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Home / Technical Articles / Electrical Thumb Rules You MUST Follow (1)
Electrical Thumb Rules You MUST Follow (Part 1)
Electrical Thumb Rules You MUST Follow (Part 1)

Electrical Thumb Rules For:

Cable Capacity

  • For Cu Wire Current Capacity (Up to 30 = 6X Size of Wire in
    Ex. For 2.5 = 6×2.5 = 15 Amp, For 1 = 6×1 = 6 Amp, For 1.5 = 6×1.5 = 9 Amp
  • For Cable Current Capacity = 4X Size of Cable in, Ex. For 2.5 = 4×2.5 = 9 Amp.
  • Nomenclature for cable Rating = Uo/U
  • where Uo = Phase-Ground Voltage, U = Phase-Phase Voltage, Um = Highest Permissible Voltage

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Current Capacity of Equipment

  • 1 Phase Motor draws Current = 7Amp per HP.
  • 3 Phase Motor draws Current = 1.25Amp per HP.
  • Full Load Current of 3 Phase Motor = HPx1.5
  • Full Load Current of 1 Phase Motor = HPx6
  • No Load Current of 3 Phase Motor = 30% of FLC
  • KW Rating of Motor = HPx0.75
  • Full Load Current of equipment = 1.39xKVA (for 3 Phase 415Volt)
  • Full Load Current of equipment = 1.74xKw (for 3 Phase 415Volt)

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Earthing Resistance

  • Earthing Resistance for Single Pit = 5Ω, Earthing Grid = 0.5Ω
  • As per NEC 1985 Earthing Resistance should be < 5Ω.
  • Voltage between Neutral and Earth <= 2 Volt
  • Resistance between Neutral and Earth <= 1Ω
  • Creepage Distance18 to 22mm/KV (Moderate Polluted Air) or
  • Creepage Distance = 25 to 33mm/KV (Highly Polluted Air)

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Minimum Bending Radius

  • Minimum Bending Radius for LT Power Cable = 12 x Dia of Cable.
  • Minimum Bending Radius for HT Power Cable = 20 x Dia of Cable.
  • Minimum Bending Radius for Control Cable = 10 x Dia of Cable.

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Insulation Resistance

  • Insulation Resistance Value for Rotating Machine = (KV+1) MΩ.
  • Insulation Resistance Value for Motor (IS 732) = ((20xVoltage (L-L)) / (1000+ (2xKW)).
  • Insulation Resistance Value for Equipment (<1KV) = Minimum 1 MΩ.
  • Insulation Resistance Value for Equipment (>1KV) = KV 1 MΩ per 1KV.
  • Insulation Resistance Value for Panel = 2 x KV rating of the panel.
  • Min Insulation Resistance Value (Domestic) = 50 MΩ / No of Points. (All Electrical Points with Electrical fitting & Plugs). Should be less than 0.5 MΩ
  • Min Insulation Resistance Value (Commercial) = 100 MΩ / No of Points. (All Electrical Points without fitting & Plugs).Should be less than 0.5 MΩ.
  • Test Voltage (A.C) for Meggering = (2X Name Plate Voltage) +1000
  • Test Voltage (D.C) for Meggering = (2X Name Plate Voltage).
  • Submersible Pump Take 0.4 KWH of extra Energy at 1 meter drop of Water.

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Lightning Arrestor

Arrestor have Two Rating:

  1. MCOV=Max. Continuous Line to Ground Operating Voltage.
  2. Duty Cycle Voltage. (Duty Cycle Voltage > MCOV).

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  • Current Rating of Transformer = KVA x 1.4
  • Short Circuit Current of T.C /Generator = Current Rating / % Impedance
  • No Load Current of Transformer =< 2% of Transformer Rated current
  • Capacitor Current (Ic) = KVAR / 1.732xVolt (Phase-Phase)
  • Typically the local utility provides transformers rated up to 500kVA For maximum connected load of 99kW,
  • Typically the local utility provides transformers rated up to 1250kVA For maximum connected load of 150kW.
  • The diversity they would apply to apartments is around 60%
  • Maximum HT (11kV) connected load will be around 4.5MVA per circuit.
  • 4No. earth pits per transformer (2No. for body and 2No. for neutral earthing),
  • Clearances, approx.1000mm around TC allow for transformer movement for replacement.

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Diesel Generator

  • Diesel Generator Set Produces = 3.87 Units (KWH) in 1 Litter of Diesel.
  • Requirement Area of Diesel Generator = for 25KW to 48KW = 56 Sq.meter, 100KW = 65 Sq.meter.
  • DG less than or equal to 1000kVA must be in a canopy.
  • DG greater 1000kVA can either be in a canopy or skid mounted in an acoustically treated room
  • DG noise levels to be less than 75dBA at 1 meter.
  • DG fuel storage tanks should be a maximum of 990 Litter per unit. Storage tanks above this level will trigger more stringent explosion protection provision.

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Current Transformer

Nomenclature of CT:

  • Ratio: input / output current ratio
  • Burden (VA): total burden including pilot wires. (2.5, 5, 10, 15 and 30VA.)
  • Class: Accuracy required for operation (Metering: 0.2, 0.5, 1 or 3, Protection: 5, 10, 15, 20, 30).
  • Accuracy Limit Factor:
  • Nomenclature of CT: Ratio, VA Burden, Accuracy Class, Accuracy Limit Factor.Example: 1600/5, 15VA 5P10  (Ratio: 1600/5, Burden: 15VA, Accuracy Class: 5P, ALF: 10)
  • As per IEEE Metering CT: 0.3B0.1 rated Metering CT is accu­rate to 0.3 percent if the connected secondary burden if imped­ance does not exceed 0.1 ohms.
  • As per IEEE Relaying (Protection) CT: 2.5C100 Relaying CT is accurate within 2.5 percent if the secondary burden is less than 1.0 ohm (100 volts/100A).

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Quick Electrical Calculation

1HP = 0.746KWStar Connection
1KW = 1.36HPLine Voltage = √3 Phase Voltage
1Watt = 0.846 Kla/HrLine Current = Phase Current
1Watt = 3.41 BTU/HrDelta Connection
1KWH = 3.6 MJLine Voltage = Phase Voltage
1Cal = 4.186 JLine Current = √3 Phase Current
1Tone = 3530 BTU
85 Sq.ft Floor Area = 1200 BTU
1Kcal = 4186 Joule
1KWH = 860 Kcal
1Cal = 4.183 Joule

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More Information

Jignesh Parmar

Jignesh Parmar has completed M.Tech (Power System Control), B.E (Electrical). He is member of Institution of Engineers (MIE), India. He has more than 20 years experience in transmission & distribution-energy theft detection and maintenance electrical projects.


  1. PP DEY
    Jul 18, 2023


    • Janaki Prasad
      Dec 08, 2023

      Dear parmar ji,
      You are a great person, of Modi vision, make in India, you are making our indian technicals lerning strong.
      Thanks for best effort.

  2. Paulson John P.
    Jun 23, 2023

    useful for engineers those who works in projects

  3. MK Prakash
    Jan 20, 2023


  4. v prashanth
    Dec 03, 2022


    Nov 08, 2022

    i learned many things by your post. thank you .

    Jun 16, 2022

    Dear sir,
    how to make calculate , cable size 3cx70 sqmm copper pvc insulated double gi strip armoured,

    pl clear this point the conductivity of armour shall not less then 75% of the conductivity of larg core
    how many copper strip use for the conductivity maintain.

  7. Bipin Kumar Singh
    Feb 14, 2022

    What would be current carring capacity of cable in 3phase system?

  8. Satish Wagh
    Feb 01, 2022

    Very good info. for all engineers

  9. Hitendra Marge
    Dec 06, 2021

    Dear sir , need overload current carrying capacity for MV cable with trefoil and flat touching condition with different hours.
    Generally 1 /2/3/4/6/8/10/12/24 hour run with 60% / 75%/90% & 30% overload condition with respectively above mentioned time durations so please how can calculate in easy format.

  10. V Anguchamy
    Nov 18, 2021

    Need Cable current carrying capacity for 3 Phase Cable

  11. Shah
    Jan 18, 2021

    can we use 2 x x 4core and 1 x x 4core power cable instead of 1 x x 4core cable for the connectivity of Diesel Genset (60 KVA) to ATS panel 20 feet apart.
    Please advice…

    • ozigi
      Jan 20, 2021

      2x16mm2 4-core cable which is 2 run of 16mm2 4-core cable is more than enough to connect 60kVA generator to ATS panel
      giving that the generator current = 86.6A

        Mar 18, 2021

        We Have a powerloom factory…with each one has 330 watts 3 phase induction motor voltage -220 freq-50hz
        we have used 4 sq mm for mainline and 2.5sqmm for each motor for 12 motors.
        Can We Connect that same 4 for another 12 motors or we have to add 4 sq mm wire…Help me with your knowledge

    • Prem Singh
      Mar 05, 2021

      We bundled conductors instead of single conductors for ac transmission to reduce skin effect.
      If you provide two cables 4Cx35 Sq mm for one cable 4Cx35 Sq. mm then the system is sufficient and addition of 4Cx10 Sq mm will make it extra strong.

    • Shahzad
      Dec 12, 2021

      Yes you can

  12. Sudhakar
    Dec 11, 2020

    Hi Sir,

    In a substation we use different connectors, like, bus support, couplers, body & cap connector etc, I would like to know what each component is rated for with respect to ampacity. How can we calculate that, is there a way to do that.

  13. Chandraprakash G
    Nov 29, 2020

    Excellent and neat write up, keep the great work !!

  14. murali nagarajan
    Nov 19, 2020

    3phase 40A energy meter 17Nos in one apparetment.
    How much amps switch rating and transformer is required?

  15. saranraj.M
    Sep 17, 2020

    Typically the local utility provides transformers rated up to 1250kVA For maximum connected load of 150kW.
    Power factor*KVA=KW
    But here answer is 150KW
    How it will calculate?

  16. Hemant Samal
    Jul 16, 2020

    Sir, one of my client wants to take connection having his required load 70 KW. In fact I have maximum feeder capacity in the existing panel 100 AMP TPN,MCCB-16 KA. Please suggest me the Feeder specification, so that I can install it in my panel in the spare box. also please eleborate the formula to select.

  17. Rama Sinha Adhikari
    Nov 26, 2019

    Thank you sir. This is very needful to us.

  18. Raj kumar
    Oct 27, 2019


    I need to know the load calculations of
    2core 1sqmm al ar cable = Amps
    1sqmm cu cable = Amps

  19. Subhro
    Jul 24, 2019

    Tor electrical calculation should we take 1HP= 735.5W or 746W

    • Anup Kumar
      Oct 13, 2020


  20. C P
    Jul 15, 2019

    Dear sir
    Twin core flat aluminium pvc insulated cable when we are supply current one core than earthing second core why ?

  21. Abhishek Robinson
    Jul 09, 2019

    Dear sir

    I need your expertise ON TRIPOING OF 220KV EHV transmission line, during lightening.

    Need your help. Can I have your contact number please.

  22. udeerna kV
    Jul 08, 2019

    Very very nice ..very very useful informations &Calculations..thank u very much

    Jul 04, 2019

    For 4Cx 6sqmm cu at cable, you can go with 4Cx 25 sqmm Al AR XLPE cable. And for 3Cx4sqmm you go with 16sqmm if the length is less than 80 to 100mts.

  24. Nanhey lal chauhan
    Jan 13, 2019

    load calculation of3.5*300 sq mm al. cable

  25. Pramod
    Dec 31, 2018

    For single core house wiring to 1.5 sq. Mm. How much current take ?

  26. N Satyanarayana
    Nov 16, 2018

    2800KW, 12Amps 1 phase AC load and distance between incoming supply source to load point is 1500mtr. Cable laid in under ground and HDPE pipe. now can you please suggest cable size and voltage drop calculation

  27. avinash lahane
    Oct 31, 2018

    How to select ct burden when current 1000A and voltage 433 v for metering and capacitor panel realy operating purpose.

    Avinash Lahane

    Oct 14, 2018

    i want to replace 4c*6sqmm copper armed cable with aluminium armed cable can u suggest the thickness of aluminium cable .and also i want to replace 3c*4sq mm copper with aluminium can u please suggest the thicknesses of aluminium cable

  29. Samrat sinh Jhala
    Sep 13, 2018

    How to calculate the full load current of a 3 phase submersible,440V?

  30. somasundaram n
    Sep 04, 2018

    What are the details of motor installed in washing machine to be found out to select strength of wire ie. 2.5 s.qm or 4.5 sq.m or 1.5 sq.m wire to give power supply?

    whether 15 amp.plug and socket can be powered with 1.5 sq.m flexible wire already given for 5 amp socket in the boar or more than 1.5 sq. metre strength wire to be used?

    your kind reply will be useful for me.

    Somasundaram N

  31. Sushil Kumar
    Aug 03, 2018

    Dear Sir
    Can We use 4mmx4core copper armoured cable for 10HP motor coupled with 60LPM hyraulic pump. Application is for chopping/cutting of scrap sheet after blanking

    • Badshah
      Jun 26, 2019

      pls see size of cable. i think it should be higher. you can follow chart for “current vs size of cable”. also different chart for Cu and Al is there

  32. Nilesh
    Jul 20, 2018

    Can I use 25x2x0.75sqmm twisted,shielded cable instead of 50×0.75sqmm shielded cable?
    Application :- I need to transmit 230VAC power from stepper drives to motor.

    Jun 06, 2018


  34. Gnanaguru
    May 16, 2018

    Hi fella,

    I came across this website and got lost in wire Vs cable hurricane :) Later in comments I’ve seen cables AKA “bunch of wires” explanation. Where I got stuck is, according to your statement

    “Cable Current Capacity = 4X Size of Cable in, Ex. For 6 = 4×6= 24 Amp.”

    Yet in the mean time, I’ve witnessed mine wire stood against the current capacity of around 28A for nearly 30minutes!!! Its details are Unsheated,Copper made,No. of wires/Wire dia metre=85/.30. So I’m expecting 6xSize in instead of 4XSize in So I want you to clearly tell me what does wire Vs cable means?

  35. ahmad ayaz
    May 12, 2018

    its really helpful i am very thank full to you for your this kind of act.

  36. ansari
    Mar 30, 2018

    finaly i found nice web site to improve my knowledge. i have to know if i communicates RS485 data with 1.5sq mm 2 core twisted wire without sheld and run the wire 60 mtrs what will happen.
    pls advice

  37. vignesh
    Mar 24, 2018

    Here we using the load 3.6Amps and the same we are using the wire it is ok or we need to change.

  38. Aniesh Mathew
    Mar 18, 2018


    We have the Main Panel MCCB of 400A 4P and the load is 120kVA. The client has provided raw power using 4 core 95Sqmm Aluminum Armoured cable. Please let me know whether the raw power cable is fine for our load?

    Also what is the load 95sqmm can take?

    • Arvind YADAV
      May 12, 2018


      According to load the cable size is good enough, and the cable can carry up to 220A current which means 120Kw or 140KVA

  39. H M Khyruzzaman
    Feb 03, 2018

    Thanks. Very effective information.
    Please give me a clear idea how can I find the contactor rating & over load relay rating for Star-delta Starter. Give me this example for 30kW motor.

  40. Dilip wade
    Dec 30, 2017

    Very useful make PDF and publish for download

  41. Vijay Kumar Job
    Dec 18, 2017

    Please correct 2.5×4 = 9Amps to = 10Amps.
    in cable current capacity thumb rule.

  42. Bello Babayo
    Dec 12, 2017

    Intresting and educative forum for power engineers

  43. Benson Barasa
    Aug 06, 2017

    This forum is indeed amazing quite educative.
    Keep up the good work.
    Thank you.

  44. pn iyengar
    Jul 31, 2017

    Sir, How do the GEB pole lines are identified for phase , neutral and earthing. Reason for my asking is all the lines ( Either 3 or 5 for single and 3 phase ) are same and there is no distinction. Recently in our street light pole tuble light connection, an electricians has given some wrong connection by joining 2 wires either in phase or in neutral. Because of this many of our street people have lost TV, Fridge, AC, Digital wall clock etc. The GEB officials said that Munipal contractor has done the mistake while rectifying the defect in the pole street light. This is the reason why want to know for easy identification of these Phase, Neutral and Earthing wires of GEB Pole. pls. explain with sketch or drawing for easy understanding.

  45. Joseph Puduvala
    Jul 02, 2017

    Dear Sir,

    Would you please advise how can I connect 2 numbers of single phase 3000VA 230V 50 HZ UPS
    in Parallel for redundancy… Appreciate your early response

    Thanks and regards
    Joseph Puduvala

    • vinay kumar
      Nov 15, 2017


      These single phase ups can be connect in parallel only when there Output voltage and frequency are same. so please communicate with service provider to set voltage and frequency of both ups on same value and then your can synchronize the ups.


      Vinay kumar

  46. Arun
    Apr 25, 2017

    It’s awesome page..I love to visit the page but there are no answers posted for all the questions asked by the Engineers..And I would love to join this group on LinkedIn or FB to gain some knowledge about the EEE.Thank you so much guys for your time and patience.
    Anyone please suggest me a book or a site to learn from basics to the core subject of Electrical Engineering including the calculations.
    .You guys TC!!

  47. akshihs
    Apr 21, 2017

    Current capacity of aluminium cable

  48. Sreenath
    Feb 15, 2017

    Hi i have a question
    we require 100KVA DG as part of the factory setup can anyone explain how much capacity of transformer will be needed, is there a possibility to determine the transformer capacity based on the DG or let me know if you need the machinery list thanks in advance

    • vinay kumar
      Nov 15, 2017


      To calculate capacity of Transformer,you have to calculate the load of plant and also consider extension of load in future. then maximum load should be less than 80% of transformer capacity.It does not depend on your D.G availability.


    • Shahzad
      Mar 11, 2018

      In a 3 phase motor we use 10 mm cable one phase taking 40 amp for example how much total current of this motor

  49. Rohan Weerarathna
    Jan 23, 2017

    Can you give motors equations for Induction motors, DC Motors ect.

  50. Yogender
    Jan 05, 2017

    What is equivalent size of cable will be used for earthing of DG sets and Transformer instead of cu /GI strip
    Is considered the same cross sectional area or how to calculate

  51. Mubbashir
    Dec 27, 2016

    Esteemed sir

    I want to know how to calculate current carrying capacity per square mm Arial bunched cable.

  52. Franco George
    Dec 22, 2016

    Sir, please give details about how to bend an earth cable to be connected to diesel generator of 25 KVA. Give me an idea how to bend it.

  53. Muktinath Shil
    Dec 16, 2016

    Dear Sir,
    I want to know what is required AC cable size (in sqmm) for solar on grid 3phase 12.5kW inverter for inverter to ACDB?

    • atul
      May 11, 2018

      4cx16 sqmm Cu.

  54. Ravindra Raghuwanshi
    Dec 06, 2016

    We have infrared lamp resin curing plant & paper dryers. Total load is 330 KW. Connected with neutral and 3 phases i.e.each phase will have a load of 110 kw. Current 500 amp. What should the cable size and 3.5 core or 4 core. We will prefer copper.

  55. Rajendra Singh
    Oct 07, 2016

    how can we have check the copper nd aluminium cable size according to load via formula or trick ?
    this is very urgent for me, pls help me sir ASAP.

  56. M Ajay
    Sep 28, 2016

    Dear Sir,

    your above mentioned information is very useful.But please mention the load capacity of aluminium cables also..for 30sqmm copper cable we can put a load of 120A??

  57. Hasrat ali
    Aug 25, 2016

    Gd evening sir
    Pls told me sir
    How will be calculate cable size in mm^2
    Pls told me a short trik
    For example which size of cable should be use for 2500amp rating braker
    Pls sir as soon as possible rply me

  58. sujith thankachan
    Aug 23, 2016

    Thanks a lot sir
    this helping me more……..

  59. Priyanka Waikar
    Aug 15, 2016

    i just want solution for this. if i want to pass current of 1600 Ampere so what size of cable should i select?? cable size should in MM^2

    • Muhammad Ali Khan
      Aug 21, 2016

      It should be 400 Sq mm

  60. shivam
    Jun 27, 2016

    Sir, can you say that how a dc current of 2.5 amps will flow through a wire of resistance 60 ohms? input is 36 volts 11 ah battery

  61. Rholand Forescal
    Jun 20, 2016

    Sir please tell me why 1hp single phase motor is 7ampere in single phase motor chart in ampere. But if we use the formula in ohms law to get ampere in single phase I = hp / VxExPF we only get only 4.23 ampere when voltage is 230v power factor is 0.9 and i used 0.85 efficiency.. Please teached me how to prove the electrical thumb rules.

  62. Isuru
    May 31, 2016

    what is the difference between “Cu Wire Current Capacity” and Cable “Cable Current Capacity”?

    • pawan bhardwaj
      Aug 29, 2016

      For Cu Wire Current Capacity (Up to 30 = 6X Size of Wire in
      Ex. For 2.5 = 6×2.5 = 15 Amp, For 1 = 6×1 = 6 Amp, For 1.5 = 6×1.5 = 9 Amp
      For Cable Current Capacity = 4X Size of Cable in, Ex. For 2.5 = 4×2.5 = 9 Amp.

  63. gurpreet
    May 28, 2016

    Plz tell me how to calculate size of generator set for a specific submersible pump set i.i for specific hp motor? Thanks alot

  64. Swapnendu Sil
    May 05, 2016

    pls tell me sir what cable needed for 32amp industrial socket and how we can determine if we need aluminium cable or cu cable or need 3 phase or single phase in general?

  65. Gopi nath
    Feb 24, 2016

    Super sir

  66. rudramurthy
    Dec 17, 2015

    7/16 cable size meanes what is the sqmm cable size in 3 phase supply 30kva load

  67. Balu B Nair
    Dec 07, 2015

    wonderful informative portal….!!!

  68. Pradeep Rathi
    Oct 15, 2015

    A perfect compilation. Thanks Jignesh. (Author)

  69. shah faisal
    Sep 29, 2015

    how i find cable for a suitable load like a if load is 23 which cable is-perfect for this load and how i find by formula ?

    • MD kashif
      Nov 17, 2015

      Plz tell me how to tabulate the armoured cable size for a particular load.

  70. gurjit
    Aug 11, 2015


    • Rehan
      Oct 08, 2015

      No Its not enough

      If you are having a single phase meter use 1 no of 4 sq mm Cu wire
      and if you are having a 3 phase meter use 2 nos of 4 sq mm wires

  71. ankesh mishra
    Aug 02, 2015

    Tell me the short cut for calculating load for a flat

  72. Deepak Kumar
    Jul 06, 2015

    Please tell me how to find current rating of the conductor

  73. mohan dass
    Jul 03, 2015

    Can we use 2 run of 25 mm sq instead of 50 mm sq cable of Cu. If yes then tell me full details and If not then tell me also full details.

  74. manish chovatia
    May 21, 2015

    How many distance between transformer and diesel genrator as per ie rules

  75. sowmya
    May 01, 2015

    I have a current transformer with 1 main meter outside the building and a control panel having 5 CT meters with black round coils inside the building. I want to know, A) when current pass through the Transformers, will the current be reduced or be the same and after that B) when current pass through the CT meters with black round coils, will the current be reduced or be the same. C) in the above process will the reading of the main meter be same or different, from the total reading of all the 5 CT meters.

  76. swapneswar pradhan
    Apr 07, 2015

    What is the simple formula for electrical, current , voltage

  77. swapneswar pradhan
    Apr 07, 2015

    Thanks sir u help for electrical problem .

  78. omar
    Feb 08, 2015

    we known low pf increase line current so does it increase kwh reading in metering…but pf varation is related also actually totally in reactive part…so what is the impact of pf in metering.

  79. Bassey Friday
    Jan 31, 2015

    Please .I have a 500KVA what % of load should I load it considering the fact that max load is about 700Amp

    • Etop Inyang
      Aug 22, 2015

      Is your generator sets for emergency supply or prime supply? For Prime you can load up to 100% and 70% for emergency generator sets.

  80. mdmukhter
    Jan 03, 2015

    I want to take part in to the technical debates and weekly technical discussion.

  81. abdelsalam mikky
    Dec 22, 2014

    How diesel engine frame should be grounded (I think shall be two earthing diagonal points ) according to NFPA 70 (NEC), could you please provide the supporting standard cod of this

    • Edvard
      Jan 03, 2015

      Every Genset has predefined points to ground engine frame. Don’t forget to ground gas reservoir if it exist.

  82. madhu
    Nov 18, 2014

    How to calculate Cable sizes for the Below in thumb rule,
    01.Single core cable above 30Sqmm
    02.Three phase cable size.
    Pls send it with a clear Example

  83. rahul
    Oct 15, 2014

    what is maximum distance between VCB panel and transformer at 11 kv voltage supply using HT cable of size 3cX95sqmm. Is it ok that transformer is installed at 150 meter away from VCB panel.

    • ali
      Nov 08, 2014

      minimum 6 mtrs

    Oct 06, 2014


    • kalpesh
      Aug 06, 2015

      Because in 3 phase 4 wire system only unbalance current pass from the nutural so current is never higher then half of the phase current,so purpose of aluminium saving its samller size then phase in power cable of higher size

  85. balu
    Oct 01, 2014

    Dear sir,
    Please send me your mobile number because I talk personally with you so I request you please give me your mobile number

    Vagh Balu R

    • Huj
      Oct 03, 2014

      Dear Jebalu, are ju crazy. There is inernet, no personalities!

  86. Arnel
    Sep 22, 2014

    what is the meaning of 2×6+4 for wire sizing?

  87. R Knight
    Sep 21, 2014

    What do you reckon on SWA 3 phase and Neutral Cable size?

    Circuit 1
    primary fuses, 16A and 20A = 36A
    However, connected load is 9kVA and 3kVA = 17.3A and average consumption is 3kVA and 2kVA respectively, giving ~ 8A

    Circuit 2
    Primary fuses, 40A, 16A, 16A and 16A = 88A
    However, nominal current is 33A, 6A, 8A and 11A, giving ~ 58A

    Circuit 2
    11kw fan with a 32amp supply

    on Cable run of 150m

  88. kushvendra tyagi
    Sep 17, 2014

    If the load requirement is 1200 kva , what kind of independent feeder should be considered , 11th or 33 kv

  89. Glenn
    Sep 03, 2014

    Hi need clarification to choose between 3 core, 3.5 core and 4 core for cable selection application. I know we choose 3.5 core and above in case of unbalanced loads any advice on making selection more clear is greatly appreciated

  90. Thuong.nguyen
    Jul 12, 2014

    1 Phase Motor draws Current = 7Amp per HP.
    Full Load Current of 1 Phase Motor = HPx6
    I think full load current of 1 phase is too high, for examples, in catalog of manufacture, current of 1 phase motor 4HP only about 12A. Moreover, please clarify why percent of draw current and full load current is small (7/6), as i know that factor is 3/1.( In my country, there used 220V for line voltage and 380V for phase voltage). The same question for 3 phase motor.

  91. Muhammad Bilal
    Apr 15, 2014

    What is the difference between line and phase?

    • Ganesh Kaneriya
      Jul 18, 2014

      line to line voltage means voltage between 2 line
      and Phase voltage means voltage between 1 line and neutral

  92. neeraj kumar
    Apr 06, 2014

    thanks 4 d info it was really
    help full we all must share
    these things so we could get best of

  93. Joe C.
    Dec 25, 2013

    Please I have some business proposals for the author.
    Please get in touch with me at [email protected]

  94. Annu
    Oct 28, 2013

    Thanks Dear sharing Such valuable data

  95. nmr
    Oct 03, 2013

    sirs, for aluminium cables and wires current carrying was not indicated in the thumb rules.

  96. aakifnouman
    Sep 02, 2013

    Thank You For This and for those u cant understand this is only a thumb rule just to understand and remember

  97. sumitfloyd
    Sep 02, 2013

    On the section current capacity of Equipments, it is written
    # 1 Phase Motor draws Current = 7Amp per HP.
    # 3 Phase Motor draws Current = 1.25Amp per HP.

    I am not quite clear on these points. Please clarify. Does it mean if we have 3HP single phase motor then it will draw 21Amp current throughout its operation or during its starting?

  98. kriloter
    Aug 28, 2013

    These rules could be a little bit tricky unless you don’t know further connections …
    Not all of them are aplicable in a different distribution systems worldwide, especially constants like •Current Rating of Transformer = KVA x 1.4, etc.
    I suggest author should notice the conditions and input values in which are these rules aplicable and users should modify them according to a specific distribution system.

    • alam
      Mar 14, 2014

      well said mate.!

  99. shaijal100
    Aug 24, 2013

    pls tell me the difference between wire and cable.You mentioned different capacity for cu wire and a cable. You mean cable with aluminium conductor or something else..?Pls tell me..

    • kriloter
      Aug 28, 2013

      cable is bunch of wires :-)

  100. manjunatha_pm
    Aug 24, 2013

    Please give me the solution for below mentioned problem..
    Actually in our plant we having two 500 kva DG set and One dg is new one and other one is old …efficiency is different, so when switch on both and synchronizing.. some problem is occurring and i am not able to synchronizing. .. please give any solution for this problem
    my mail id is [email protected]

    • srinivas subramani
      Nov 19, 2013

      Dear friend, just find the settings configuration in PCC2100 relay for parameter settings:)

  101. ChAliGhafoor
    Aug 23, 2013

    kindly inform frm where did u get this useful information?

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