EEE Job Interview Question Answer [ Part 3 ]

Question no 1

Determine power factor from 3 phase energy meter where meter reading is  2500 kwh & 1000 kvar.

We know,

tan @ = KVAR/KWH

           =  2500/1000

           = 0.4

We know,

                secØ = ✓1+tan²Ø

                 secØ = ✓1+(0.4)²

                            = 1.07

        Again,

    

               cos Ø = 1/secØ

                           = 1/1.07

                          = .93

 Power factor = 0.93

Question no 2

In a 3 phase system, R = 150A, Ya= 162A, B= 155A, Voltage 400v & PF= 0.98

Determine the Total power.

We know,

In a system 

Average ampere,

                 = (150+162+155)A/3

                = 467A/3

                = 156A

So,

        P = √3VI cosØ

           = 1.732×400×156×0.98

               = 106 KW

EEE Job Interview Question Answer [ Part 1 ]

EEE Job Interview Question Answer [ Part 2 ]

Question no 3

In a load condition, a single phase motor takes 12A current.  Determine its power loss if the Power factor & efficiency 80% 

V   = 230v

Pf  = 0.8

€  = 0.8

So,

         P = V×I×cos∅×€

            = 230×12×.8×.8

            = 1.76 kw Power 

The motor lost 1.76 KW power for its work