Power Savers Mar2010(1)

7/30/2019 Power Savers Mar2010(1)

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TechGuru

54 Mar ch 2010 electronics for you w w w . e f y M a g . c o M

Shweta DhaDiwal baiD

Do Power SaverS

really Save Power?Mn cmpns fund mk f sm ndd pducs cm s 30-40 p cn cc p, ducng cc .bu cn u s cc puggng n sm dc?

A power saver unit plugged into a wall socket

It is rightly said, Energy saved is

energy produced. Power saver is

a smart attempt in this direction.

The theory behind power savers or

energy savers (used interchangeably

by many people) is foolproof, but there

are a lot of conditions that affect thepractical applications of power saver

devices. Heres what we asked the

manufacturers...

w s p s?

A power saver (PS) device resem-

bles a mosquito-repellent plugin gadg-

et (like All-out or GoodKnight) and is

meant to save power in houses, shops

and small ofces. It is plugged into a

socket to work in parallel with otherappliances connected to the electrical

circuit of an establishment.

w nfs f p s-

s?

Power savers primarily save elec-

trical power. However, these also

improve the quality of input electrical

signal, and thus enhance the life-span

of household appliances.

h d k?

The design of a power saver is

based on the principles of power fac-

tor correction (PFC), harmonic current

lter and surge protection. While PFC

helps in reducing reactive power wast-

age, harmonic reduction improves the

quality of power signal.In the long run, surges may cause

heating and seriously damage the

household devices. The improved

quality of the signal prevents damage

to the transmission line. The circuit of

a power saver is designed to prevent

heat loss by appliances.

w s nsd p s?

The device has a big PFC ca-

pacitor and a current harmonic l-

ter circuit. Some devices also have

metal-oxide varistors (MOVs) that

act as transient suppressors, protect-

ing the circuit from voltage spikes. A

series connected thermal fuse is used

with MOVs to provide protection

in the event of short circuit. Power

savers come with integrated voltage

stabilisation circuit too. A light-emit-

ting diode (LED) is used to indicate

power-on condition.

is g us p ss?

Yes, it is absolutely legal. Using apower saver does not mean ddling


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TechGuru


A typical home electrical circuit with power saver

Table II

Powr Consumption yDiffrnt Dvics

Dvic Wttg Numr of units Tot wttg

Air-conditioner 1.5kW 1 1.5kW

Tubelight 40W 4 160W

... ... ... ...

Tot 2.1 kW

bf csng p s, u nd fguu ss nd nduc ds n u us.

yu mus sm nduc ppncs

p sng nf

with the electricity meter. A power

saver is connected to the electrical

circuit after the meter, which means it

does not hamper or manipulate meter

functioning.

Cn i us n m us s

cc?

Power savers can be used in ats,

houses, shops or small ofces. But

power savings depend on the type of

the load being used in the building.

w g m 30 p cn p

sngs s cmd mnufc-u?

Most companies claim that their

devices can save 30 to 40 per cent of

power. However, the actual savings

are only 5-10 per cent.

w pms n c

sngs dpnd?

The power savings depend on:

Type of house.In old houses, wearand tear in copper wires may result

in current leakage, thus adding to the

power loss. In such houses, power

savers may facilitate better savings.

However, in houses with new wiring,

the percentage saving from power sav-

ers is relatively less.

Type of appliances. More induc-tive appliances in a house means more

power savings. The saving is only in

terms of wastage or reactive power.

There is no reduction in true power

(actual working power) required by

the appliances to function.

Ageing of appliances. Efciencyof any electronic/electrical appliance

decreases with ageing. This also re-

sults in more heat losses. Power sav-

ers show signicant savings with old

appliances.Locality.Areas with high voltage

fluctuations like shops and restau-

rants can gain additional savings from

power savers.

Electricity meter.It also affects theworking of power savers.

Atmosphere.Working of air-condi-tioners and refrigerators depends on

the atmospheric temperature. Thus the

atmosphere plays an important role in

power savings.

w s f cc m-

?

Electricity is not stable, as uc-

tuations occur from the supply side. At

the same time, the load in houses is not

balanced. Meters installed in houses

are either traditional torque-operated

or electronic meters.

The traditional torque-

operated meters are highly

sensitive to spikes, giving

incorrect readings some-

times. Electronic meters,

on the other hand, are moreaccurate. All these factors

inuence the savings from

power savers.

Visit www.derc.gov.

in /E lec t ron icMet ers/

Awareness/FAQs.html#a1

to learn more about meter

readings.

Und cndns

s p s

ffc?

If you have only resis-

tive load (bulbs, iron, geyser, etc), con-

necting a power saver to the electrical

circuit wont give you any signicant

power saving. Even if you add a

tubelight and a fan to these devices,

you wont be able to save much. You

can save only on those devices which

contribute to the inductive load, such

as refrigerators, washing machines,

motors and air-conditioners.

Again, the percentage saving de-pends on the parameters mentioned

earlier. Power savers save only the

power that is wasted or is not useful.

a p ss sd c-

fd?

Power saver devices may not neces-

sarily be tested. However, agencies like

National Test House perform tests and

issue certicates. These tests do not

comment on percentage saving. They

provide only factual readings with or

without the power saver in constant-

load condition.

EFY Lab reviewed the test cer-

tificate of a power saver, which

indicated six per cent savings for a

window air-conditioner through the

power saver.

w dffn ps f p

ss?

Power saver devices come in dif-

ferent kilo-watt (kW) ratings of power

capacity. Commonly available are3 kW, 6 kW, 10 kW and 15 kW. Gener-

Table I

Rsistiv nd Inductiv lodsTyp of od Powr svr exmps

nfit

Resistive No Bulb,geyser,electriciron

Inductive Yes Air-conditioner,refrigerator, waterpump,washingmachine, tubelight


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TechGuru


The theory: How it works

Mostofthehouseholdappliancessuchasrefrigerator,air-conditioner,fan,fluorescenttubelightandmixergrinderareinductiveinnature.InductiveloadscreateaphasedifferencebetweentheACcurrentandvoltage.Thewiresandthetransformersarealsoinductiveinnature.

Inductiveloadsrequirereactivepowertowork,whichincreasesthecurrentthatthesourceprovides.ThiscanbeexplainedveryclearlyfromtheMacsdragginganalogyshowninFig.1.ThetruepowerortheactualpowertodragtheloadiskWinforwarddirection.

Powerfactoristhecosineofthephasedifferencebetweenthecurrentandthevoltage.WhenthevoltageandthecurrentareinphasewitheachotherinanACcircuit,theelectricalenergydrawnfromthesourceisfullyconvertedintoanotherformofenergyintheload,andthepowerfactorisunity.Whenthecurrentlagsthevoltage,theenergyiswastedinreactivepowerandthepowerfactorislessthanunity,makingthesystemlessefficient.

Powerfactorcorrectionisamethodinwhichareactiveloadisintroducedintheoppositedirectiontocanceloutthereactanceoftheinductiveloadbyusingapower-factor-correctioncapacitor.

InIndia,thepowerfactorisusuallyintherangeof0.7-0.8dependingonthehouseandload.ThecapacitorsusedforPFCareaspecialtypeoflow-voltagecapacitors.(PleasereferApril2006issueofEFYfordetailsonPFC.)

Current harmonic reduction and surgeprotection. Power electronic equipment are a

source of current harmonics and electromagneticinterference (EMI). It means that the input-sidecurrentwaveformisdistortedasthesumofmultiplefrequenciesisfedattheinput.Theharmoniccurrentsintroduce losses inevery element of the electricaldistributionsystem.

Theharmonicvoltagesandcurrentsdeterioratethe quality of power and give rise to the followingunacceptableissues:

1.Highvoltageandcurrentdistortion(totalharmonicdistortion)attheload2.Highneutral-to-groundvoltagesattheload3.Heatinglossesintransformers,busduct,feeder,circuitandtheapplianceitself4.Reductioninpoweravailablefromthewalloutlettoabouttwo-third

5.Overratedline-frequencytransformersandDC-sidefiltercapacitorsTherearetwotypesofharmonicfilters:passivefiltersandactivefilters.Passivefiltersareoneormorecircuitscomprisinginductorsandcapacitorsandevenresistors

sometimes.Thevaluesofthesecomponentsaredesignedsuchthattheyremoveparticularfrequencyinsteadoftheentirespectrumofdistortion.Passivefiltersarelessexpensivethanactivefilters.

Activefiltersvirtuallyremoveallthedistortionfromthesystem.Thesecontinuouslymonitorthedistortioninthewaveformandprovidecontrolledcurrentinjectioninordertoremovetheharmonicsbygeneratingasinusoidalcurrentwaveformthatisinphasewiththeinputvoltage.ThefilterdesignisdependentonthekVArequirementoftheload,harmonicprofileoftheloadcurrentandalsotheconfigurationoftheexistingsystem.

Fig. 1: Dragging MACs BMI Walogy

Fig. 2: Utility interface needs harmonic ltering

Fig. 3: Current waveforms

ally, household load does not exceed

15 kW. Therefore a single power saver

can be used with single-phase supply

in houses and shops. For three-phase

connection at a small ofce, three pow-

er savers should be installed separately

in each phase.

h cn i cs p s?

Before choosing a power saver,

you need to gure out the resistive

and inductive loads in your house

(see Table I). You must have some

inductive appliances to avail the

power saving benefit. A process

called energy audit can help you indeciding the power saver capacity

that you need.

Table II shows a sample of the ener-

gy audit that you can do individually.

From this table, you can get a rough

estimate of the total wattage of devices

in your house. The total wattage value

will help you in deciding which power

saver to use.

For example, if you have a total

of 20kW load in your house, of which

approximately 15 kW is from induc-

tive loads mentioned in Table I, you

can use a single power saver of 15

kW. If that is not available, you can

use a combination of 10kW and 6kWpower savers. Using a power saver of

more than 15 kW will not give any ad-

ditional saving.

For a small ofce with three-phase

connection, you can calculate the load

in each phase and repeat the above

process before installing the power

saver.

D i k n pcun

puggng n dc?

Power savers are very easy to in-

stall. However, you must make sure

that the neutral and ground lines are

insulated and there is no loose connec-

tion. Plug the power saver in a socket

that is closest to the mains circuitbreaker.


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TechGuru


w s f-spn f p

s?

The lifespan of power savers de-

pends on the life of PFC capacitors

(measured in the number of burn-

ing hours) used. PFC capacitors are

manufactured by Siemens, ABB, GE,etc. From their datasheets, we found

that the life of a capacitor is 6-8 years.

Some capacitors come with even higher

burning hour ratings.

w nfs?

Power savers reduce the heat-

ing loss in appliances. This helps in

improving their life. Also, the lower

value of current harmonics improves

the quality of signal. This reduces the

carbon emission on the power genera-

tion side. Thus, it is benecial for the

utility company providing electrical

supply. For 1 kW of power, 11 kg of

carbon is emitted.

h muc d s dcs cs?

The range is widefrom Rs 400 to

Rs 1600. This cost is not dependent on

additional features or higher savings.

Rather, it is based on the capacity of

the devices and varies from one brand

to another.

tps n ung gd p

s?

Power savers have been much

hyped through SMS marketing and

telemarketing. Here are a few buying

tips:

1. If you have very few inductive

appliances in your house, power saver

may not be the option for you.

2. Buy the power saver only from a

reputed company.

3. Seek existing customers testimo-

nials/comments.

4. Go for a power saver that comes

with guarantee period exceeding 30

days, as you cannot judge its benetsin less than 30 days.

5. Try buying from a seller who

offers money-back guarantee, as there

are duplicates with just an LED circuit

available in the market.

6. If you have a small ofce and a

three-phase supply, the power saver

may be effective.

w fm cn i u p

s?

Visit www.eleb2b.com and select

the section for domestic power saver

manufacturers. You will get the list of

all the manufacturers along with their

contact details.

The author is a senior technology journalist at

EFY

Contributors to this article

1.RaviKumar,E.S.Electronics,Bengaluru

2.DrManishSharma,professor,IITDelhi

3.MilindPatwardhan,professor,VITPune

4.WintechPower,Delhi

5.Buztec,Chandigarh6.ElectronicControlSystem,Nagpur

7.EFYLab,Delhi

email: [email protected]

http://en.futaba.co.jp/index.html

152 Beach Road, #23-08, Gateway East, Singapore 189721,

[email protected]

+91 80 2338 7197,

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Power Savers Mar2010(1)