Home › Electrical Engineering Forum › General Discussion › HOW TO UNDERSTAND ABOUT KWH,KVAH,KVARH,KVA,MD,PF…..HOW TO DECIDE THE MULTIPLICATION FACTOR….HOW TO CALACULATE REQUIRED KVAR? › Re: HOW TO UNDERSTAND ABOUT KWH,KVAH,KVARH,KVA,MD,PF…..HOW TO DECIDE THE MULTIPLICATION FACTOR….HOW TO CALACULATE REQUIRED KVAR?
Spir Georges GHALI said:
iam working as a trainee engineer in a stone crushing plant where it has a load of 750KW AND 630KVA TRANSFRMR….IAM NOT ABLE TO UNDERSTAND THE CONNECTIONS GIVEN IN THE PANELS LIKE NO,NC,CONTACTORS,MCCB,MCB'S,RELAYS,DRIVES……HOW TO UNDERSTAND THE CONNECTION DIAGRAM AND HOW TO TROBLE SHOOOT WHEN A PROBLEM RISES?
HOW TO UNDERSTAND ABOUT KWH,KVAH,KVARH,KVA,MD,PF…..HOW TO DECIDE THE MULTIPLICATION FACTOR….HOW TO CALACULATE REQUIRED KVAR?
PLEASE HELP ME OUT
Daer Mr. Rafi ;
You asked about a lot of points and if we will expailn all in details we need many pages, bu I will try to explain shortly:
NC : Normal Closed, that define the stat on a contact in normal calse ” not working “
NO : Normal Open, that define the stat on a contact in normal calse ” not working “
MCCB : is a Circuit Breaker using to protect a network ( cable ), and contains cormally 2 kind of protections ” Themal & Magnectic Protection “, where there's an adjustable protections and fixed protection, many sizes and frames from ” 16A ” up to ” 1600A”, ans some company have till 3200A, the breaking capacities are from ” 10kA ” up to ” 150kA “, all MCCB are tested accordingly to ” IEC 60947-2 “
MCB : is a Circuit Breaker using to protect a network ( cable ) installe on ” Din-Rail 35mm “, and contains cormally 2 kind of protections ” Themal & Magnectic Protection “, where protections are fixed, 2 sizes from ” 0.5A ” up to ” 125A”, the breaking capacities are from ” 1500A ” up to ” 25000kA “, all MCB are tested accordingly to ” IEC 60898 ” and for breaking capacities can be tested accordingly to ” IEC 60947-2 “
Contactors : they are using to commande ” Running & Stoping ” the motors, there's no protection inside, but the Thermal preotection Relays will be installed with the contactors to realize the necessary protection to the motors. inside of any contactor there's a ” main Contacts ” and ” Auxiliary Contacts ” where the main contacts are used to commande the motors, and the auxiliary for the control circuits, also inside the contactor there a ” Coil ” and by applying the supply voltage to the coil the main contacts close to electrify the motor, and the auxiliary contacts chang their sitation, the nominal currents of contactors are from ” 6A ” uo to ” ≈ 800A “
Drives : I think you mean the drives used to Commande & Protect the motors, if yes, we called ” Variable Speed Drives “, they are Electronic Equipments that can ” Run, Stop, and Chang the speed ” of motors with all necessary protection, and they have also many advantages, the powers oh these drives are from ” 0.5kW ” up to ” 630kW “, and there's, accordinglt the the output torque, 2 kinds ” Standard Torque & High Torque “
There's alos ” Soft Starters ” that we use to ” Run & Stop ” the motors without changing the speed, that means with them the motor should run allways at his normal speed, inside there's in some of them the necessary protection and in others no protection.
I will try to explain the other points in other time.
Dear Mr. Rafi ;
Please, let me know what Multiplication Factor that you asked about to be able to answer.
About the calculation of required kVAR : it's very simple to calculate the ” Q : power of needed capacitors ” by apllying the followinf formula :
Q = P ( tg φ1 – tg φ2 )
– Q : the required capacitors' power in ” kVAR “
– P : the active power in ” kW “
– tg φ1 : tangent φ1 that can can obtain from Cos φ1 ( primery power factor )
– tg φ2 : tangent φ2 that can can obtain from Cos φ2 ( target power factor )