Why Are Transformer and Alternator Ratings in KVA on Ships

8/17/2019 Why Are Transformer and Alternator Ratings in KVA on Ships

1/18

Why are Transformer and Alternator Ratings

in kVA on Ships?

July 25, 2011 By Sriram Balasubramanian Leave a Comment

On ships, not only transformers, but also generators, protection evices etc!, are mostly rate in"#$! $ motor oes mechanical %or" an thus has mechanical output e&presse in "'! $transformer is a static evice, %hich oes not perform any mechanical %or"! But the mainfunctions are stepping o%n an stepping up of voltage ratings! (nvariably, %hile steppingup)o%n the voltage, it also steps o%n)up the current inversely!

*hus the rating of a transformer can only be e&presse as a prouct of #olts an $mperes +# $-

Amps Rating

*he current flo%ing through the transformer can vary in po%er factor, from .ero / lea +purecapacitive loa- to .ero / lag +/ure inuctive loa- an is ecie by the loa connecte to the

seconary! *he conuctor of the transformer %ining is rate for a particular current beyon%hich it %ill e&cee the temperature for %hich its insulation is rate irrespective of the loa po%er factor!

Voltage Rating

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*he ma&imum voltage %hich the primary %ining can be subecte to, has also a ma&imumlimit! (f the applie voltage to the primary %ining e&cees the ma&imum rate value, then this%ill cause magnetic saturation of the core leaing to istorte output %ith higher iron losses!

*hus consiering both the above ratings, it is usual for transformers to be rate in #$! (t can

further be unerstoo as prouct of voltage +#- an Current +$-! But this oes not mean that onecan apply a lo%er voltage an pass a higher current through the transformer contributing to therate #$ value! *he #$ value is boune iniviually by the rate voltage an rate current!

$ll electrical euipments in connection %ith generation, transmission, istribution of a!c! po%ersuch as alternators, transformers, s%itch gear, cables etc are rate on " #$ basis!

'e "no% that

Cos φ = kW/ k VA.

Or k VA = kW/ Cos φ.

(t is evient from the above euation that the larger the /o%er factor, the smaller is the " #$reuirement of the machinery! *herefore at lo% po%er factors, the 3 #$ rating of the euipmenthas to be mae more, ma"ing the euipment larger an e&pensive!

*hus " #$ rating is so important an it is assigne at the esign stage itself!

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Reasons for Using igh Voltage Systems !n

"oard Ships

July 2:, 2011 By Sriram Balasubramanian Leave a Comment

'e all "no% about the voltages use on boar a ship! (t is usually a ;phase,


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$ny #oltage use on boar a ship if less than 1"# +1000 #- then it is calle as L# +Lo% #oltage-system an any voltage above 1"# is terme as =igh #oltage!

*ypical >arine =# systems operate usually at ;!;"# or

( A 2 10


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4 is the resistance of the conuctor!

*hus po%er loss varies suare of the current carrie by the conuctor! (f the supply voltage is::0#, then the current carrie by the conuctor is 0!002/, an if the voltage is raise to


5/18

o, # a-e Repaired y Cellhone

Charger0 1y 1eh

• 'or"ing at home• =ome'or"

• Current *ransformer • Blac"berry enterpriseservers

Jestine Eong F September 1G, 2012 F G2 Comments>ore

#np2t is %%' -olt/3'h4 AC o2tp2t is (.) -5C

*he problem %ith my cellphone charger %as that it ha stop charging the battery of my cellphone! ( haveecie to fi& it on my o%n %ith the help of Jestine Eong /o%er Supply repair boo"6 TR!U167

S!!T#89 A85 R7A#R#89 SW#TC !57 !W7R SU6#7S.

1

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*he charger cover %as opene an (Hm confient that it can be repaire! *he first thing ( have chec"e%as the output voltage %ith a voltmeter! (t reas .ero volt %hich mean there %as a serious problem in thecharger! (t %as uite ifficult to open the cover because the charger esign oes not have any scre%! ( leftno choice an ha to use a hammer together %ith a "nife to force it open!

$fter opening the cover ( coul cleary see that this charger esign %as a ouble sie circuit boar! *hetop parts %ere all conventional parts li"e brige rectifires, filter caps, optoisolator ic ,mosfet, transformer,an shott"y ioe an the bottom circuit %ere all S>I components such as resistors an transistors!

( began to chec" on the conventional components first an ( foun a resistor %ith the value of 10 ohm 1%att %as completely open an this lo% ohm resistor acts li"e a fuse! Besie the fuse, one of the four


7/18

brige rectifiers ioe %as shorte an the part number %as 1:008! ( i chec"e on other parts li"ecapacitors, transformer, >osfet, schott"y ioes an etc %ere all goo!

( believe the shorte rectifier +ioe- raine too much current causing the lo% ohm resistor to opencircuit thus preventing more components to burn! $fter replace the t%o components, the charger starteto %or" again! *he cover %as seale %ith the help of glue! *he cost of repair %as only KSI 0!5 cents $ne% normal charger %oul cost KSI10!00 an the original one is more e&pensive6KSI50!00 probably! (hope this article can be helpful to those %ho %ants to repair their o%n cellphone charger!

r 1eh4ad

#ran

8ote: lease do not attempt to perform the repair ,ork if yo2 do not kno, a"o2t ele;tri;al safety.

(f you have any interesting repair article that you %ant to share to others please o email me!

( encourage you to leave your comments on the post, as %ell as share the post %ith anyone you feel may benefit from it using the social meia buttons belo%6than"s!


8/18

o, to #nstall 7le;troni; Cir;2its on Ship?

>ay 18, 2011 By $nish 1 Comment

'ith increase in moern technology an automation in shipHs machinery an operations,electronic circuits li"e printe circuit boar or /CB along %ith signal transucer antransmission system are popularly use onboar! Since these are very small an vital circuitsthey reuire proper location an precaution for their installation!

What is rinted Cir;2it 1oard or C1?

(n ships, electronic system /CB plate or boar is commonly use as it is compact in si.e aneasy to replace!

/CB is an electrical interconnection of ifferent electronic components using trac"s, signal

traces, conuctive path%ays etc!, an the %hole circuit is supporte mechanically on a small boar!

(t is very important to properly locate the installation of electronic components as they are proneto amage if there is e&cessive change in the surrounings!

#mportant points to "e kept in mind ,hile installing ele;troni; system

• *he electronic circuits get affecte by change in temperature or heat so component li"etransmitter shoul be installe in a place %ith goo ventilation an %ith no gas or steamlea"age!

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9/18

• Cable connecting the electronic component must be installe over perforate plates forgoo ventilation an shoul not lie on the hot surface!

• *he cable use must have proper insulation!

• Circuits li"e /CB have more chance of getting amage %hen e&pose to hightemperature! *herefore, they are installe in 9ngine control room +9C4- an airconitioning is provie in the control room to maintain the temperature of electronic anelectrical components!

• 'hile installing the electronic component, rier or silica gel pac"ets are use in thecontrol bo& to avoi conensation of moisture over the circuit!

• 'ith moisture over the circuit ue to humiity in the atmosphere, the electroniccomponent %ill behave erratic!

• *he bo& or cabinet use to install electronic circuit must be properly secure %ith the

surrounings to avoi vibration!

• #ibration %ill cause loose or brea"ing of contacts!

• $ll the components are to be tightly fitte in the cabinet as else loose fitting may lea tovibration an hence brea"ing of contacts an components!

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10/18

• 9lectronic circuitHs component cable shoul not be in the vicinity of ::0 v high tensioncable!

• ::0 v cable prouce electromagnetic fiel %hich %ill interact %ith the signal of theelectronic circuit an lea to %rong input or output!

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11/18

Understanding the 1asi; Se;tions of Refer Unit

*! Compressor Se;tion

6 Consist of compressor +%ith =!/ s%itch- an po%er cable storage compartment! /o%ertransformer may be an option %here the ship supply iffers!

6 (t also contain moulating an suction solenoi valve +for controlling the uantity of gas flo%-!

6 Safety fittings in the section are6 moisture liui inicator, pressure relief valve, filter rier etc!

6 Safety of the system is further enhance by electronic monitoring %ith the help of follo%ingsensors6 Compressor suction an ischarge sensor, supply air temperature sensor, supplyrecorer sensor, ambient sensor!

%. Condenser Se;tion

6 *he conenser section contains conenser fan an its motor, an air coole conenser coil anconenser saturation sensor!

6 or air coole conenser air is normally pulle from bottom an ischarge hori.ontallythrough centre of the unit!

6 Some units consists of %ater coole conenser )receiver! *his unit is e&pensive!

$.7-aporator Se;tion

6 *his section contains temperature sensing bulb, return recorer bulb sensor an a thermostatice&pansion valve +for flo% of refrigerant an maintenance of insie temperature-!

6 $ssembly consist of evaporator coil an heater, rain pan an heater, efrost an heattransmission s%itches!


12/18

6 *he evaporator fan circulates air throughout the container by pulling air in top of refrigerationunit an irecting air through evaporator coil %here itHs either heate or coole an is thenischarge out at the bottom of refrigeration unit into the container!

(. >resh air ake 2p Vent

6 /urpose of this vent is to provie ventilation for commoities that reuires fresh air circulationan must be close %hen transporting fro.en foos!

6 $ir e&change epens upon static pressure ifferential %hich %ill vary epening upon ho%container is loae!

Safety and !perating re;a2tion

$n inury, no matter ho% small, shoul never go unattene! $l%ays obtain first ai or meicalattention immeiately!

a- $l%ays %ear safety gloves an glasses %hile %or"ing on any unit an also %hen chargingrefrigerant!

b- 3eep han, tools, an clothing clear from evaporator an conenser fan!

c- o %or" shoul be performe on any unit until all circuit brea"er an start stop s%itches areturne off an po%er supply isconnecte!

- Io not bypass any electrical safety evice!

e- 'hen performing arc %eling on unit or conenser, isconnect all %ire harness connectionfrom the moule in control bo&! Io ot remove %ire harness from the moule unless you aregroune to unit frame %ith a static safe %rist strap!

f- (n case of electrical fire, open circuit s%itch an e&tinguish it %ith CO2 e&tinguisher!

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Understanding Capa;ity Control in Ships

Air Conditioning and Refrigeration System

$pril 12, 2012 By $nish Leave a Comment

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13/18

ShipHs air conitioning an refrigeration system helps in lo%ering room temperature an in"eeping perishable foo items an refrigerate cargo at esirable temperature!

$s iscusse in our article about basics of refrigeration plant Construction an 'or"ing ofShips 4efrigeration plant on ships, the reefer an air conitioning systems are installe to hanle

fluctuating loas i!e! they are responsible for maintaining lo% temperature of several rooms orcargo hols at the same time!

*he efficiency of the refer plant epens on its ability to maintain ifferent rooms or hols atifferent temperature!

What is Capa;ity Control?

Capacity control of a refrigeration plant can be efine as a system %hich controls the output of

the plant as per the loa in eman! $s the loa +temperature- of one room is achieve, there %ill be no more nee of the refrigerant for cooling! =ence, the solenoi valve supplying refrigerant tothat room %ill shut! *his functionality is calle capacity control!

*he refrigeration compressor consists of ifferent units %or"ing in parallel to cope up %ith theloa! $s the loa ecreases, the capacity control system cut off one or more units +epeningupon the loa- an maintains the efficiency of the plant by reucing stresses on ifferent parts!

Components and Working of Capa;ity ;ontrol system

*. Compressor l2"e oil p2mp s2pply

%. Capa;ity ;ontrol -al-e

$. Capa;ity ;ontrol reg2lating -al-e

(. Un0loader assem"ly

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14/18

The ;ompressor l2"e oil p2mp supplies oil to all the bearings an one connection is provie tothe capacity control valve!

The ;apa;ity ;ontrol -al-e is provie %ith high pressure oil from the compressor lube oilsupply pump! *his valve has several grooves bore in to its periphery an connecte to the un6

loaer mechanism of ifferent units!

$ spring piston is provie %hich controls the spreaing of high pressure oil supply in to the bore chamber! *he spring piston is presse by the oil supplie through an orifice %hich pushesthe piston an aligns the un6loaer holes, supplying high pressure oil to the un6loaer unit!

The 2n0loader assem"ly comprises of a un6loaer piston hel by a spring! *he un6loaer pistonis connecte to a rotating cam ring having lifting pins attache to th suction valve! *he lifting pins al%ays act on the suction valve i!e! un6loaing the unit at stop conition!


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'hen the bores on control valve aligns %ith the un loaer bores, oil %ill pass an press the un6loaer piston rotating the cam an releasing the un loaer pins from the suction valve!

The ;apa;ity ;ontrol reg2lating -al-e is responsible to control the pressure +opening anclosing of capacity control valve ports %ith un6loaer ports-! (ts one en is connecte to thecran"case an other en to capacity control valve!


16/18

$s the pressure in the cran"case rops ue to reuction in loa, oil in capacity control valve israine into the cran" case leaing to closing of un6loaer ports, lifting of the suction valve, ancutting of the cyliner unit!

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What are the Safety 5e-i;es on the

Refrigeration System of a Ship?

>arch :, 2011 By 3aranC 1 Comment

$ reefer system is the bac" bone of ships carrying refrigerate cargo! $ malfunction of any of thecomponents of the system can lea to egraation an %astage of perishable an col storagecargo incluing provision for a ship! (t is therefore important to maintain an run therefrigeration plant properly to avoi any brea"o%ns!

(n this article %e %ill learn about the safety feature of the refrigeration plant! Before that, youmust rea the construction an %or"ing of the shipHs refrigeration plant!

*o have an efficient an hassle free operation of a shipHs refrigeration plant an its components, agoo maintenance scheule an safety systems are aopte!

$ safety system inclues alarm, cut offs, an trips %hich safeguars the machinery an its partsfrom getting amage!

*he main safeties aopte for refrigeration plants are

• 6o, ress2re or 6 ;2t off *his is a compressor safety %hich cut off the compressor inthe event of pressure rop in the suction line! *he pressure of the suction line iscontinuously sense by the control unit an %hen it goes belo% the set value, %hichmeans the room is properly coole, the L/ cut out %ill auto trip the compressor! 'hen the pressure rises, inicating there is flo% of refrigerant in the line ue to increase in roomtemperature, the L/ s%itch %ill start the compressor!

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• igh press2re or ;2t o2t $s the name suggests, the high pressure cut out activatesan trips the compressor %hen the ischarge sie pressure increases above the limitvalue! *he =/ cut out is not auto reset an has to be one manually! *he reason behin itis to manually atten the fault %hich is leaing to rise in pressure, else this situation canlea to overloaing of compressor parts an may amage the same

• !il differential ;2t o2t *his safety is again for compressor as it is the only machinery inthe circuit having rotational parts %hich reuires continuous lubrication! (n the event oflo% supply or no supply of lube oil to the bearing, the ifferential pressure %ill increasean activates a trip signal to safeguar the bearing an cran"shaft!

• Relief -al-es 4elief valves are fitte in ischarge sie of compressor an %ill lift ansafeguar the compressor in the event of over pressure! One relief valve is also fitte inthe conenser refrigerant line to avoi amage to the conenser if there is high pressure

in the ischarge line!

• Solenoid -al-es >aster solenoi valve is fitte in the common or main line after theconenser ischarge! (t closes %hen compressor stops or trips to avoi over flo% ofrefrigerant in to evaporator! $ll hols or rooms are fitte %ith iniviual solenoi valve%hich control the flo% of refrigerant to that room!

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18/18

• !il heater Oil heater is provie for the compressor cran" case oil an preventscompressor from getting e&cessively col %hich may effect the lubrication of the parts!

Eou may also li"e to rea6'hat are the /erioic Safety 4outines that Shoul be Carrie Out on aShipP

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Why Are Transformer and Alternator Ratings in KVA on Ships