eddy current losses can be reduced by ensuring adequate

insulation between laminations, thus minimizing the flow of current (and IR losses)

through the stack.

5.0HOW HIGHER EFFICIENCY CAN BE ACHIEVED

Fig 7

We have from the efficiency definition,

Efficiency = output / input

= Output / (output + losses)


15/26


Avalanche0715

It is evident from the efficiency equation that efficiency will increase if the losses in the

motor are reduced. Hence the designers aim is to reduce the losses while designing the

energy efficient motor.

The different components of the total losses, its contribution & the measures adopted for

its reduction are as under-

Sr. No. Description of losses

% Age of total

losses

Measures adopted for reduction

1

Load losses or Copper

losses a. Stator

b. Rotor

55-60%

a. Suitable selection of copper

conductors for maximum material.

b. Specially designed rotors

2 Core losses 20-25%

Low watt loss material, thinner

laminations & control of process for

burr height.

3 Friction & windage losses 2-10% Optimum fan design

4 Stray losses 4-5%Optimum slot geometry; Minimum

overhang length

Table 1


16/26


Avalanche0716

6.0INNOVATIVE DESIGN

Fig 8

Feature: Top terminal box at DE and parallel cooling fins. Benefit: 40% higher utilization of cooling airflow than conventional design with

side terminal box at the center of the frame and radial cooling fins.

Feature: Small fan diameter with respect to the fan cowl. Benefit: Optimal cooling air flow, lower fan losses and quite operation. Feature: Radial flow straight blade fan. Benefit: Cooling is independent of direction of rotation and motor is suitable for

bi-directional rotation


17/26


Avalanche0717

Feature: Dual mounting holes at NDE. Benefit: Motor of high rating can be retrofitted in the existing foundation. Feature: Staggered skew rotor Benefit: No inherent axial thrust

7.0 FACTORS TO BE CONSIDERED FOR ENERGY MANAGEMENT OF

MOTORS

1. Proper selection of the motor.

The selection of motor as per the load requirements will have the bearing on the

energy consumption in case of a standard motor, as the efficiency tends to drop

marginally at partial loads.

2. Proper supply network.

The end user does not have a control over the supply conditions if he is not having a

captive power plant.

3. Energy efficient product.

However, using an energy efficient motor in the utility segments ranges mentioned above

will give a substantial savings.


18/26


Avalanche0718

8.0 EFFICIENCY CONSIDERATIONS IN MOTOR PURCHASES

Industrial tariff levels have been increasing in the past and are forecast to continue to

increase in the future. Industrial companies, to remain competitive in world markets, will

have to seek greater efficiencies, including motor and motor system efficiency.

Table 2

Energy efficient motors are cost effective. A payback of 15 months is likely based on

economic analysis for a new motor purchase. The analysis evaluated a typical 15 kW, 4-

pole motor, with average operation of 8,000 hours per year, at current industrial tariff

rates. This analysis compared the energy efficient motors with the standard motor. As the

average operating hours and tariff levels increase the payback period declines.

Economic Analysis 15 kW Example

Payback Reduced with Longer Hours, Greater Load

1 5 k W (4 -p o le ) S t a n d a r d E n e r g y E f f i c ie n t

P r ic e ( R s ) : 1 7 , 7 0 0 2 1 ,4 2 0

% E ff ic ie n c y : 89 . 0 % 9 1 .8 %

P r ic e p re m iu m 3 5 4 0

O p e r a t io n - H o u rs 8 0 00 8 0 0 0

E n e rg y R a t e R s .4 / k W h r R s .4 / k W h r

E n e rg y C o s t ( R s / Y r) : 5 ,3 9 ,3 2 6 5 ,2 2 ,8 7 6

A n n u a l S a v in g s : N il R s .1 6 ,4 5 0 .

P a y b a c k f o r p r e m iu m : 2 .5 M

R e c o v e ry o f E n ti re c o s t o f E E M o t o r: 1 .2 5 Y


19/26


Avalanche0719

9.0 COMMON MISCONCEPTIONS ABOUT ENERGY EFFICIENT MOTORS

Many misunderstandings have arisen concerning the characteristics of todays more

efficient motors. Some of them lead to unfair criticism and other equally inaccurate

notions. Lead users to expect more than these motors will delivers.

Misconception 1: An oversized motor is less efficient .

Many authorities continue to stress the need to match motor rating more closely to

actual load horsepower contending that oversized motors are inherently efficient. A

3HP load for example is more efficiently carried by an under loaded 5HP motor than

by a fully loaded 3HP machine

Misconception 2: a moreefficient motor also has high power factor.

Many motor design modifications may be made to increase efficiency. Some of them

will also increase their power factor, where as others will decrease it. Comparing

energy efficient machines with their less efficient predecessors shows that some do

have high power factor, some have lower power factor and some exhibit no change. If

power factor improvement is ever needed, an easy way to get it is with capacitor on

motor circuitAn economical corrective measure that is not available to improve

efficiency.

Misconception 3: more efficient motors run cooler.

Thats a fallacy. So is the reverse proposition. Cooler motors must be more efficient.

Temperature and heat is not the same thing so they should not be confused with each

other. Temperature ratings for insulation systems or motors are the same regardless of

motor efficiency.


20/26


Avalanche0720

Misconception 4:An energy efficient motor develops less torque and may not

accelerate the load .

Lower rotor resistances, often used to achieve higher efficiencys, thus tend to reduce

motor accelerating torque, but its not the only influence. And the expected amount of

torque reduction is seldom harmful except for load such as full conveyors.

10.0 CRITERIA FOR USE OF ENERGY EFFICIENT MOTORS

It is a common notion that energy efficient motors are exorbitantly costly. It is a myth.

Actually they are about 15-20% costly. But the savings accrued ensures better payback

periods & the extra investment is justified.

There are three major criteria to be considered while using the energy efficient motors

which will have an impact on the payback period

1. New application and / or new installations.This is a most cost effective step. In this case only the differential amount between

E.E motor & standard motor is involved & hence the payback periods are as low as 6-

9 months

2. Replacement of failed motor with an E.E motor.In this case the cost of new motor is compared with the rewinding cost. Hence the

payback periods will be slightly high. It may range from 1-1.5 years. However, it

should be noted that every rewinding deteriorates the motor efficiency & the damage


21/26


Avalanche0721

is cumulative. Hence it is always advisable to replace a failed motor with a better

product.

3. Retrofitting with Energy efficient motor.

This criterion will require a different approach. The identification of the prospective

motor for replacement will depend on lot of factors like load cycle, sizing of motor,

application etc. A number of organizations conduct energy audits through experts in

the field to identify the locations & plan a budget for energy conservation program. A

phased program is chalked out for replacement of existing motors with the E.E

motors.


22/26


Avalanche0722

11.0 STANDARDS PERSPECTIVE TO ENERGY EFFICIENT MOTORS

The graph below gives a comparative picture of specified efficiencies for of motors up to

37kW as per different standards referred inIndia.

50

55

60

65

70

75

80

85

90

95

0.1

0.2

0.5 1. 2. 5. 1

118

. 30

kwratings

Efficie

ncies

IS 12615

IS 8789

IEEMA Std.19-2000

The current Indian Standard IS 8789 addresses efficiency criteria for standard motors in

India. Most of the motor manufacturers in India follow this standard & their efficiency

figures are bound by it. However, all the major ones provide much higher efficient

motors than specified by IS 8789. With the focus on high efficiency motors these days, it

was required that a more stringent standard be brought in to effect. IS 12615 which will

come into effect shortly addresses the issue & is applicable for high efficiency motors. Its

scope, at present covers 4 pole motors up to 37kW.

IEEMA has proposed voluntary standards for E.E motors (No.19 /2000). IEEMA

standard is based on European Union standard & energy Act of USA.


23/26


24/26


Avalanche0724

13.0 CONCLUSION

The market for low-tension motors is vast and complex. In the Industrial sector the

awareness is increasing towards the need to save energy by use of Energy Efficient

Motors. Every element within the chain needs to gear up to push the use of energy

efficient motors & therein gain from the benefits out of it. In the agricultural sector, the

increasing use of submersible pumps present an opportunity to introduce Energy

Efficiency standards. Various institutions and organizations need to synergies their

initiatives & activities under Government thrust to impact a change in the market

Let all of us in the chain contribute our efforts for the cause of energy management

by promoting the use of ENERGY EFFICIENT motors.


25/26


Avalanche0725

REFERENCES

1.Reference to books

Handbook of electrical engineeringS.L.Bhatia EncyclopediaWikepedia

2.Reference to articles

Siemens LtdOut of the world motors Bharat bijlee LtdEnergy efficient motors International copper promotion council (India)Efficiency of motors

3.Reference to an Internet source

www.wapa.gov/pubs/tchbrf/eemotors.htm

www.energy.ca.gov/process/pubs/motors.pdf

www.copper.org/application/electrical/energy/motor_text.html

www.nema.org/gov/energy/efficient/premium

WORD COUNT- ABSTRACT195

PAPER3080
http://www.wapa.gov/pubs/tchbrf/eemotors.htmhttp://www.wapa.gov/pubs/tchbrf/eemotors.htmhttp://www.energy.ca.gov/process/pubs/motors.pdfhttp://www.energy.ca.gov/process/pubs/motors.pdfhttp://www.copper.org/application/electrical/energy/motor_text.htmlhttp://www.nema.org/gov/energy/efficient/premiumhttp://www.nema.org/gov/energy/efficient/premiumhttp://www.nema.org/gov/energy/efficient/premiumhttp://www.copper.org/application/electrical/energy/motor_text.htmlhttp://www.energy.ca.gov/process/pubs/motors.pdfhttp://www.wapa.gov/pubs/tchbrf/eemotors.htm


26/26


super efficient motors

Documents