Energy Savings in Prime Movers - Motors

8/9/2019 Energy Savings in Prime Movers - Motors

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Welcome to the world of Siemens Energy Saving Motors!


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Motor the Main Energy Consumer

The largest user of electrical energy in the industry is anElectric Motor!!!

Electric Motors contribute to almost 74% of industrialelectrical consumption.~ 100% of agricultural power

The integral HP-AC Polyphase motors consume 75% of theenergy consumed by motors


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Energy Consumption of Motors : Application Wise

16 %

18 %

32 %

9%

9%5%

11%

1 Blo wers and Fans 2 Co mpresso rs 3 Pumps 4 Machine To o ls

5 DC Drives 6 Fractio nal HP 7 Other AC Drives

1


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Utility Investment Operating Cost Per Month Operating Cost As % Of Investment

2,50,000 2,000 [ 1%

Maruti Car

Personal Computer 50,000 500 [ 1%

20,000 200 [ 1 %

Washing Machine

20,000 20,000 100 %Electric Motor 20 HP

The operating costs are what count!


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The operating costs are what count!Life cycle costs for a useful life of 3000 Hr/annum


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Energy Efficient Motors How do you identify one?

Surprised?

A motor which consumes the least power is energy efficient, right?

A motor which draws higher current is NOT energy efficient, right?A motor which draws higher no-load current cannot be energy efficient, right?

WRONG!!!


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Energy Efficient Motors The myths dispelled

A motor which consumes the least power is energy efficient, right? Wrong!!!

A motor that is switched off consumes the least power (zero), but since it doesnot produce any output, also has zero efficiency.

Similarly a motor which draws a higher current or a higher no load current doesnot necessarily mean that it is NOT energy efficient as will be proved later.

A higher no-load current only means a poorer power factor. And that does NOT mean a bad motor.


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Power Factor or Efficiency? (1)

Once the magnetic circuit of an induction motor (The slot geometry, no. of slots

and core packet dimensions etc.) is finalised, the efficiency and power factor ofthe motor can be improved at the cost of the other. This means that either themotor has a better power factor at the cost of the efficiency or vice versa.

Since power factor contributes only to the line losses and secondly as it can beimproved externally at the system level, we at Siemens believe in building intothe motor higher efficiency than a higher power factor.

A poor power factor motor draws a higher no-load current. Yes, but we do notintend running motors on no-load, do we?


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A poor power factor motor may even draw a higher current when loaded, but

when it comes to losses or energy efficiencyHigh efficiency Motor Std. Efficiency motor

Motor TypeOutput (kW) 160 160Voltage (V) 415 415Power Factor 0.86 0.9

Efficiency 95.8% 95.3%Rated Current 271 260

11A more currentInput Power (kW) [Power consumption] 167.01 167.89Losses in Motor (kW) [Input - Output] 7.01 7.89

Cable resistance for a length of 100 m at 20C (240mm Al Cable) 0.013 0.013Losses in cable 2.86 2.64

Total Losses 9.87 10.530.66kW more losses

Total Consumption 169.87 170.53kWH Savings (per day) 15.84

Yearly Savings (assuming 300 days, Rs. 4/- per kWH) Rs. 19008


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More reasons why there is no point in concentrating on a higher PF Motor

Motor load may not have much effect on the system power factor, this is truewhen

Most of the induction motor load is represented by large, high speed motors with

inherently better PF and hence PF of a few smaller motors wont mean much.

Motors are only a part of inductive load responsible for PF deterioration, there areother inductive devices as well. [Welding Transformers, chokes, solenoid operatedmechanisms]

High Motor Power factor is wasted if the motor runs much of the time at reduced

load


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Efficiency of Motors

Input Output

= LossesOutput Output

+=

Therefore to increase efficiency reduce losses.

Efficiency for any machine/device is defined as the ratio of output of the

machine to the input to the machine.

Thus by definition, efficiency denoted by the Greek letter can be expressed

as:


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Typical motor loss distribution for a 4 Pole motor (1)

Friction and Windage(Wfw) losses: 15%

Stray Load (Wl)

losses : 5%

Core (Wc) Losses :25%

Stator IR (W s)Losses : 34%

Rotor IR (W r)Losses : 21%


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Efficiency of Motors - How to reduce losses (1a)

Type of Loss Constitutes of Ways to reduce them

Friction Losses Using properly selected bearingsWindage Losses Optimising Fan DesignHysteresis Using low loss Electrical Grade steelEddy Current Losses in Lamination Reduce Lamination thicknessStator Copper Loss Reduce Stator Winding Resistance

Rotor Copper Loss Reduce Rotor Winding Resistance

Mechanical Losses

Iron Losses

Ohmic Losses

Reducing Lamination thickness is not feasible beyond a certain limit due tomechanical strength limitations.Reducing stator and rotor winding resistance results in increase in startingcurrent and decrease in starting torque and increase in speed.


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The Siemens Concept of Effective Efficiency

Generally the efficiency of a motor decreases as the load on the motor

decreases.This requires motors to be designed for specific application.It is advantageous for the client to be able to use the same motor across variousapplications.For this the efficiency should remain constant over a certain load variation.Modern Energy Efficiency criteria insist on FL and 75%FL efficiency beingdeclared.We at Siemens have been concentrating on this right from the beginning.

All our 1LA0 Series Standard Motors have constant efficiency from 100%FL to60%FL.


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Electrical design Philosophy

Maximize Efficiency

kW Efficiency

kVAR Power Factor

kVA

To minimize net cash outflow of customer in way of electricity bills.Since power factor contributes only to the line losses and secondly as it can beimproved externally at the system level, we at Siemens believe in building intothe motor higher efficiency than a higher power factor.


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Energy Efficient Motors Indian Standards

The IS 12615 stipulates efficiency requirements for energy efficient motors. It

covers TEFC motors rated 0.12 kW to 37kW in 4P only.Table 1 of IS:12615

Output Efficiency Output EfficiencykW % kW %0.12 52 5.5 850.18 55 7.5 870.25 580.37 63 9.3 87

0.55 70 11 88

0.75 73 15 891.1 75 18.5 901.5 77 22 90

2.2 80 30 913.7 84 37 91

This standard is under revision and a draft ofIEEMA 19-2000 is already under circulation.

This new standard will cover motors 0.37kW to160kW in 2,4 and 6P and upto 132kW in 8P.

The international Standard CEMEP coversmotors only from 1.1kW to 90kW in 2 and 4P.


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Name Plate - 1LA7 as per eff2

Siemens indicates the efficiency class on the rating plate of the motor.

Efficiency Class on Name Plate

Name Plate - 1LA0 as per eff2


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Background - Introduction of efficiency classes acc. to CEMEPBackground - Introduction of efficiency classes acc. to CEMEPBackground - Introduction of efficiency classes acc. to CEMEPBackground - Introduction of efficiency classes acc. to CEMEP

To implement measures for improving the efficiency levels of electricaldrives. Motive: To reduce the emission of CO 2.

CEMEP prescribes efficiency classification for 2-pole and 4-pole motors in

the power range from 1.1 to 90 kW. Efficiency is subdivided into threeclasses so that 2 characteristics define the three classes:

- "eff1" (High-efficiency motors)

- "eff2" (Improved-efficiency motors)- "eff3" (Standard motors)

1) CEMEP = European Commitee of Manufacturers of Electrical Machines and Power Electronics; Efficiency determined as beforeaccording to EN 60034-2

Efficiency Classification as per CEMEP


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Efficiency Classification as per CEMEP

70

75

80

85

90

95

1 10 100

Trend Trend Trend Trend

[%]

[kW]


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CEMEP- Motors Covered and Efficiency Values

Output 2 Pole 4 PoleEfficiency Class Efficiency Class

kW EFF3 EFF2 EFF1 EFF3 EFF2 EFF1Efficiency in %

1.1 < 76.2 76.2 82.8 < 76.2 76.2 83.81.5 < 78.5 78.5 84.1 < 78.5 78.5 85.02.2 < 81 81.0 85.6 < 81 81.0 86.43.0 < 82.6 82.6 86.7 < 82.6 82.6 87.4

4.0 < 84.2 84.2 87.6 < 84.2 84.2 88.35.5 < 85.7 85.7 88.6 < 85.7 85.7 89.27.5 < 87 87.0 89.5 < 87 87.0 90.1

11.0 < 88.4 88.4 90.5 < 88.4 88.4 91.015.0 < 89.4 89.4 91.3 < 89.4 89.4 91.818.5 < 90 90.0 91.8 < 90 90.0 92.2

22.0 < 90.5 90.5 92.2 < 90.5 90.5 92.630.0 < 91.4 91.4 92.9 < 91.4 91.4 93.237.0 < 92 92.0 93.3 < 92 92.0 93.645.0 < 92.5 92.5 93.7 < 92.5 92.5 93.955.0 < 93 93.0 94.0 < 93 93.0 94.275.0 < 93.6 93.6 94.6 < 93.6 93.6 94.7

90.0 < 93.9 93.9 95.0 < 93.9 93.9 95.0


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Motor Type Frame Output kW Efficiency %1SE0 163-4YK80 160 M 9.3 92.0 1SE0 163-4YL80 160 M 11 92.5 1SE0 166-4YK80 160 L 13 93.0

1SE0 166-4YL80 160 L 15 93.0 1SE0 183-4YL80 180 M 18.5 93.0 1SE0 186-4YL80 180 L 22 93.0 1SE0 207-4YL80 200L 30 93.5

1SE0 220-4YL80 225S 37 94.0 1SE0 223-4YL80 225M 45 94.2

Super Efficiency Motors


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Energy efficient motor replacement program (1)

Determining if your motors are properly loaded

You shouldperform a motor load and efficiency analysis on all of your major workingmotors as part of your preventative maintenance and energy conservation program.It is recommended that you survey and test all motors operating over 1000 hours per

year. Using the analysis results, divide your motors into the following categories:

Motors that are significantly oversized and under loadedreplace with moreefficient, properly sized models at the next opportunity , such as scheduled plantdowntime. Motors that are moderately oversized and under loadedreplace with moreefficient, properly sized models when they fail. Motors that are properly sized but standard efficiencyreplace most of these withenergy-efficient models when they fail.


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Energy efficient motor replacement program (2)

Determining Motor loading:

Operating efficiency and motor load values must be assumed or based on fieldmeasurements and motor nameplate information. The motor load is typically derived from amotors part-load input kW measurements as compared to its full-load value (when kW orvoltage, amperage, and power factor readings are available).

100 /

1000 / cos3% =

rated

avav

kW I V Loading

Where,

Vav, Iav are the average line voltage and line current across the three phases,kW rated is the nameplate rated kW and is the declared rated efficiency

Beware ! Current is not a reliable measure of loading of a motor.


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Current is not a very reliable measure of loading of a motor

As you can see that due todrastic drop in PF at partloads, the current does notdrop linearly and henceestimating loading of motor

by measuring currents doesnot give you correct idea ofthe loading.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 20 40 60 80 100

Load (% of rated)

V a

l u e s ( %

o f r a

t e d v

kW % of rated Efficiency % of ratedPF % of rated Current % of rated

Current, Efficiency and PF as %

of rated Vs Load


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Efficiency of rewound motors

Significant increase in motor losses and consequent reduction in efficiency canresult from poor/improper rewinding practice.

Core loss can increase due to damage to insulation of laminationStator copper loss can increase due to use of incorrect wire sizesLosses can also increase due to distortion in air gap

A study reveals that Electrical Consumption can increase by5 8% in small motors and by2 - 3% in large motors


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Precautions while Rewinding a failed Motor

Conduct No load test before and after rewinding

Check Winding Resistance before and after rewinding


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Energy Saving by using Variable Speed Drives (1)

Where can a motor driven by a Variable Speed Drive help in saving energy?

Fans, pumps, blowers etc., where the load varies depending upon the flow rate are themost popular applications which result in energy savings when Variable Speed Drives areused.

Fans & pumps - the requirements: Maintain the set flow rate based on the inputs. The flow rate may vary as per the process demands.

The methods of achieving this are by :1. Conventional methods2. Variable speed drives


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Energy Saving by using Variable Speed Drives (2)

1. Conventional methods :Pumps : valve control (open/close)Fans : dampers/vanes (open/close)

(Inlet/outlet/by-pass)

In this case, the flow control is achieved by diverting / resisting a part of the fluid flow.

The pumping rate does not decrease 1:1 for a decrease in flow rate.

2. By using a variable speed drive:

Fans as well as centrifugal pumps have T N characteristicsSince P N x T, and T N

P N3


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Energy Saving by a VFD Driven Motor (1)

Throttling Element Variable Speed DriveH Delivery head

H 3

H 2

H 1

A 1

A 2

A 3

Resistance tothe flow

Pump/ Compressorcharacteristic

n n

H 3

H 2

H 1

B 1

B 2

B 3

n 2

n 3

Pump / Compressorcharacteristic

H Delivery head


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Throttling Element Variable Speed Drive

P 1

P 2

P 3

Q 3 Q 2 Q 1

Quantity of flow Q

Power input

Pump / CompressorpowerP

P 1

P 2

P 3

Q 3 Q 2 Q 1

Pump / Compressorpower P


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Throttling Element Variable Speed Drive

P 2

P 3

P 2

P 3

Pump / Compressorpower P

EnergySavings

Q 3 Q 2 Q 1Quantity of flow Q

If you want 60% FlowBy conventionalthrottling method,

energy consumed wouldbe between 60-65%.By Speed reductionmethod energy

consumed would bearound 21.6%

A straight saving ofaround 40%!!!


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Vote of thanks

Thank You !

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Energy Savings in Prime Movers - Motors